ALUMINUM-AND MOLYBDENUM-COATED NICKEL, COPPER OR IRON CORE FLAME SPRAY MATERIALS
United States Patent 3841901
A flame spray material comprising particles having a nickel, copper or iron core coated with aluminum and molybdenum. Advantageously, based on the weight of nickel, copper, iron, aluminum and molybdenum the nickel, copper or iron is present in about 66 to 97.5 percent, the aluminum in about 2 to 18 percent and the molybdenum in about 0.5 to 16 percent. The material produces a selfbonded wear resistant coating which can readily be machined.
US Patent References:
Flame spraying exothermically reacting intermetallic compound forming composites
Dittrich et al. - May 1967 - 3322515
Flame spraying exothermically reacting intermetallic compound forming composites
Dittrich et al. - May 1967 - 3322515
Inventors:
Novinski, Edward Robert (Mineola, NY)
Harrington, John H. (Warwick, NY)
Harrington, John H. (Warwick, NY)
Application Number:
05/377151
Publication Date:
10/15/1974
Filing Date:
07/06/1973
View Patent Images:
Export Citation:
Assignee:
Metco, Inc. (Westbury, NY)
Primary Class:
Other Classes:
106/1.050, 428/467
International Classes:
C23C4/08; B05B7/20
Field of Search:
117/46FS,105.2 106/1
Primary Examiner:
Lieberman, Allan
Assistant Examiner:
Parr, Suzanne J.
Attorney, Agent or Firm:
Burgess, Dinklage & Sprung
Claims:
What is claimed is
1. A flame spray material in the form of a composite suitable for flame spraying comprising components of aluminum, molybdenum and at least one metal selected from the group consisting of nickel, copper and iron, based on the total weight of nickel, copper, iron, aluminum and molybdenum the nickel plus copper plus iron being present in about 66 to 97.5 percent, the aluminum in about 2 to 18 percent and the molybdenum in about 0.5 to 16 percent.
2. A flame spray material according to claim 1, wherein based on the weight of nickel, copper, iron, aluminum and molybdenum the nickel plus copper plus iron is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
3. A flame spray material according to claim 1, wherein the aluminum and molybdenum are secured to a core of nickel, copper or iron by a binder.
4. A flame spray material according to claim 3, wherein said binder is a varnish.
5. A flame spray material according to claim 4, wherein the composite is a powder, comprises nickel, aluminum and molybdenum, and based on the weight of nickel, aluminum and molybdenum, the nickel is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
6. A flame spray material according to claim 4, wherein the composite is a powder, comprises copper, aluminum and molybdenum, and based on the weight of the copper, aluminum and molybdenum the copper is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
7. A flame spray material according to claim 4, wherein the composite is a powder, comprises iron, aluminum and molybdenum, and based on the weight of the iron, aluminum and molybdenum, the iron is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
8. A flame spray material according to claim 1, in the form of a powder blended with self-fluxing alloy powder, the composite constituting about 5 to 80 percent by weight of the blend.
9. A blend according to claim 8, further containing a metal carbide, the composite constituting about 10 to 20 percent by weight of the blend.
10. In the flame spray coating of a substrate, the improvement which comprises employing a flame spray material according to claim 1.
11. The process of claim 10, wherein based on the weight of nickel, copper, iron, aluminum and molybdenum the nickel plus copper plus iron is present in about 66 to 97.5 percent, the aluminum in about 2 to 18 percent and the molybdenum in about 0.5 to 16 percent.
12. The process of claim 10, wherein based on the weight of nickel, copper, iron, aluminum and molybdenum the nickel plus copper plus iron is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
13. The process of claim 11, wherein the aluminum and molybdenum are secured to a core of nickel, copper or iron by a binder.
14. The process of claim 13, wherein said binder is a varnish.
15. The process of claim 14, wherein the composite is a powder, comprises nickel, aluminum and molybdenum, and based on the weight of nickel, aluminum and molybdenum, the nickel is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
16. The process of claim 14, wherein the composite is a powder, comprises copper, aluminum and molybdenum, and based on the weight of the copper, aluminum and molybdenum, the copper is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
17. The process of claim 14, wherein the composite is a powder, comprises iron, aluminum and molybdenum, and based on the weight of the iron, aluminum and molybdenum, the iron is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
18. The process of claim 10, wherein the flame spray material is in the form of a composite comprising components of aluminum, molybdenum and at least one metal selected from the group consisting of nickel, copper and iron, blended with self-fluxing alloy powder, the composite constituting about 5 to 80 percent by weight of the blend.
19. The process of claim 18, wherein the flame spray material further contains a metal carbide, the composite constituting about 10 to 20 percent by weight of the blend.
20. A flame spray coated article produced by the process of claim 10.
1. A flame spray material in the form of a composite suitable for flame spraying comprising components of aluminum, molybdenum and at least one metal selected from the group consisting of nickel, copper and iron, based on the total weight of nickel, copper, iron, aluminum and molybdenum the nickel plus copper plus iron being present in about 66 to 97.5 percent, the aluminum in about 2 to 18 percent and the molybdenum in about 0.5 to 16 percent.
2. A flame spray material according to claim 1, wherein based on the weight of nickel, copper, iron, aluminum and molybdenum the nickel plus copper plus iron is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
3. A flame spray material according to claim 1, wherein the aluminum and molybdenum are secured to a core of nickel, copper or iron by a binder.
4. A flame spray material according to claim 3, wherein said binder is a varnish.
5. A flame spray material according to claim 4, wherein the composite is a powder, comprises nickel, aluminum and molybdenum, and based on the weight of nickel, aluminum and molybdenum, the nickel is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
6. A flame spray material according to claim 4, wherein the composite is a powder, comprises copper, aluminum and molybdenum, and based on the weight of the copper, aluminum and molybdenum the copper is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
7. A flame spray material according to claim 4, wherein the composite is a powder, comprises iron, aluminum and molybdenum, and based on the weight of the iron, aluminum and molybdenum, the iron is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
8. A flame spray material according to claim 1, in the form of a powder blended with self-fluxing alloy powder, the composite constituting about 5 to 80 percent by weight of the blend.
9. A blend according to claim 8, further containing a metal carbide, the composite constituting about 10 to 20 percent by weight of the blend.
10. In the flame spray coating of a substrate, the improvement which comprises employing a flame spray material according to claim 1.
11. The process of claim 10, wherein based on the weight of nickel, copper, iron, aluminum and molybdenum the nickel plus copper plus iron is present in about 66 to 97.5 percent, the aluminum in about 2 to 18 percent and the molybdenum in about 0.5 to 16 percent.
12. The process of claim 10, wherein based on the weight of nickel, copper, iron, aluminum and molybdenum the nickel plus copper plus iron is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
13. The process of claim 11, wherein the aluminum and molybdenum are secured to a core of nickel, copper or iron by a binder.
14. The process of claim 13, wherein said binder is a varnish.
15. The process of claim 14, wherein the composite is a powder, comprises nickel, aluminum and molybdenum, and based on the weight of nickel, aluminum and molybdenum, the nickel is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
16. The process of claim 14, wherein the composite is a powder, comprises copper, aluminum and molybdenum, and based on the weight of the copper, aluminum and molybdenum, the copper is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
17. The process of claim 14, wherein the composite is a powder, comprises iron, aluminum and molybdenum, and based on the weight of the iron, aluminum and molybdenum, the iron is present in about 73 to 89 percent, the aluminum in about 5 to 15 percent and the molybdenum in about 6 to 12 percent.
18. The process of claim 10, wherein the flame spray material is in the form of a composite comprising components of aluminum, molybdenum and at least one metal selected from the group consisting of nickel, copper and iron, blended with self-fluxing alloy powder, the composite constituting about 5 to 80 percent by weight of the blend.
19. The process of claim 18, wherein the flame spray material further contains a metal carbide, the composite constituting about 10 to 20 percent by weight of the blend.
20. A flame spray coated article produced by the process of claim 10.
Description:
The invention relates to a nickel or copper aluminum flame spray material which is characterized by excellent bonding and superior machinability of coated surfaces.
It is common to line metal surfaces with other metals of different mechanically superior properties to obtain the best properties of both metals, e.g. cylinders in aluminum engine blocks have been lined with iron sheets to give the benefits of the light weight of aluminum and the wear properties of iron. An improvement thereon involved flame spraying the wear surface onto the receiving surface. To ensure a secure bond between substrate and sprayed metal it was customary to prepare the substrate by mechanical roughening. U.S. Pat. Nos. 2,588,421 and 2,588,422 made a further improvement thereon in that molybdenum was first flame sprayed onto the substrate without need for special preparation of the substrate. Thereafter a hard wear surface such as high carbon steel could be sprayed and the laminate would be securely held together.
For certain purposes it was desired that the flame sprayed surface constitute an intermetallic compound. In U.S. Pat. No. 3,322,515 there is described a flame spray composite material whose components exothermically interact with one another when melted so as to form such intermetallic compound which is deposited upon the substrate. The heat generated by the exothermic reaction aids in the bonding. The composite may comprise separate strands of the two components, e.g. a strand of nickel and a strand of aluminum, the strands being simultaneously fed to a flame spray gun. In accordance with a preferred technique one of the components can be coated onto the other, e.g. a wire comprising a nickel core and an aluminum sheath.
These composites functioned in generally satisfactory fashion but had certain significant limitations. One was that spraying of the nickel aluminum composites produced a great deal of smoke, requiring special ventilating measures. This was solved in U.S. Pat. No. 3,338,688 by employing nickel boron along with aluminum as the coating on the nickel core.
There is still one significant requirement which such composites impose where the coated substrate must undergo further mechanical working. Specifically, whether the self-bonded coating was molybdenum or nickel-aluminum, the surface did not have good machinability. Molybdenum is too hard and requires grinding rather than simple machining; grinding is far more expensive with respect to both equipment and labor. Nickel-aluminum produces rapid tool wear and a rough finish, which problems are not overcome even by varying the nickel and aluminum proportions.
It is accordingly an object of the present invention to provide flame sprayable compositions which are self-bonding and which produce coatings which may readily be worked without de-bonding.
A further object of the invention is to produce superior flame sprayed bearing surfaces.
These and other objects and advantages are realized in accordance with the present invention pursuant to which there is provided a self-bonding composite of exothermically interacting metal components comprising aluminum, molybdenum and at least one metal selected from the group consisting of nickel, copper and iron. The resulting coatings are characterized by excellent bonding and superior bearing and wearing surfaces. They can readily be worked either by grinding or machining.
The novel self-bonding clad material may comprise about 66 to 97.5 percent and preferably about 73 to 89 percent by weight of nickel, copper and/or iron. The aluminum may comprise about 2 to 18 percent and preferably about 5 to 15 percent by weight of the total composition. The molybdenum may comprise about 0.5 to 16 percent and preferably about 6 to 12 percent by weight.
The nickel, copper or iron may be present as such or as an alloy with one another optionally containing a minor amount of other ingredients, e.g. up to about 10 or even 20 percent or more by weight of substances such as silicon, boron, chromium, cobalt, etc. The nickel-copper-iron component preferably constitutes a core which is clad with the aluminum and molybdenum. When used in clad-powder form, the composite of aluminum and molybdenum coated nickel-copper-iron particles should have the general overall shape and size of conventional flame spray powders.
The initial nickel-copper-iron particles which constitute the core or nucleus of the composite powders in accordance with the invention should have a size and shape approximating that desired in the end powders as described above. The nickel-copper-iron core or nucleus particles are then coated with the aluminum and molybdenum, the coating being effected by any known coating process, as for example described in U.S. Pat. No. 3,322,515.
Preferably the aluminum and the molybdenum are deposited in finely divided form in a binder on the nickel-copper particles.
The aluminum and molybdenum preferably in as finely divided form as possible, as for example a size of -325 mesh, are mixed in the required proportions with a binder or lacquer so as, in effect, to form a paint in which the aluminum and molybdenum particles correspond to the pigment. The paint is then used to coat the nickel core particles and allowed to set or dry.
The binder material may be any known or conventional binder material which may be used for forming a coating or for bonding particles together or to a surface. The binder is preferably a varnish containing a resin as the varnish solids, and may contain a resin which does not depend on solvent evaporation in order to form a dried or set film. The varnish may thus contain a catalyzed resin as the varnish solids. Examples of binders which may be used include the conventional phenolic epoxy or alkyd varnishes, varnishes containing drying oils, such as tuna oil and linseed oil, rubber and latex binders and the like.
The coating of the nickel-copper-iron core component with the "paint" containing the aluminum and molybdenum may be effected in any known or desired manner, and it is simply necessary to mix the two materials together and allow the binder to set or dry which will result in a fairly free-flowing powder consisting of the nickel-copper-iron core coated with cladding of the aluminum and molybdenum.
The molybdenum powder may be any known powder including molybdenum alloys containing more than 50 percent molybdenum and most preferably is used in a particle size range between -20 and +1 micron.
The powders are sprayed in the conventional manner, using a powder type flame spray gun, though it is also possible to combine the same in the form of a wire or rod, using plastic or a similar binding, as for example polyethylene which decomposes in a heating zone of the gun. When formed as wires, the same may have conventional sizes and accuracy tolerances for flame spray wires and thus, for example, may vary in size between 1/4 inch and 20 gauge.
The spraying is in all respects effected in the conventional manner previously utilized for self-bonding flame spray material, and in particular nickel aluminum composites. Due to the self-bonding characteristics, special surface preparation other than a good cleaning is not required though, of course, conventional surface preparation may be utilized if desired. The powder in accordance with the invention may be flame-sprayed as a bonding coat for subsequently applied flame spray material or any purposes where it is desired to form the nickel-copper aluminide coating containing molybdenum. The composites may furthermore be sprayed in conjunction with, or in addition to, other flame spray materials conventionally used in the art.
When sprayed, the nickel, copper and/or iron and aluminum exothermically react, forming a nickel, copper and/or iron aluminide intermetallic. The molybdenum and aluminum also exothermically react, forming molybdenum aluminide intermetallic. Complex nickel- copper- and/or iron-molybdenum aluminides and alloys may be formed.
The term "composite" as used herein is intended to designate a structurally integral unit and does not include a mere mixture of components which may be physically separated without any destruction of the structure. Thus, in the case of powder, the term "composite" does not include a simple mixture of individual granules of the separate components, but requires that each of the individual granules contain the separate components which will exothermically react, forming intermetallic compounds. In the case of wire, the individual components must be incorporated in a single wire. In the composite the components must be in intimate contact with each other.
In connection with powders, each grain may consist of an aggregate containing the components which will exothermically react, forming the intermetallic compound, but preferably the individual grains of the powder are in the form of a clad composite consisting of a nucleus of one of the components and at least one coating layer of the other components. Alternatively, the composite may consist of separate, concentric coating layers of at least two of the components and a nucleus of the third or even a fourth material.
In the case of wires, the composites may be in the form of a wire having a coating sheath of one material and a core of the others, alternate coating sheaths of two of the components and a core of the third or a fourth material, a wire formed by twisting or rolling separate wire strands of the components, a wire consisting of a sheath of one component and a core containg the other components in powder or compacted form, a wire consisting of a sheath of one component and a core containing a compacted powder mixture of this same component material and other components, a wire consisting of a plastic sheath and a core containing a compacted powder mixture of components, etc.
In order for the wires to be satisfactory for spraying, the same must not cavitate at the tip when heated, and should preferably be capable of forming a pointed or slightly tapered tip when being melted and sprayed. Thus, if the wires have an outer layer or sheath of one component and an inner core of another component, the inner core cannot have a lower melting point that the outer sheath, as otherwise the inner core will initially melt, causing cavitation at the tip. For example, if the wire is in the form of a core with a coating sheath, the coating sheath must be aluminum, as otherwise during the spraying operation the wire will initially melt out, causing the cavitation which will interfere with a satisfactory spraying operation. The wire having the melting-point characteristics so as to allow the melting off of the tip without this cavitation is referred to herein and in the claims as "non-cavitating wire."
While the components may be present in the stoichiometric proportions required for the formation of the intermetallic compound, it is, however, possible to also have an excess of one or the other provided the relative amounts are sufficient to release quantities of heat in the formation of the intermetallic compounds.
The clad powders, in accordance with the invention, may be formed in any known or desired manner, including known chemical plating processes, in which coating material is deposited on a seed or nucleus of another material, or in which multiple layers of various materials are built up on the seed material, or in which various materials are co-deposited in a single layer on the seed material.
A mode of forming the clad powders involves the depositing of a metal from a solution by reduction on a seed or nucleus, such as by the hydrogen reduction of ammoniacal solutions of nickel and/or copper and ammonium sulfate on a seed powder catalyzed such as by the addition of anthraquinone. It is also possible to form the coating by other processes, such as coating by vapor deposition, by the thermal decomposition of metal carbonyls, by hydrogen reduction of metal halide vapors, by thermal deposition of halides, hydrides, carbonyls, organometals, or other volatile compounds, or by displacement gas plating and the like.
A preferred and greatly simplified mode of forming the clad powders in accordance with the invention is the depositing of two components as coating in the form of a paint on the third component. Thus two of the components which are to form the coating or cladding, may be dispersed in finely divided form in a binder or lacquer so as, in effect, to form a paint in which this component corresponds to the pigment. The paint is then used to coat core particles of the third component and the binder or lacquer allowed to set or dry. The binder material is preferably a resin which does not depend on solvent evaporation in order to form a dried or set film, and which film will decompose or break down in the heat of the spraying process. The binder, for example, may be a phenolic varnish or any other known or conventional varnish, preferably containing a resin as the varnish solids. The components which are initially mixed with the binder or varnish should preferably be as finely divided as possible, as for example -325 mesh. The other component which constitutes the core should be approximately or only slightly below the particle size ultimately desired for the spray powder. The coating of the core component with the "paint" may be effected in any known or desired manner, and it is simply necessary to mix the two materials together and allow the binder to dry or set, which will result in a fairly free-flowing powder consisting of the core component coated with a cladding of the other component bound in the binder.
The aggregates may be formed by compacting or briquetting the various components into the individual granules, or into larger aggregates and then breaking these aggregates into the granules.
The wires may be formed in the known conventional manner for forming wires with various components as, for example, by shrinking a sheath on a core, by forming the core with powder, by twisting the component wires, followed by rolling, drawing, swaging, or the like if desired.
In accordance with one mode of manufacture, one of the components may be formed into a tube or sheath and filled with a powder of the other components or a powder comprising a mixture of the three components, or containing additional components. The tube ends are then sealed and the wire reduced to the desired wire diameter by swaging, rolling or drawing. Preferably the powder or powder mixture is first compressed into cylindrical briquettes before being placed in the sheath or core. The sealing of the tube ends after loading with the powder or powder mixture can be effected, for instance, by insertion of a plug, for example of the metal of the sheath, by welding, twisting, crimping, or the like.
Powders in accordance with the invention should have the general over-all shape and size of conventional, flame spray powders, and thus for example should have a size between -60 mesh and +3 microns and preferably -140 mesh and +10 microns (U.S. Standard screen mesh size). Most preferably the powder should be as uniform as possible in grain size, with the individual grains not varying by more than 250 microns and preferably 75 microns.
Depending on the particular flame spray process and the desired purpose, the composite powder may be sprayed per se or in combination with other different composite powders, or in combination with other conventional flame spray powders or powder components.
While the powders are preferably sprayed, as such, in a powder type of flame spray gun, it is also possible to combine the same in the form of a wire or rod, using a plastic or similar binder, which decomposes in the heating zone of the gun, or in certain cases the powders may be compacted and/or sintered together in the form of a rod or wire. The wires must have the conventional sizes and accuracy tolerances for flame spray wires and thus for example may vary in size between 1/4 inch and 20 gauge, and are preferably of the following sizes: 3/16 + 0.0005 inch to -0.0025 inch, 1/8 + 0.0005 inch to -0.0025 inch, 11 gauge + 0.0005 inch to -0.0025 inch, and 15 gauge + 0.0001 inch, with a smooth clean finish free from surface marks, blemishes, or defects. The wires are sprayed in the conventional manner, using conventional wire-type flame spray guns.
In combining, in the exothermic reaction, forming the intermetallic compound, the components generate heat in situ in the actual material which is to form at least a part of the coating. This is to be distinguished from flame-spray processes and materials in which heat is generated by a reaction, such as an oxidation reaction in which a foreign and non-metallic element is introduced and in which undesirable components may be produced. Aside from greatly contributing to the thermal efficiency of the process, the heat generated in situ in the formation of the intermetallic compound produces novel results, in many instances forming a denser, more adhering coating, having characteristics of at least a partially fused coating. In many instances the coating has self-bonding characteristics, so that special surface preparation, other than a good cleaning, is not required. The spraying in all other respects is effected in the conventional, well-known manner, using conventional flame spray equipment, and the conventional surface preparation may be utilized, if desired. The composites in accordance with the invention may be sprayed in conjunction with or in addition to other flame spray materials conventionally used in the art, or may be sprayed in combination or conjunction with the others.
The use of the nickel-, copper- and/or iron-aluminum-molybdenum composites, will generally improve the bond of the total sprayed material, and thus of the other component or components to the substrate, sometimes making the mixture self-bonding. The particle bond will be improved and the coating will be denser, so that its porosity may be decreased. In general, as little as about 5 percent by weight of the composites in accordance with the invention will be sufficient to substantially improve the bonding characteristics and decrease the porosity of other flame spray materials, such as conventional flame spray metals, alloys or ceramics. There is, of course, no upper limit on the amount as the composite may be sprayed per se, but generally at least about 20 percent by weight of the other component is required if this component is to have a pronounced effect on the characteristics of the coating. Thus, the novel composite when blended may constitute about 5 to 80 percent by weight of the blend, advantageously about 10 to 50 percent and preferably about 10 to 20 percent.
Representative materials with which the novel composites may be flame sprayed include self-fluxing metal powders as described in U.S. Pat. Nos. 2,875,043, 2,936,224 and 3,305,326 as well as carbides as described in U.S. Pat. No. 3,305,326 and mixtures thereof. Preferably the self-fluxing, spray-weld powders are of the nickel or cobalt type, containing boron and most preferably boron and silicon, as the self-fluxing element. The most preferable spray-weldable, self-fluxing metal powders are of the nickel or nickel-chromium alloy type containing boron and silicon. In addition to the base metal, i.e. the nickel and/or cobalt, and the fluxing element, which is the boron or boron and silicon, the powder may be formed of additional alloy components, as for example up to 20 percent chromium, to impart corrosion and oxidation-resistance, carbon in the amount of not more than a few percent, iron in an amount not exceeding about 10 percent and preferably 5 percent by weight of the total alloy. A typical spray-weldable alloy of the boron nickel type of which the powder is composed may, for example, consist of 0.7 to 1 percent carbon, 3.4 to 4.5 percent silicon, 2.75 to 3.75 percent boron, 3-5 percent iron, up to 18 percent chromium, as for example 16 to 18 percent chromium, with nickel making up the balance.
A typical spray-weld alloy of the cobalt-base type may, for example, contain from 1.5 to 3 percent boron, 0 to 4.5 percent silicon, 0 to 3 percent carbon, 0 to 20 percent chromium, 0 to 30 percent nickel, 0 to 20 percent molybdenum, 0 to 20 percent tungsten, and the balance cobalt.
When the novel composites, optionally blended with a self fluxing metal powder, are further blended with a refractory carbide, such as tungsten carbide, titanium carbide, zirconium carbide, tantalum carbide, columbium carbide, hafnium carbide, chromium carbide or the like, extremely high quality coatings are produced, which are superior in various respects to the conventional carbide coatings.
The carbides used in accordance with this embodiment should have a particle size between about -140 mesh U.S. Standard screen size and 8 microns, and preferably between about -270 mesh and + 15 microns, with the amount of carbide being between about 10-75 percent and preferably 45-55 percent by weight, based on the total powder mixture.
If the refractory carbide powder is in a form so that the refractory carbide is bound in a matrix, as for example a cobalt or nickel matrix containing 5-20 percent by weight of either cobalt or nickel, unusually hard and wear-resistant coatings will be produced which do not contain the individual carbide particles imbedded in a fused matrix, but instead contain alloy phases whose micro-hardness is actually substantially higher than that ordinarily obtained from a bonded carbide.
When the powder, in accordance with the invention, containing this matrix-bonded refractory carbide is plasma-sprayed, the same is self-bonding, so that the conventional surface preparation for flame spraying, as for example a deep surface roughening, is not required.
The carbide coatings formed in accordance with the above are extremely hard and wear-resistant, and may be useful as bearing surfaces, abrasive surfaces, and for any other purpose wherein a working surface requires extremely wear-resistant coating.
The refractory carbide, need not be matrix-bound, but should be a pure crystalline carbide, also having the particle size and used in the amounts indicated above. The crystalline carbide-containing coatings formed in accordance with the invention will have extremely high wear-resistance due to the carbide particles, which are dispersed and tightly bound in the fused coating. Coatings may be used for the same type of applications as mentioned in connection with the coatings formed with the matrix-bound carbide.
The following examples, wherein all parts are by weight unless otherwise expressed, are given by way of illustration and not limitation.
EXAMPLE 1
Finely divided aluminum powder (-325 mesh) was dry blended with different selected powders (-400 mesh) in varying amounts. The powder blend was then admixed with a conventional phenolic varnish having approximately 10 percent solid contents so as to form a mixture having the consistency of heavy syrup and containing about 60 percent by weight of the metal particles. 100 grams of the varnish powder mixture was then added to about 900 grams of nickel powder having a size between about 200-325 mesh and the two were thoroughly mixed, with the mixing continued until the varnish dried, leaving a fairly free-flowing powder in which all of the nickel core particles were clad with a dry film which contained the aluminum particles and other selected particles. The powder was then warmed to about 250°F. to ensure complete drying. The powder was then screened and hand-milled to reduce the same to a -100 mesh powder. The powder was flame-sprayed on a mild steel plate which had been surface cleaned by smooth grinding. The spraying was effected at a distance of 6 inches from the plate, using a powder type flame spray gun as described in U.S. Pat. No. 2,961,335 of Nov. 22, 1960 and sold by Metco, Inc., of Westbury, N.Y., under the trade name "Thermospray" powder gun, Type 5 P. The spraying was effected at a rate of 5 to 10 lbs. of powder per hour, using acetylene gas as the fuel, at a pressure of 11 lbs. p.s.i. gauge and a flow rate of 36 cu. ft./hr., and oxygen as the oxidizing gas at a pressure of 15 lbs. p.s.i. gauge and a flow rate of 30 cu. ft./hr. During the spraying a coating layer was built up to a thickness of between 0.030 and 0.050 inch.
The results obtained are set forth in the following Table 1 wherein the percentages have reference to the weight of additive based on the overall composite. In all instances the nickel content was 89-95.5 percent and the aluminum content 4-6 percent. Hardness values were obtained in accordance with standard ASTM Rockwell Hardness procedures. Coating machinability was determined using a tungsten carbide D-shaped tool at turning speeds of 10, 30, 50 and 100 surface feet per minute, and are expressed on a 1 to 11 scale, 1 being the best and 11 the poorest. The cuts were 0.10-0.20 inch with 0.025 inch/reverse traverse, using a soluble oil coolant. The finishes were inspected for burnishing, quality of cutting groove and evidence of particles being torn out.
Table 1 ____________________________________________________________ ______________ MACHINABILITY EVALUATION Run Additive Distance Coating Turning Speed S.F.P.M. Machine 1 Inches Hardness 10 30 50 100 Rating ____________________________________________________________ ______________ 1 2% Ferro-Silicon, 50 Fe/50 Si 6 Rb 56 torn torn torn torn 11 2 2% Ferro-Silicon, 25 Fe/75 Si 6 Rb 54 mod.torn mod.torn torn torn 10 3 2% Ferro-Aluminum, 50 Fe/50 Al 6 Rb 54 burn burn burn torn 7 4 2% Copper, USB118A 6 Rb 54 burn burn torn torn 9 5 2% Titanium Hydride 6 Rb 61 sl. burn sl. burn sl. burn torn 5 6 2% Molybdenum 6 Rb 60 burn sl. burn sl. burn good 2 cutting 2 7 5% Molybdenum 6 Rb 73 burn sl. burn good 2 excell. 2 cutting cutting 1 8 2% El-Chrome, U.C. 4 6 Rb 62 burn good good torn cutting cutting 3 9 5% El-Chrome, U.C. 4 6 Rb 54 burn poor-fair torn torn cutting 8 10 None 5 4 Rb 43 excell. fair 3 torn 3 torn 3 6 cutting cutting 11 None 5 9 Rb 60 fair fair 3 burn 3 torn 3 cutting cutting 4 12 5% Self Fluxing Alloy 6 6 Rb 57 burn burn burn torn 7 ____________________________________________________________ ______________ 1 Rating weighed against turning speed; 1= best 11= poorest. 2 Machine surface was unburnished, very little tool wear. The molybdenum containing alloy appears to lower friction of wearing and cutting surfaces. 3 Excessive tool wear. 4 Electrolytic chromium -400 mesh pounds, 99% chromium. 5 4.5% Al, balance nickel composite powder formed as per example 31, U.S. 3,322,515. 6 -270 mesh +15 micron Cobalt base self fluxing alloy of 27 Ni, 18 Cr, 6 Mo, 3 Si, 3 B, 0.5 max C.
EXAMPLE 2
The process of Example 1 was repeated with various compositions of Ni-Al-Mo, using a ground steel substrate.
In addition a Metco Type "N" powder gun of the type described in U.S. Patent 2,961,335 was used to spray several of the compositions. The "N" gun and its spray conditions are similar to those given for the Type 5P of Example 1, except the acetylene gas flow rate is reduced to 25 cu. ft./hr. The results of the tests are shown in Table 2.
Table 2 ____________________________________________________________ ______________ Composition and Spray Result Summary Run No. Composition Coating Hardness Tensile Bond Remarks wt. % Rb Strength, psi 5P N 5P N ____________________________________________________________ ______________ 13 95.5 Ni 4.5 Al 65 51 4 1- 6650 8080 -- 2- 5580 3160 14 83 Ni 9 Al 8 Mo 72 68 1- 7880 4980 1 Run 14 superior to Run 13 2- 8200 9615 on alpha LFW wear tests 15 86 Ni 9 Al 5 Mo 71 64 1- 6445 5140 -- 2- 4940 5160 16 86 Ni 6 Al 8 Mo 75 -- 5700 4330 -- 17 89 Ni 6 Al 5 Mo 72 -- 5520 -- -- 18 88 Ni 0 Al 12 Mo 68 -- -- -- Bend Test Poor 19 92 Ni 6 Al 2 Mo 66 -- -- -- Bend Test Good 20 95 Ni 3 Al 2 Mo 67 -- -- -- Bend Test Poor-Fair 21 92 Ni 3 Al 5 Mo 69 -- -- -- Bend Test Poor 22 89 Ni 3 Al 8 Mo 73 -- -- -- Bend Test Fair 23 79 Ni 9 Al 12 Mo 70 -- -- -- Bend Test Fair 24 76 Ni 9 Al 15 Mo 77 -- -- -- Bend Test Poor ____________________________________________________________ ______________ 1 Alpha LFW-1 wear tests in both 20 weight oil and kerosene showed 9 Al -- 8 Mo -- 83 N to have lower coefficient of friction than 95.5 Ni-4.5 Al without molybdenum. The Alpha model LFW-1 friction and wear testing machine is manufactured by Dow Corning Corporation and is designed to tes friction and wear characteristics of material under simulated realistic conditions of load and speed.
EXAMPLE 3
By the process of Example 1 there were compared coatings produced by flame spraying a composite of Ni-Al-Mo 83-9-8 and a 95.5-4.5 composite of Ni-Al. The three component composite exhibited superior bond strength, hardness, wear and machinability with resistance to shrinkage, air oxidation and salt water corrosion comparable to those of the control.
In each of these tests two coated specimens were simultaneously run against a cast iron surface submerged in a slurry of 150 grams of Metco 101 alumina abrasive in 500 ml of water. The tests were run for 10 minutes at 235 rpm under a 1400 grams load. The spray conditions and loss ratios are set forth in Table 3.
Table 3 ______________________________________ Material Spray System Weight Thickness Overall and Conditions Average ______________________________________ Metco 5P Gun, 1.19* 1.37* 1.28* P7G Nozzle Ni-Al 6" distance Ni-Al-Mo 30 cfm oxygen 36 cfm acetylene Metco N Gun 0.95** 0.955** 0.953 Ni-Al Standard Ni-Al-Mo conditions for oxygen-acetylene ______________________________________ * average of two runs ** average of eight runs
Various specimens were also tested for bond stength, with the results shown in Table 4.
Table 4 ______________________________________ Bond Strength, PSI 5P Gun 5P Gun N-Gun Coating Thickness: .012-.020" .050" .012-.020 ______________________________________ Material Ni-Al Av. 6040 Av. 2875 Av. 5620 Range Range Range 5170 to 6670 2620 to 3130 2720 to 8400 Ni-Al-Mo Av. 8040 Av. 3830 Av. 7300 Range Range Range 7070 to 8680 3555 to 4105 4750 to 9800 ______________________________________
EXAMPLE 4
The process of Example 1 was repeated with the following changes: the nickel was replaced by copper and the clad composite analyzed 80:12:8 copper:aluminum:molybdenum. For comparison an 80:20 copper:aluminum powder was also prepared and sprayed coatings were made from each. The molybdenum-free coating had a hardness of Rb 50-51 while the molybdenum-containing coating had a hardness of Rb 56-63. The overall machining performance and tool life were also improved.
EXAMPLE 5
9 Parts of finely divided aluminum and 8 parts of finely divided molybdenum were blended with a phenolic varnish having approximately 50 percent solid contents so as to form a mixture having the consistency of a heavy syrup and containing 60 percent by weight of the metals. 100 grams of this varnish-aluminum-molybdenum powder mixture was added to 83 parts metal powders (68:28:4 Ni:Cu:Si and 70:30 Ni-Cu) having a size between -200 and +325 mesh, and the two were thoroughly mixed, with the mixing continued until the varnish dried, leaving a fairly free-flowing powder in which all of the Monel core particles were clad with a dry film, which consisted of aluminum and molybdenum particles bonded to each other and to the core material by the phenolic binder. The powder was then warmed to 250° F. to insure complete drying. There were some minor agglomerates which were screened out and handmilled to reduce the same to a -100 mesh powder. The powder was flame-sprayed on a mild steel plate and gave coatings exhibiting superior qualitative bonding properties and improved coating hardness. Similarly, a molybdenum (8 percent) aluminum (9 percent) clad ferronickel core (64Fe-36Ni) when clad and sprayed under the above conditions exhibited superior qualitative bonding properties and a high hardness of Rb 83.
EXAMPLE 6
A composite wire can be formed by winding individual wires of nickel, aluminum and molybdenum to form a stranded wire of 0.125 inch comprising 83:9:8 Ni:Al:Mo. The wire can be sprayed using a Metco type 10E spray gun with acetylene at a pressure of 15 p.s.i. and a flow rate of 37 cu. ft./hr. with oxygen as the oxidizing gas at a pressure of 38 p.s.i. and a flow rate of 75 cu. ft./hr. Air is used as a blast gas at a pressure of 55 p.s.i. and a flow rate of 30 cu. ft./min.
EXAMPLE 7
An aluminum tube 0.375 inch in outside diameter can be filled with a mixture of nickel powder and molybdenum powder to result in a structure comprising 83:9:8 Ni:Al:Mo. The tube ends are welded closed and 3/8 inch diameter feed stock is then swaged to 1/4 inch diameter, then to a 3/16 inch diameter then to a 1/8 inch finished wire diameter. The wire is then annealed and coiled. The wire is then sprayed, using the conventional wire type flame spray gun sold by Metco Inc. as the Metco type 10E gun. Spraying is effected, using acetylene at a pressure of about 15 lbs. p.s.i. and a flow rate of 37 cu. ft./hr. and oxygen as the oxidizing gas at a pressure of 38 lbs. p.s.i. and flow rate of 75 cu. ft./hr. Air is used as a blast gas at a pressure of 55 lbs. p.s.i. and flow rate of 30 cu. ft./min. The wire is sprayed at a rate of 5 ft. per minute. The spray material is deposited on a surface of ground and machine-finished, cold rolled steel.
It will be appreciated that the instant specification and examples are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention.
It is common to line metal surfaces with other metals of different mechanically superior properties to obtain the best properties of both metals, e.g. cylinders in aluminum engine blocks have been lined with iron sheets to give the benefits of the light weight of aluminum and the wear properties of iron. An improvement thereon involved flame spraying the wear surface onto the receiving surface. To ensure a secure bond between substrate and sprayed metal it was customary to prepare the substrate by mechanical roughening. U.S. Pat. Nos. 2,588,421 and 2,588,422 made a further improvement thereon in that molybdenum was first flame sprayed onto the substrate without need for special preparation of the substrate. Thereafter a hard wear surface such as high carbon steel could be sprayed and the laminate would be securely held together.
For certain purposes it was desired that the flame sprayed surface constitute an intermetallic compound. In U.S. Pat. No. 3,322,515 there is described a flame spray composite material whose components exothermically interact with one another when melted so as to form such intermetallic compound which is deposited upon the substrate. The heat generated by the exothermic reaction aids in the bonding. The composite may comprise separate strands of the two components, e.g. a strand of nickel and a strand of aluminum, the strands being simultaneously fed to a flame spray gun. In accordance with a preferred technique one of the components can be coated onto the other, e.g. a wire comprising a nickel core and an aluminum sheath.
These composites functioned in generally satisfactory fashion but had certain significant limitations. One was that spraying of the nickel aluminum composites produced a great deal of smoke, requiring special ventilating measures. This was solved in U.S. Pat. No. 3,338,688 by employing nickel boron along with aluminum as the coating on the nickel core.
There is still one significant requirement which such composites impose where the coated substrate must undergo further mechanical working. Specifically, whether the self-bonded coating was molybdenum or nickel-aluminum, the surface did not have good machinability. Molybdenum is too hard and requires grinding rather than simple machining; grinding is far more expensive with respect to both equipment and labor. Nickel-aluminum produces rapid tool wear and a rough finish, which problems are not overcome even by varying the nickel and aluminum proportions.
It is accordingly an object of the present invention to provide flame sprayable compositions which are self-bonding and which produce coatings which may readily be worked without de-bonding.
A further object of the invention is to produce superior flame sprayed bearing surfaces.
These and other objects and advantages are realized in accordance with the present invention pursuant to which there is provided a self-bonding composite of exothermically interacting metal components comprising aluminum, molybdenum and at least one metal selected from the group consisting of nickel, copper and iron. The resulting coatings are characterized by excellent bonding and superior bearing and wearing surfaces. They can readily be worked either by grinding or machining.
The novel self-bonding clad material may comprise about 66 to 97.5 percent and preferably about 73 to 89 percent by weight of nickel, copper and/or iron. The aluminum may comprise about 2 to 18 percent and preferably about 5 to 15 percent by weight of the total composition. The molybdenum may comprise about 0.5 to 16 percent and preferably about 6 to 12 percent by weight.
The nickel, copper or iron may be present as such or as an alloy with one another optionally containing a minor amount of other ingredients, e.g. up to about 10 or even 20 percent or more by weight of substances such as silicon, boron, chromium, cobalt, etc. The nickel-copper-iron component preferably constitutes a core which is clad with the aluminum and molybdenum. When used in clad-powder form, the composite of aluminum and molybdenum coated nickel-copper-iron particles should have the general overall shape and size of conventional flame spray powders.
The initial nickel-copper-iron particles which constitute the core or nucleus of the composite powders in accordance with the invention should have a size and shape approximating that desired in the end powders as described above. The nickel-copper-iron core or nucleus particles are then coated with the aluminum and molybdenum, the coating being effected by any known coating process, as for example described in U.S. Pat. No. 3,322,515.
Preferably the aluminum and the molybdenum are deposited in finely divided form in a binder on the nickel-copper particles.
The aluminum and molybdenum preferably in as finely divided form as possible, as for example a size of -325 mesh, are mixed in the required proportions with a binder or lacquer so as, in effect, to form a paint in which the aluminum and molybdenum particles correspond to the pigment. The paint is then used to coat the nickel core particles and allowed to set or dry.
The binder material may be any known or conventional binder material which may be used for forming a coating or for bonding particles together or to a surface. The binder is preferably a varnish containing a resin as the varnish solids, and may contain a resin which does not depend on solvent evaporation in order to form a dried or set film. The varnish may thus contain a catalyzed resin as the varnish solids. Examples of binders which may be used include the conventional phenolic epoxy or alkyd varnishes, varnishes containing drying oils, such as tuna oil and linseed oil, rubber and latex binders and the like.
The coating of the nickel-copper-iron core component with the "paint" containing the aluminum and molybdenum may be effected in any known or desired manner, and it is simply necessary to mix the two materials together and allow the binder to set or dry which will result in a fairly free-flowing powder consisting of the nickel-copper-iron core coated with cladding of the aluminum and molybdenum.
The molybdenum powder may be any known powder including molybdenum alloys containing more than 50 percent molybdenum and most preferably is used in a particle size range between -20 and +1 micron.
The powders are sprayed in the conventional manner, using a powder type flame spray gun, though it is also possible to combine the same in the form of a wire or rod, using plastic or a similar binding, as for example polyethylene which decomposes in a heating zone of the gun. When formed as wires, the same may have conventional sizes and accuracy tolerances for flame spray wires and thus, for example, may vary in size between 1/4 inch and 20 gauge.
The spraying is in all respects effected in the conventional manner previously utilized for self-bonding flame spray material, and in particular nickel aluminum composites. Due to the self-bonding characteristics, special surface preparation other than a good cleaning is not required though, of course, conventional surface preparation may be utilized if desired. The powder in accordance with the invention may be flame-sprayed as a bonding coat for subsequently applied flame spray material or any purposes where it is desired to form the nickel-copper aluminide coating containing molybdenum. The composites may furthermore be sprayed in conjunction with, or in addition to, other flame spray materials conventionally used in the art.
When sprayed, the nickel, copper and/or iron and aluminum exothermically react, forming a nickel, copper and/or iron aluminide intermetallic. The molybdenum and aluminum also exothermically react, forming molybdenum aluminide intermetallic. Complex nickel- copper- and/or iron-molybdenum aluminides and alloys may be formed.
The term "composite" as used herein is intended to designate a structurally integral unit and does not include a mere mixture of components which may be physically separated without any destruction of the structure. Thus, in the case of powder, the term "composite" does not include a simple mixture of individual granules of the separate components, but requires that each of the individual granules contain the separate components which will exothermically react, forming intermetallic compounds. In the case of wire, the individual components must be incorporated in a single wire. In the composite the components must be in intimate contact with each other.
In connection with powders, each grain may consist of an aggregate containing the components which will exothermically react, forming the intermetallic compound, but preferably the individual grains of the powder are in the form of a clad composite consisting of a nucleus of one of the components and at least one coating layer of the other components. Alternatively, the composite may consist of separate, concentric coating layers of at least two of the components and a nucleus of the third or even a fourth material.
In the case of wires, the composites may be in the form of a wire having a coating sheath of one material and a core of the others, alternate coating sheaths of two of the components and a core of the third or a fourth material, a wire formed by twisting or rolling separate wire strands of the components, a wire consisting of a sheath of one component and a core containg the other components in powder or compacted form, a wire consisting of a sheath of one component and a core containing a compacted powder mixture of this same component material and other components, a wire consisting of a plastic sheath and a core containing a compacted powder mixture of components, etc.
In order for the wires to be satisfactory for spraying, the same must not cavitate at the tip when heated, and should preferably be capable of forming a pointed or slightly tapered tip when being melted and sprayed. Thus, if the wires have an outer layer or sheath of one component and an inner core of another component, the inner core cannot have a lower melting point that the outer sheath, as otherwise the inner core will initially melt, causing cavitation at the tip. For example, if the wire is in the form of a core with a coating sheath, the coating sheath must be aluminum, as otherwise during the spraying operation the wire will initially melt out, causing the cavitation which will interfere with a satisfactory spraying operation. The wire having the melting-point characteristics so as to allow the melting off of the tip without this cavitation is referred to herein and in the claims as "non-cavitating wire."
While the components may be present in the stoichiometric proportions required for the formation of the intermetallic compound, it is, however, possible to also have an excess of one or the other provided the relative amounts are sufficient to release quantities of heat in the formation of the intermetallic compounds.
The clad powders, in accordance with the invention, may be formed in any known or desired manner, including known chemical plating processes, in which coating material is deposited on a seed or nucleus of another material, or in which multiple layers of various materials are built up on the seed material, or in which various materials are co-deposited in a single layer on the seed material.
A mode of forming the clad powders involves the depositing of a metal from a solution by reduction on a seed or nucleus, such as by the hydrogen reduction of ammoniacal solutions of nickel and/or copper and ammonium sulfate on a seed powder catalyzed such as by the addition of anthraquinone. It is also possible to form the coating by other processes, such as coating by vapor deposition, by the thermal decomposition of metal carbonyls, by hydrogen reduction of metal halide vapors, by thermal deposition of halides, hydrides, carbonyls, organometals, or other volatile compounds, or by displacement gas plating and the like.
A preferred and greatly simplified mode of forming the clad powders in accordance with the invention is the depositing of two components as coating in the form of a paint on the third component. Thus two of the components which are to form the coating or cladding, may be dispersed in finely divided form in a binder or lacquer so as, in effect, to form a paint in which this component corresponds to the pigment. The paint is then used to coat core particles of the third component and the binder or lacquer allowed to set or dry. The binder material is preferably a resin which does not depend on solvent evaporation in order to form a dried or set film, and which film will decompose or break down in the heat of the spraying process. The binder, for example, may be a phenolic varnish or any other known or conventional varnish, preferably containing a resin as the varnish solids. The components which are initially mixed with the binder or varnish should preferably be as finely divided as possible, as for example -325 mesh. The other component which constitutes the core should be approximately or only slightly below the particle size ultimately desired for the spray powder. The coating of the core component with the "paint" may be effected in any known or desired manner, and it is simply necessary to mix the two materials together and allow the binder to dry or set, which will result in a fairly free-flowing powder consisting of the core component coated with a cladding of the other component bound in the binder.
The aggregates may be formed by compacting or briquetting the various components into the individual granules, or into larger aggregates and then breaking these aggregates into the granules.
The wires may be formed in the known conventional manner for forming wires with various components as, for example, by shrinking a sheath on a core, by forming the core with powder, by twisting the component wires, followed by rolling, drawing, swaging, or the like if desired.
In accordance with one mode of manufacture, one of the components may be formed into a tube or sheath and filled with a powder of the other components or a powder comprising a mixture of the three components, or containing additional components. The tube ends are then sealed and the wire reduced to the desired wire diameter by swaging, rolling or drawing. Preferably the powder or powder mixture is first compressed into cylindrical briquettes before being placed in the sheath or core. The sealing of the tube ends after loading with the powder or powder mixture can be effected, for instance, by insertion of a plug, for example of the metal of the sheath, by welding, twisting, crimping, or the like.
Powders in accordance with the invention should have the general over-all shape and size of conventional, flame spray powders, and thus for example should have a size between -60 mesh and +3 microns and preferably -140 mesh and +10 microns (U.S. Standard screen mesh size). Most preferably the powder should be as uniform as possible in grain size, with the individual grains not varying by more than 250 microns and preferably 75 microns.
Depending on the particular flame spray process and the desired purpose, the composite powder may be sprayed per se or in combination with other different composite powders, or in combination with other conventional flame spray powders or powder components.
While the powders are preferably sprayed, as such, in a powder type of flame spray gun, it is also possible to combine the same in the form of a wire or rod, using a plastic or similar binder, which decomposes in the heating zone of the gun, or in certain cases the powders may be compacted and/or sintered together in the form of a rod or wire. The wires must have the conventional sizes and accuracy tolerances for flame spray wires and thus for example may vary in size between 1/4 inch and 20 gauge, and are preferably of the following sizes: 3/16 + 0.0005 inch to -0.0025 inch, 1/8 + 0.0005 inch to -0.0025 inch, 11 gauge + 0.0005 inch to -0.0025 inch, and 15 gauge + 0.0001 inch, with a smooth clean finish free from surface marks, blemishes, or defects. The wires are sprayed in the conventional manner, using conventional wire-type flame spray guns.
In combining, in the exothermic reaction, forming the intermetallic compound, the components generate heat in situ in the actual material which is to form at least a part of the coating. This is to be distinguished from flame-spray processes and materials in which heat is generated by a reaction, such as an oxidation reaction in which a foreign and non-metallic element is introduced and in which undesirable components may be produced. Aside from greatly contributing to the thermal efficiency of the process, the heat generated in situ in the formation of the intermetallic compound produces novel results, in many instances forming a denser, more adhering coating, having characteristics of at least a partially fused coating. In many instances the coating has self-bonding characteristics, so that special surface preparation, other than a good cleaning, is not required. The spraying in all other respects is effected in the conventional, well-known manner, using conventional flame spray equipment, and the conventional surface preparation may be utilized, if desired. The composites in accordance with the invention may be sprayed in conjunction with or in addition to other flame spray materials conventionally used in the art, or may be sprayed in combination or conjunction with the others.
The use of the nickel-, copper- and/or iron-aluminum-molybdenum composites, will generally improve the bond of the total sprayed material, and thus of the other component or components to the substrate, sometimes making the mixture self-bonding. The particle bond will be improved and the coating will be denser, so that its porosity may be decreased. In general, as little as about 5 percent by weight of the composites in accordance with the invention will be sufficient to substantially improve the bonding characteristics and decrease the porosity of other flame spray materials, such as conventional flame spray metals, alloys or ceramics. There is, of course, no upper limit on the amount as the composite may be sprayed per se, but generally at least about 20 percent by weight of the other component is required if this component is to have a pronounced effect on the characteristics of the coating. Thus, the novel composite when blended may constitute about 5 to 80 percent by weight of the blend, advantageously about 10 to 50 percent and preferably about 10 to 20 percent.
Representative materials with which the novel composites may be flame sprayed include self-fluxing metal powders as described in U.S. Pat. Nos. 2,875,043, 2,936,224 and 3,305,326 as well as carbides as described in U.S. Pat. No. 3,305,326 and mixtures thereof. Preferably the self-fluxing, spray-weld powders are of the nickel or cobalt type, containing boron and most preferably boron and silicon, as the self-fluxing element. The most preferable spray-weldable, self-fluxing metal powders are of the nickel or nickel-chromium alloy type containing boron and silicon. In addition to the base metal, i.e. the nickel and/or cobalt, and the fluxing element, which is the boron or boron and silicon, the powder may be formed of additional alloy components, as for example up to 20 percent chromium, to impart corrosion and oxidation-resistance, carbon in the amount of not more than a few percent, iron in an amount not exceeding about 10 percent and preferably 5 percent by weight of the total alloy. A typical spray-weldable alloy of the boron nickel type of which the powder is composed may, for example, consist of 0.7 to 1 percent carbon, 3.4 to 4.5 percent silicon, 2.75 to 3.75 percent boron, 3-5 percent iron, up to 18 percent chromium, as for example 16 to 18 percent chromium, with nickel making up the balance.
A typical spray-weld alloy of the cobalt-base type may, for example, contain from 1.5 to 3 percent boron, 0 to 4.5 percent silicon, 0 to 3 percent carbon, 0 to 20 percent chromium, 0 to 30 percent nickel, 0 to 20 percent molybdenum, 0 to 20 percent tungsten, and the balance cobalt.
When the novel composites, optionally blended with a self fluxing metal powder, are further blended with a refractory carbide, such as tungsten carbide, titanium carbide, zirconium carbide, tantalum carbide, columbium carbide, hafnium carbide, chromium carbide or the like, extremely high quality coatings are produced, which are superior in various respects to the conventional carbide coatings.
The carbides used in accordance with this embodiment should have a particle size between about -140 mesh U.S. Standard screen size and 8 microns, and preferably between about -270 mesh and + 15 microns, with the amount of carbide being between about 10-75 percent and preferably 45-55 percent by weight, based on the total powder mixture.
If the refractory carbide powder is in a form so that the refractory carbide is bound in a matrix, as for example a cobalt or nickel matrix containing 5-20 percent by weight of either cobalt or nickel, unusually hard and wear-resistant coatings will be produced which do not contain the individual carbide particles imbedded in a fused matrix, but instead contain alloy phases whose micro-hardness is actually substantially higher than that ordinarily obtained from a bonded carbide.
When the powder, in accordance with the invention, containing this matrix-bonded refractory carbide is plasma-sprayed, the same is self-bonding, so that the conventional surface preparation for flame spraying, as for example a deep surface roughening, is not required.
The carbide coatings formed in accordance with the above are extremely hard and wear-resistant, and may be useful as bearing surfaces, abrasive surfaces, and for any other purpose wherein a working surface requires extremely wear-resistant coating.
The refractory carbide, need not be matrix-bound, but should be a pure crystalline carbide, also having the particle size and used in the amounts indicated above. The crystalline carbide-containing coatings formed in accordance with the invention will have extremely high wear-resistance due to the carbide particles, which are dispersed and tightly bound in the fused coating. Coatings may be used for the same type of applications as mentioned in connection with the coatings formed with the matrix-bound carbide.
The following examples, wherein all parts are by weight unless otherwise expressed, are given by way of illustration and not limitation.
EXAMPLE 1
Finely divided aluminum powder (-325 mesh) was dry blended with different selected powders (-400 mesh) in varying amounts. The powder blend was then admixed with a conventional phenolic varnish having approximately 10 percent solid contents so as to form a mixture having the consistency of heavy syrup and containing about 60 percent by weight of the metal particles. 100 grams of the varnish powder mixture was then added to about 900 grams of nickel powder having a size between about 200-325 mesh and the two were thoroughly mixed, with the mixing continued until the varnish dried, leaving a fairly free-flowing powder in which all of the nickel core particles were clad with a dry film which contained the aluminum particles and other selected particles. The powder was then warmed to about 250°F. to ensure complete drying. The powder was then screened and hand-milled to reduce the same to a -100 mesh powder. The powder was flame-sprayed on a mild steel plate which had been surface cleaned by smooth grinding. The spraying was effected at a distance of 6 inches from the plate, using a powder type flame spray gun as described in U.S. Pat. No. 2,961,335 of Nov. 22, 1960 and sold by Metco, Inc., of Westbury, N.Y., under the trade name "Thermospray" powder gun, Type 5 P. The spraying was effected at a rate of 5 to 10 lbs. of powder per hour, using acetylene gas as the fuel, at a pressure of 11 lbs. p.s.i. gauge and a flow rate of 36 cu. ft./hr., and oxygen as the oxidizing gas at a pressure of 15 lbs. p.s.i. gauge and a flow rate of 30 cu. ft./hr. During the spraying a coating layer was built up to a thickness of between 0.030 and 0.050 inch.
The results obtained are set forth in the following Table 1 wherein the percentages have reference to the weight of additive based on the overall composite. In all instances the nickel content was 89-95.5 percent and the aluminum content 4-6 percent. Hardness values were obtained in accordance with standard ASTM Rockwell Hardness procedures. Coating machinability was determined using a tungsten carbide D-shaped tool at turning speeds of 10, 30, 50 and 100 surface feet per minute, and are expressed on a 1 to 11 scale, 1 being the best and 11 the poorest. The cuts were 0.10-0.20 inch with 0.025 inch/reverse traverse, using a soluble oil coolant. The finishes were inspected for burnishing, quality of cutting groove and evidence of particles being torn out.
Table 1 ____________________________________________________________ ______________ MACHINABILITY EVALUATION Run Additive Distance Coating Turning Speed S.F.P.M. Machine 1 Inches Hardness 10 30 50 100 Rating ____________________________________________________________ ______________ 1 2% Ferro-Silicon, 50 Fe/50 Si 6 Rb 56 torn torn torn torn 11 2 2% Ferro-Silicon, 25 Fe/75 Si 6 Rb 54 mod.torn mod.torn torn torn 10 3 2% Ferro-Aluminum, 50 Fe/50 Al 6 Rb 54 burn burn burn torn 7 4 2% Copper, USB118A 6 Rb 54 burn burn torn torn 9 5 2% Titanium Hydride 6 Rb 61 sl. burn sl. burn sl. burn torn 5 6 2% Molybdenum 6 Rb 60 burn sl. burn sl. burn good 2 cutting 2 7 5% Molybdenum 6 Rb 73 burn sl. burn good 2 excell. 2 cutting cutting 1 8 2% El-Chrome, U.C. 4 6 Rb 62 burn good good torn cutting cutting 3 9 5% El-Chrome, U.C. 4 6 Rb 54 burn poor-fair torn torn cutting 8 10 None 5 4 Rb 43 excell. fair 3 torn 3 torn 3 6 cutting cutting 11 None 5 9 Rb 60 fair fair 3 burn 3 torn 3 cutting cutting 4 12 5% Self Fluxing Alloy 6 6 Rb 57 burn burn burn torn 7 ____________________________________________________________ ______________ 1 Rating weighed against turning speed; 1= best 11= poorest. 2 Machine surface was unburnished, very little tool wear. The molybdenum containing alloy appears to lower friction of wearing and cutting surfaces. 3 Excessive tool wear. 4 Electrolytic chromium -400 mesh pounds, 99% chromium. 5 4.5% Al, balance nickel composite powder formed as per example 31, U.S. 3,322,515. 6 -270 mesh +15 micron Cobalt base self fluxing alloy of 27 Ni, 18 Cr, 6 Mo, 3 Si, 3 B, 0.5 max C.
EXAMPLE 2
The process of Example 1 was repeated with various compositions of Ni-Al-Mo, using a ground steel substrate.
In addition a Metco Type "N" powder gun of the type described in U.S. Patent 2,961,335 was used to spray several of the compositions. The "N" gun and its spray conditions are similar to those given for the Type 5P of Example 1, except the acetylene gas flow rate is reduced to 25 cu. ft./hr. The results of the tests are shown in Table 2.
Table 2 ____________________________________________________________ ______________ Composition and Spray Result Summary Run No. Composition Coating Hardness Tensile Bond Remarks wt. % Rb Strength, psi 5P N 5P N ____________________________________________________________ ______________ 13 95.5 Ni 4.5 Al 65 51 4 1- 6650 8080 -- 2- 5580 3160 14 83 Ni 9 Al 8 Mo 72 68 1- 7880 4980 1 Run 14 superior to Run 13 2- 8200 9615 on alpha LFW wear tests 15 86 Ni 9 Al 5 Mo 71 64 1- 6445 5140 -- 2- 4940 5160 16 86 Ni 6 Al 8 Mo 75 -- 5700 4330 -- 17 89 Ni 6 Al 5 Mo 72 -- 5520 -- -- 18 88 Ni 0 Al 12 Mo 68 -- -- -- Bend Test Poor 19 92 Ni 6 Al 2 Mo 66 -- -- -- Bend Test Good 20 95 Ni 3 Al 2 Mo 67 -- -- -- Bend Test Poor-Fair 21 92 Ni 3 Al 5 Mo 69 -- -- -- Bend Test Poor 22 89 Ni 3 Al 8 Mo 73 -- -- -- Bend Test Fair 23 79 Ni 9 Al 12 Mo 70 -- -- -- Bend Test Fair 24 76 Ni 9 Al 15 Mo 77 -- -- -- Bend Test Poor ____________________________________________________________ ______________ 1 Alpha LFW-1 wear tests in both 20 weight oil and kerosene showed 9 Al -- 8 Mo -- 83 N to have lower coefficient of friction than 95.5 Ni-4.5 Al without molybdenum. The Alpha model LFW-1 friction and wear testing machine is manufactured by Dow Corning Corporation and is designed to tes friction and wear characteristics of material under simulated realistic conditions of load and speed.
EXAMPLE 3
By the process of Example 1 there were compared coatings produced by flame spraying a composite of Ni-Al-Mo 83-9-8 and a 95.5-4.5 composite of Ni-Al. The three component composite exhibited superior bond strength, hardness, wear and machinability with resistance to shrinkage, air oxidation and salt water corrosion comparable to those of the control.
In each of these tests two coated specimens were simultaneously run against a cast iron surface submerged in a slurry of 150 grams of Metco 101 alumina abrasive in 500 ml of water. The tests were run for 10 minutes at 235 rpm under a 1400 grams load. The spray conditions and loss ratios are set forth in Table 3.
Table 3 ______________________________________ Material Spray System Weight Thickness Overall and Conditions Average ______________________________________ Metco 5P Gun, 1.19* 1.37* 1.28* P7G Nozzle Ni-Al 6" distance Ni-Al-Mo 30 cfm oxygen 36 cfm acetylene Metco N Gun 0.95** 0.955** 0.953 Ni-Al Standard Ni-Al-Mo conditions for oxygen-acetylene ______________________________________ * average of two runs ** average of eight runs
Various specimens were also tested for bond stength, with the results shown in Table 4.
Table 4 ______________________________________ Bond Strength, PSI 5P Gun 5P Gun N-Gun Coating Thickness: .012-.020" .050" .012-.020 ______________________________________ Material Ni-Al Av. 6040 Av. 2875 Av. 5620 Range Range Range 5170 to 6670 2620 to 3130 2720 to 8400 Ni-Al-Mo Av. 8040 Av. 3830 Av. 7300 Range Range Range 7070 to 8680 3555 to 4105 4750 to 9800 ______________________________________
EXAMPLE 4
The process of Example 1 was repeated with the following changes: the nickel was replaced by copper and the clad composite analyzed 80:12:8 copper:aluminum:molybdenum. For comparison an 80:20 copper:aluminum powder was also prepared and sprayed coatings were made from each. The molybdenum-free coating had a hardness of Rb 50-51 while the molybdenum-containing coating had a hardness of Rb 56-63. The overall machining performance and tool life were also improved.
EXAMPLE 5
9 Parts of finely divided aluminum and 8 parts of finely divided molybdenum were blended with a phenolic varnish having approximately 50 percent solid contents so as to form a mixture having the consistency of a heavy syrup and containing 60 percent by weight of the metals. 100 grams of this varnish-aluminum-molybdenum powder mixture was added to 83 parts metal powders (68:28:4 Ni:Cu:Si and 70:30 Ni-Cu) having a size between -200 and +325 mesh, and the two were thoroughly mixed, with the mixing continued until the varnish dried, leaving a fairly free-flowing powder in which all of the Monel core particles were clad with a dry film, which consisted of aluminum and molybdenum particles bonded to each other and to the core material by the phenolic binder. The powder was then warmed to 250° F. to insure complete drying. There were some minor agglomerates which were screened out and handmilled to reduce the same to a -100 mesh powder. The powder was flame-sprayed on a mild steel plate and gave coatings exhibiting superior qualitative bonding properties and improved coating hardness. Similarly, a molybdenum (8 percent) aluminum (9 percent) clad ferronickel core (64Fe-36Ni) when clad and sprayed under the above conditions exhibited superior qualitative bonding properties and a high hardness of Rb 83.
EXAMPLE 6
A composite wire can be formed by winding individual wires of nickel, aluminum and molybdenum to form a stranded wire of 0.125 inch comprising 83:9:8 Ni:Al:Mo. The wire can be sprayed using a Metco type 10E spray gun with acetylene at a pressure of 15 p.s.i. and a flow rate of 37 cu. ft./hr. with oxygen as the oxidizing gas at a pressure of 38 p.s.i. and a flow rate of 75 cu. ft./hr. Air is used as a blast gas at a pressure of 55 p.s.i. and a flow rate of 30 cu. ft./min.
EXAMPLE 7
An aluminum tube 0.375 inch in outside diameter can be filled with a mixture of nickel powder and molybdenum powder to result in a structure comprising 83:9:8 Ni:Al:Mo. The tube ends are welded closed and 3/8 inch diameter feed stock is then swaged to 1/4 inch diameter, then to a 3/16 inch diameter then to a 1/8 inch finished wire diameter. The wire is then annealed and coiled. The wire is then sprayed, using the conventional wire type flame spray gun sold by Metco Inc. as the Metco type 10E gun. Spraying is effected, using acetylene at a pressure of about 15 lbs. p.s.i. and a flow rate of 37 cu. ft./hr. and oxygen as the oxidizing gas at a pressure of 38 lbs. p.s.i. and flow rate of 75 cu. ft./hr. Air is used as a blast gas at a pressure of 55 lbs. p.s.i. and flow rate of 30 cu. ft./min. The wire is sprayed at a rate of 5 ft. per minute. The spray material is deposited on a surface of ground and machine-finished, cold rolled steel.
It will be appreciated that the instant specification and examples are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention.