TUNGSTEN CARBIDE COBALT CHIP MATRIX, BEARING MATERIAL

Abstract: A bearing composition which contains tungsten carbide powder and cemented tungsten carbide cobalt chips is bonded to a steel blank to form a bearing surface. The tungsten carbide powder is blended with the tungsten carbide cobalt chips and loaded into a cavity (15) surrounding the steel blank and is subsequently infiltrated with a copper based infiltrant (18) to form a chip matrix bearing surface.

Description: v Tungsten Carbide Cobalt Chip Matrix, Bearing Material . BACKGROUND OF THE D ISC LOS URE 1 . Field of the Invention 5 The subject invention pertains to metal bearings, and more particularly to bearings employing tungsten carbide surfaces. 2. Description of Related Art 10 In the prior art, bearing surfaces employing tungsten carbide have been manufactured by molding tungsten carbide buttons to a steel radial bearing sleeve utilizing a fine tungsten carbide powder and copper base infiltrant. The buttons are affixed to the surface of 15 the carbon mold in a predetermined pattern which, depending upon size, may utilize as many as 299 buttons. Once molded into place, the buttons are surrounding matrix must be machined finished. The process of setting the buttons is relatively 20 labor intensive. In addition, the tungsten carbide buttons are more expensive than tungsten carbide chip material. Therefore, it has appeared to the inventors that an improved and less expensive bearing surface might be constructed from available tungsten carbide chip 25 material. SUMMARY OF NOVEL ASPECTS OF THE DISCLOSURE It is therefore an object of the invention to provide an improved bearing structure. It is another object of the invention to provide a less expensive process of manufacturing a bearing surface employing tungsten carbide material. It is another object of the invention to eliminate the expense involved in setting tungsten carbide buttons in prior art. bearing structures. It is still another object of the invention to provide a tungsten carbide bearing structure and process which is less expensive than those of the prior art. In accordance with the invention, a chip matrix is created from a mixture of macro-crystalline tungsten carbide powder and cemented tungsten carbide cobalt chips. The blend is such that the mixture of powders may be loaded in a cavity surrounding a steel blank and infiltrated with a copper base infiltrant and cooled to provide a bearing surface ready for finishing. The resultant chip matrix may be molded closer to final size, therefore requiring less time to finish compared to the prior art button structure. An additional advantage is that the percentage of tungsten carbide bearing surface area is increased over the molded button approach. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart illustrating the process of manufacturing a bearing surface according to the preferred embodiment; FIG. 2 illustrates a graphite molded steel blank utilized according to the preferred embodiment; and FIG. 3 illustrates a graphite mold and steel blank also used according to the preferred embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT According to the process illustrated in FIG. 1, macro-crystalline tungsten carbide powder is blended together with cemented tungsten carbide cobalt chips. 5 This mixture is preferably comprised of sixty percent (60%) by weight of 80 mesh and down macro-crystalline tungsten carbide, commercially available as the Kenametal product designated P-90. The range of particle sizes, i.e., 80 mesh and down, is selected for optimum- packing J_ Q density of the mixture. The other component of the mixture is forty percent (40%) by weight of cemented tungsten carbide cobalt chips, for example TCM 10/18 mesh crushed WC-Co C grade. A suggested range for the percentage of weight of 5 tungsten carbide cobalt chips from forty to eighty percent (40-80%) , with the preferred percentage being sixty percent (60%) . To create a bearing surface, a steel blank is first machined (step 11) and then surrounded by a 2o graphite mold (step 13). The blended mixture is loaded into a cavity 21 (e.g., FIG. 2) created between the steel blank and graphite mold, step 15. The mold contents are then vibrated, step 17, for maximum density of the blended mixture. Copper infiltrant nuggets are then 25 inserted in the mold at step 18. The mold contents are then heated to 2050 degrees Fahrenheit (F), plus or minus 25 degrees F, for example by induction heating, step 19. The heated powder mixture in the cavity 21 is infiltrated through capillary 30 action with copper base infiltrant, step 19 and slow cooled to room temperature. After cooling, the parts are machined to specific dimensions by grinding, step 20. FIG. 2 illustrates a particular set-up for use in the subject process for applying a bearing surface to the outer surface of a cylindrical steel bearing blank 23. The apparatus includes a mold body 31, a mold cap 33 and a mold plug 35. The mold body 31 rests in a mold base 37 and is separated from the bearing blank 23 by graphite fiber 39. Graphite fiber 41 also lines the inner wall of the mold body 31. The infiltrant 27 is separated by a layer of tungsten powder 42 from the 1 Q cavity 21 which contains the blended mixture of tungsten carbide powder and cemented tungsten carbide cobalt chips. The tungsten powder when infiltrated facilitates machining of the end of the sleeve. FIG. 3 illustrates mold apparatus similar to ^ FIG. 2 for applying a bearing surface to the inner surface of a cylindical steel bearing blank 43. The mold apparatus includes a mold body 45 and a mold base 46 which surrounds the blank 43. A graphite belt ring 44 is attached by double-sided adhesive tape to the lower end 2o °f the blank 43. A funnel 52 rests upon the top of the mold body 45. A core 47 is positioned within the bearing blank 43 to create a cavity 48 for the blended mixture of tungsten carbide power and cemented tungsten carbide chips. Again, a layer of tungsten 25 powder 49 is used to separate the infiltrant nuggets 51 from the cavity 48. As will be apparent to those skilled in the art, the subject invention admits of numerous adaptations and modi ications without departing from the scope and spirit 30 of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.

Claims: CLAIMS What is Claimed Is: 1. A bearing structure comprising: a steel blank surface; a bearing surface comprising of a blend of macro-crystalline tungsten carbide powder and c cemented tungsten carbide cobalt chips together with a copper base infiltrant. 2. A composition for fabricating bearings comprising: macro—crystalline tungsten carbide powder; and 5 cemented tungsten carbide cobalt chips. 3. The composition of claim 2 wherein the composition is comprised of sixty percent (60%) by weight of macro-crystalline tungsten carbide powder and forty percent (40%) by weight of cemented tungsten carbide 5 chips. 4. The composition of claim 2 wherein the cemented tungsten carbide chips comprise from forty to eight percent (40-80%) by weight of said composition. 5. The composition of claim 2 wherein said macro-crystalline tungsten carbide is a mixture of macro-crystalline tungsten carbide particles with size optimized for packing. 6. The composition of claim 2 wherein the macro-crystalline tungsten carbide powder is a mixture of 80 mesh and down particle sizes. 7. A process of bearing manufacture comprising the steps of: blending together a mixture of macro-crystalline tungsten carbide particles and cemented tungsten carbide cobalt chips; positioning a layer of said mixture adjacent to a blank metal surface; adding tungsten powder vibrating the mixture; loading a copper base infiltrant heating the mixture; infiltrating the heated mixture with copper base infiltrant; and cooling the mixture. 8. The process of claim 7 wherein the blank is fabricated of steel. 9. The process of claim 7 wherein the mixture comprises about forty percent (40%) by weight of cemented tungsten carbide cobalt chips and sixty percent (60%) by weight of macro-crystalline carbide powder. 10. The process of claim 7 wherein the mixture of macro-cry3talline tungsten carbide powder is optimized for packing. 11. The process of claim 7 wherein the macro-crystalline tungsten carbide comprises a mixture of 80 mesh and down macro-crystalline tungsten carbide particles. 12. The process of claim 7 wherein the step of heating comprises heating the vibrated mixture to a temperature of about 2050 degrees fahrenheit.

Inventors: GECZY BELA, TOTH ROBERT G, GECZY, BELA, TOTH, ROBERT, G.
Applicants: SMITH INTERNATIONAL, SMITH INTERNATIONAL, INC.
Application year: 1986
Main classification: C22C29
IPC codes: B22F7, C22C29, F16C33