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Title: Process for the preparation of a composite cubic boron nitride layer abrasive body
Claims: What I claim as new and desire to secure by Letters Patent of the United States is: 1. A process for the preparation of a composite abrasive body comprising the steps of: a. placing within a protective metal container (1) a layer of a mass of clean cubic boron nitride crystals, (2) a layer of bonding alloy or metal for providing said bonding alloy for infusing and wetting the clean surfaces of capillary-size voids in said mass of cubic boron nitride crystals, said bonding alloy being a metal alloy having a critical wetting temperature of less than about 1500.degree.C, being capable of reducing B.sub.2 O.sub.3 and exhibiting a limited finite reactivity with cubic boron nitride, the amount of said bonding alloy ranging from about 30 to 60% by volume of said mass of cubic boron nitride crystals, and (3) a layer of substrate material different from said bonding alloy, said substrate material being selected from the group consisting of (a) metal carbide powder selected from the group consisting of tungsten carbide, titanium carbide, tantalum carbide and mixtures thereof containing sintering metal bonding agent therefor selected from the group consisting of cobalt, nickel, iron and mixtures thereof sinterable at operating temperature and pressure, (b) sintered metal carbide selected from the group consisting of tungsten carbide, titanium carbide, tantalum carbide and mixtures thereof, and (c) metal having a linear thermal expansion coefficient of less than about 10 .times. 10.sup.-.sup.6 inch per inch degree Centigrade and having a melting point at the operating pressure greater than the operating temperature and being selected from the group consisting of molybdenum, niobium, platinum, chromium, vanadium, tungsten, tantalum, titanium, silicon, rhodium, ruthenium, zirconium and alloys thereof, said substrate being disposed with one side facing said other two layers, b. disposing said metal container and the contents thereof within a finely-divided particulate pressure-transmitting medium that remains unsintered under the operating conditions of temperature and pressure and that transmits applied pressure substantially undiminished, c. applying substantially isostatic pressure to said container and said contents via said pressure transmitting medium, said pressure being greater than about 20,000 psi and significantly less than the pressure at which cubic boron nitride is stable at the operating temperature selected for this step, the application of pressure being maintained at least long enough to substantially stabilize the dimensions of said container and said contents at least in planes through said container parallel to the interface between the layers of bonding alloy or bonding alloy-providing metal and the cubic boron nitride crystals, d. simultaneously applying substantially isostatic pressure to and heating said container and said contents as substantially dimensionally stabilized in step (c), said heating being to a temperature and for a period of time in excess of about one minute to liquefy said bonding alloy or said bonding alloy-providing metal, exceed the critical wetting temperature of said bonding alloy and permit infusion thereof into capillary-size voids in said mass of cubic boron nitride crystals, said pressure being applied via said pressure-transmitting medium and reaching a value between at least about 500psi and a value significantly less than the pressure at which cubic boron nitride is stable at said critical wetting temperature, e. maintaining substantially isostatic pressure on said container and said contents during cooling thereof and f. recovering the resultant composite abrasive body in which a layer of bonding alloy-bonded cubic boron nitride crystals is directly bonded to a substrate. 2. The process of claim 1 wherein the bonding alloy provided is selected from the group consisting of NiAl in an amount of about 80-90% by weight nickel, CoAl in an amount of less than 20% by weight cobalt, FeAl in an amount of less than 15% by weight iron and NiCr in an amount of less than 25% by weight chromium. 3. The process of claim 1 wherein the initial pressure application is conducted in a first apparatus, the metal container and contents and the pressure-transmitting medium are transferred to a second apparatus and the simultaneous application of pressure and heating are conducted in said second apparatus. 4. The process of claim 3 wherein the pressure application in the second apparatus precedes the simultaneous application of pressure and heating. 5. The process of claim 3 wherein the heating in the second apparatus precedes the simultaneous application of pressure and heating. 6. The process of claim 1 wherein the substrate material is metal bonded sintered metal carbide. 7. The process of claim 6 wherein the metal bonded sintered metal carbide is cobalt bonded tungsten carbide. 8. The process of claim 1 wherein the substrate material is a metal carbide powder containing powdered metal bonding agent. 9. The process of claim 8 wherein the carbide powder is tungsten carbide and the metal bonding agent is cobalt. 10. The process of claim 1 wherein the metal container is open on one side, the bonding alloy or the bonding alloy-producing metal is placed in the bottom of said container and the mass of cubic boron nitride crystals is located between said bonding alloy or bonding alloy-producing metal and said substrate material. 11. The process of claim 1 wherein the mass of cubic boron nitride crystals are size-graded, the crystal sizes ranging from sub-micron size to greater than 40 microns. 12. The process of claim 1 wherein the cubic boron nitride content of the layer of metal-bonded cubic boron nitride crystals produced is in excess of 70 percent by volume. 13. The process of claim 1 wherein the substrate material is molybdenum. 14. The process of claim 1 wherein the substrate material is niobium. 15. A composite abrasive body consisting of a layer of bonding alloy-bonded cubic boron nitride crystals directly bonded to a metal substrate having a linear thermal expansion coefficient less than about 10 .times.10.sup.-.sup.6 inch/inch.degree. C, said metal substrate being selected from the group consisting of molybdenum, niobium, platinum, chromium, vanadium, tungsten, tantalum, titanium, silicon, rhodium, ruthenium, zirconium and alloys thereof, and the bonding alloy component of said layer of bonding alloy-bonded cubic boron nitride crystals being characterized as a metal alloy having a critical wetting temperature of less than about 1500.degree. C, exhibiting a limited finite reactivity with cubic boron nitride and being capable of reducing B.sub.2 O.sub.3, said bonding alloy component ranging from about 30 to 60% by volume of the cubic boron nitride crystals. 16. The composite abrasive body of claim 15 wherein the metal substrate is molybdenum. 17. The composite abrasive body of claim 15 wherein a layer of ceramic having a linear thermal expansion coefficient significantly greater than 10 .times. 10.sup.-.sup.6 inch/inch.degree. C is directly bonded to said metal substrate, said metal substrate being intermediate said layer of bonding alloy-bonded cubic boron nitride crystals and said layer of ceramic. 18. The composite abrasive body of claim 17 wherein the ceramic is alumina. Other info: Inventors: Lee, Minyoung (Schenectady, NY, US) Application Number: 515867 Filing Date: 1974-10-18 Publication_date: 1976-09-28 Assignee: General Electric Company (Schenectady, NY) Primary Class(es): 51/307 51/308, 51/309 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Arnold, Donald J. Assistant Examiner: Attorney: Binkowski; Jane M., Cohen; Joseph T., Squillaro; Jerome C. |
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