Method of producing thin, hard coating

Claim 1

A method of producing a thin, hard coating on selected surfaces of bearings, seal glands and cutting elements of rotary cone rock bit components by overlay coating said surfaces with an engineering ceramic comprised of at least one metallic element selected from a list consisting of Ti, Hf, Zr, Nb, Ta, W, B, Al, Co, and Cr, combined with at least one nonmetallic element selected from a list consisting of O, N, and C, by a modified physical vapor deposition process comprising the steps of: cleaning said surfaces of said components of said rock bit chemically, said surfaces to be free of residue, masking surfaces of said components which are to remain uncoated, loading said components into a vacuum coating chamber, locating at least one electric arc cathode metal vapor source spaced apart from said components in unobstructed view of said surfaces to be coated, said cathode is comprised of said metallic element, said cathode is cooperative with an anode, reducing atmospheric pressure within said chamber to about 1×10 -5 torr, supplying a high voltage bias of from about 500 volts to about 5000 volts to said components, said bias being negative with respect to said cathode, powering said vapor source to produce a first ionic plasma to further clean said surfaces and heat said components to a process temperature between about 200° Fahrenheit and about 400° Fahrenheit, supplying selected said nonmetallic element to said chamber as a reactant gas in quantity sufficient to raise said pressure within said chamber to about 1×10 -3 torr, lowering said high voltage bias to between about 50 volts to about 500 volts to maintain said process temperature, depositing said ceramic until a coating of between about 0.00005 inch and 0.001 inch thickness has been deposited, stopping said deposition process, raising pressure within said chamber to about one atmosphere, and removing said components from said chamber.

Claim 2

A method of producing a thin, hard coating on selected surfaces of bearings, seal glands and cutting elements of rotary cone rock bit components by overlay coating said surfaces with an engineering ceramic comprised of at least one metallic element selected from a list consisting of Ti, Hf, Zr, Nb, Ta, W, B, Al, Co, and Cr, combined with at least one nonmetallic element selected from a list consisting of O, N, and C, by a modified physical vapor deposition process comprising the steps of: cleaning said surfaces of said components of said rock bit chemically, said surfaces to be free of residue, masking surfaces of said components which are to remain uncoated, loading said components into a vacuum coating chamber, locating at least one electric arc cathode metal vapor source spaced apart from said components in unobstructed view of said surfaces to be coated, said cathode is comprised of said metallic element, said cathode is cooperative with an anode, reducing atmospheric pressure within said chamber to about 1×10 -5 torr, supplying a high voltage bias of from about 500 volts to about 5000 volts to said components, said bias being negative with respect to said cathode, powering said vapor source to produce a first ionic plasma to further clean said surfaces and heat said components to a process temperature between about 200° Fahrenheit and about 400° Fahrenheit, supplying selected said nonmetallic element to said chamber as a reactant gas in quantity sufficient to raise said pressure within said chamber to about 1×10 -3 torr, lowering said high voltage bias to between about 50 volts to about 500 volts to maintain said process temperature, depositing said ceramic until a coating of between about 0.00005 inch and 0.001 inch thickness has been deposited, stopping said deposition process, raising pressure within said chamber to about one atmosphere, and removing said components from said chamber.