Diamond-coated hard metal member

A diamond-coated hard metal member, comprising:

• a hard metal substrate having a roughened surface;
• and
• a diamond coat layer coating the roughened surface of said substrate, either directly or with an interlayer containing a metal or metal compound interposed therebetween;
• wherein the roughened surface of said substrate is obtained by electrolytically etching a WC-based hard metal substrate comprising WC as a main component, said substrate contains an unetched portion having a metal element or metal compound and comprises a disperse phase having a sufficiently lower electrolytic etching rate than the WC dispersed therein in a surface region to at least a thickness that can be electrolytically etched in an amount of from 2 to 5 mol-%, and the surface of said unetched substrate has small diameter disperse phases having an average diameter of from not less than 0.5 μm to less than 2 μm in a density of from not less than 0.1/μm2 to not more than 0.2/μm2 or large diameter disperse phases having an average diameter of from not less than 2 μm to not more than 3 μm in a density of from not less than 0.03/μm2 to not more than 0.1/μm2, and said diamond coat layer or interlayer that directly coats said substrate has a roughened surface corresponding to the roughened surface of said substrate.

A process for producing a diamond-coated member, comprising the steps of:

• forming a hard metal substrate containing a disperse phase having a lower electrolytic etching rate than WC dispersed in the substrate;
• electrolytically etching the hard metal substrate to form fine projections having an average diameter of not more than 3.2 μm at the base thereof in a density of not less than 0.12/μm2;
• and
• forming a diamond coat layer on the surface of the electrolytically etched hard metal substrate, either directly or with an interlayer containing a metal or metal compound interposed therebetween, wherein the diamond coat layer or interlayer that directly coats the substrate has a roughened surface corresponding to the roughened surface of the substrate.

A process for producing a diamond-coating member, comprising the steps of:

• forming a hard metal substrate containing a disperse phase having a lower electrolytic etching rate than WC dispersed therein in a surface region to at least a thickness that can be electrolytically etched in an amount of from 2 to 5 mol-%, wherein the surface of the substrate has small diameter disperse phases having an average diameter of from not less than 0.5 μm to less than 2 μm in a density of from not less than 0.1/μm2 to not more than 0.2/μm2 or large diameter disperse phases having an average diameter of from not less than 2 μm to not more than 3 μm in a density of from not less than 0.03/μm2 to not more than 0.1/μm2;
• electrolytically etching the substrate to form a roughened surface thereon;
• and
• forming a diamond coat layer on the roughened surface of the substrate, either directly or with an interlayer containing a metal or metal compound interposed therebetween, wherein the diamond coat layer or interlayer that directly coats the substrate has a roughened surface corresponding to the roughened surface of the substrate.