CVD diamond coating annulus components and method of their fabrication

A method for improving the abrasion resistance of the annular interior surface of an annulus having an exterior surface, which comprises the steps of:

• (a) placing said annulus in a chamber and heating to an elevated CVD diamond-forming temperature;
• (b) providing a hydrogen/hydrogen gaseous mixture within said chamber;
• (c) at least partially decomposing said gaseous mixture in said chamber to form a CVD diamond layer on substantially the entire interior and exterior surface of said annulus;
• and
• (d) quenching said annulus by rapidly reducing the temperature of said annulus for removing said CVD diamond layer from said exterior surface of said annulus by spalling while retaining said CVD diamond layer on said interior surface of said annulus, said annulus being formed of a material having a higher coefficient of thermal expansion than diamond sufficient for enhancing retention of diamond within said annular interior surface due to compressive forces and removal of diamond on said exterior surface during said quenching due to spalling.