Machinable ceramic substrate for CVD diamond coating

Newly developed machinable metallic ceramic titanium silicon carbide, Ti3SiC2, was successfully used as a substrate for CVD diamond coating. This metallic ceramic was synthesized from a mixed powder of Ti, Si and TiC. The powder was sintered in a graphite mold at 1573 K for 15 min under a constant pressure of 50 MPa. Two types of specimens, (1) a plate of 50-mm diameter for a linear slider and (2) a rod and ring pair for a rotating bearing of 8-mm diameter and 10-mm length were prepared. On the flat surface of the plate, CVD diamond film of approximately 10-mum thickness was deposited by the microwave CVD method. Diamond film was also deposited both on the inner surface of the ring and on the outer surface of the rod by the hot filament method. Diamond-coated surfaces of all specimens were polished up to a surface roughness, R-a, of approximately 0.2 mum. Coefficients of friction between the polished diamond plate and a stainless steel rail, specimen (1), and between the rotating rod and a stationary outer ring, specimen (2), were measured. The lowest coefficients of friction in both specimens were less than 0.01. (C) 2003 Elsevier B.V. All rights reserved.