Diamond coated WC and WC-based composites with high apparent toughness

摘要

A binderless coarse-grained WC substrate is coated with a chemical vapor deposition ("CVD") diamond layer in order to give a coating with improved adherence relative to WC--Co-based substrates and high compressive residual stress relative to Si.sub.3 N.sub.4 -based substrates. The elimination of Co from the WC improves the adherence of the diamond coating, allowing thicker coatings to be produced than for WC- -Co substrates. Thin coatings ( 30 &mgr;m) are acceptable for applications where the coating is under low applied stress. Thicker coatings ( 30 &mgr;m) are used to give enhanced damage resistance for stresses localized at the surface of the diamond-coated component. Applying the diamond coating to a WC/WC--Al.sub.2 O.sub.3 /WC graded composite allows materials with high damage resistance to be fabricated. Deposition of a substantially continuous diamond film may be accomplished by CVD and PVD techniques. WC ceramics allow faster deposition rates since Co in WC--Co enhances back-conversion of diamond to graphite, and diamond can therefore be deposited on WC at higher temperatures than WC-- Co substrates.