Structural aspects of strength and methods to increase the serviceability of carbide coatings

The effect of composition and structure on the microhardness, plasticity parameter (δ_H) and fracture toughness (K_Ic) of the widely used carbide layers (TiC, ZrC, VC, NbC, Cr₂₃C₆, Cr₇C₃) was investigated. It was found that the microhardness and plasticity parameter were basically determined by the composition of the carbide coatings and did not substantially vary with the structure, which had a preferential effect on fracture toughness. The laws governing the influence of grain shape, size, and preferred orientation on the fracture toughness of the coatings were determined. Recommendations for the control of composition and structure were formulated, and methods developed for the deposition of carbide coatings which increased the durability of a hard-alloy tool used under severe conditions two-fold compared to the best known analogues. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(411), pp. 97–106, January–February, 2000.