Microstructure - tensile strength correlation of salt bath nitrocarburised engineering steels

摘要

A commonly used engineering steel (En8) and a hot working die steel (H11) were salt bath nitrocarburised in the ferritic and austenitic range and studied for their microstructure and tensile properties. Compound layer thickness and hardness increased with increasing treatment temperature. There was a marginal improvement in the tensile strength after ferritic nitrocarburising due to the hardness increase in the compound layer and diffusion zone. There was marginal drop in the tensile properties of specimens treated in the austenitic range, but these values were comparable to those obtained after blank treatment at the same temperature. The tests showed that the compound layer had good cohesion with the underlying zone despite the precipitous hardness drop at their interface.