Influence of Cr and Al on the Properties of Nitrided Cases of Steels

Abstract

Influence of Al and Cr on the properties of nitrided cases was studied for JIS-SACM645, SCM440 and SKD61 steels under as-nitrided (793K-216ks) and reheated (773 to 973K-3.6ks) conditions, using hardness measurement and X-ray diffraction analysis.
Hardness and residual stress distribusion in the nitrided case did not change under as-nitrided condition and reheated condioion at 873K for 3.6ks after nitriding for any of the three steels. SCM440 and SKD61 steels, containing Cr, showed good correlation between hardness of nitrided case and lattice strain induced by nitrogen atoms, while SACM645 steel, containing Al, showed no correlation. The hardening mechanism of nitrided case therefore differ between Cr containing steel and Al containing steel.