EFFECT OF QPQ TREATMENT ON THE PERFORMANCE FOR H13 DIE STEEL

Abstract

QPQ salt bath treatment of H13 steel was conducted by nitriding at the same temperature of 565℃ for various times, followed by the same post-oxidation process. Optical microscope, micro-hardness tester, X-ray diffraction and wear resistance tester were employed to characterize the microstructure, phase constituents, micro-hardness and wear resistance of the treated specimens. The results showed a compound layer mainly composed of ε-Fe2-3N and diffusion layer were formed during salt bath nitriding and a thin oxide layer composed of Fe3O4 was formed by post-oxidation, and the compound layer thickness increases with the nitriding time. The maximum surface hardness value of 1441 HV0.3was obtained after nitriding at 565℃ for 150 min, which is as three times high as that of untreated sample. Meanwhile the wear resistance of H13 steel is significantly improved by QPQ treatment, 150 min is the optimum nitriding time to improve the surface hardness and wear resistance of H13 steel.