KINETICS ANALYSIS OF HIGHER TEMPERATURE SALT BATH NITRIDING FOR AISI 1045 STEEL

Abstract

Rapid salt bath nitriding was conducted at higher temperature above 600[Formula: see text]C instead of normally used 560[Formula: see text]C for AISI 1045 steel. Optical microscopy (OM), X-ray diffraction (XRD) and micro-hardness tester were employed to characterize the microstructure, phase constituents and micro-hardness of the treated specimens. The results showed that salt bath nitriding at higher temperature could significantly increase the compound layer thickness and higher cross-sectional hardness can be obtained. Kinetics analysis illustrated that the nitrogen atoms diffusion coefficient was obviously increased with temperature, and the activation energy of nitrogen atom diffusion was decreased from 220[Formula: see text]kJ[Formula: see text]mol[Formula: see text] to 142[Formula: see text]kJ[Formula: see text]mol[Formula: see text].