Effects of nitrogen on predominant sintering mechanism during the initial stage of high nitrogen nickel-free stainless steel powder

In this study, gas-atomized Fe17Cr11Mn3Mo powders were nitrided to obtain different nitrogen contents for the purpose of studying the effects of nitrogen on predominant sintering mechanism during the initial stage of high nitrogen nickel-free stainless steel powder. Most of the nitrogen in both powders and sintered bodies was uniformly distributed in the form of solid solution, causing lattice distortion and thus hindering the diffusion of metal atoms. It was found that the higher the nitrogen content (0.19–0.84 wt%) in the sintered specimens, the lower the diffusion rate, and in turn the smaller the sintering-neck size. Theoretical analysis indicated that the predominant mechanism was surface diffusion. The additional activation energy caused by unit concentration of nitrogen hindering diffusion was 252.1 ± 40.4 kJ/mol, which was very close to the reported activation energy of nitrogen in FeCr steels. The results showed that the main obstacle to neck growth was solid solution nitrogen rather than surface nitrides. [Display omitted] •Most of the N in both powders and sintered bodies existed as solid solution.•The dominant sintering mechanism during the initial stage was surface diffusion.•The rate of diffusion decreased with increasing the sintered nitrogen content.•The main obstacle to neck growth was solid solution N rather than surface nitrides.•The activation energy that unit concentration of N hindering diffusion is 252 kJ/mol.