Cracking behavior of AISI 316L stainless steel powder by gas nitriding and its influence on spark plasma sintering

Abstract

In this study, the effect of nitriding temperature on the deformation behavior of spherical AISI 316L powders was investigated. The results showed that the nitrogen content in powders was significantly increased by increasing the nitriding temperature under ammonia atmosphere. However, the resulted residual stress led to the deformation or even cracking in powders, the cause of drastic changes in the bulk density and fluidity of powders. Furthermore, the microstructure and properties of alloys synthesized by spark plasma sintering were also analyzed. The obtained results also indicate that the powder deformation has no influence on the consistency of sintered samples, but the nitriding temperature of AISI 316L powder obviously affects the morphology and performance of sintered samples. Nitrogen initially exists as interstitial atom in the steels till the nitriding temperature rises to 500 °C where nitrides begin to precipitate in the sample. Such morphological transition of nitrogen atoms has a significant impact on the mechanical properties of the alloys. The better corrosion resistance of the alloy prepared over 500 °C in 3.5 wt.% NaCl solution shows that the nitriding temperature also matters for corrosion performance.