Effects of High Oxygen Content on the Densification Behavior of 316L Stainless Steel During the Later Sintering Stage

In this study, gas-atomized 316L stainless steel powders were oxidized to obtain a high oxygen content (0.09–0.60 wt.%) to study the dominant sintering mechanism of water atomized grade powders in the later stage of sintering. At 1360°C, particles with high oxygen content were distributed at grain boundaries and within grains in the form of oxides rich in Si and Mn, obstructing the channels of atomic diffusion dominated by volume diffusion. The higher the oxygen content, the lower the diffusion rate, and in turn the lower the densification rate is. The activation energy caused by the unit concentration of oxygen was 16.57 kJ/mol, which was much lower than the bonding energy of M-O (M = Fe, Cr, Si, Mn, Mo, etc.). The results showed that volume diffusion in the later stage of sintering tended to bypass the oxide particles rather than breaking the chemical bonds of M-O.