PREDICTION, FORMATION AND ANALYSIS OF MICROSTRUCTURE OF HIGH CHROMIUM-ALLOYED PM STAINLESS STEEL SINTERED IN DIFFERENT ATMOSPHERES

Analysis of the microstructure of high chromium alloyed PM stainless steel was performed in several stages. The equilibrium phase diagrams and mass fractions of phases for alloy Fe-20%Cr-17%(Ni,Si,Mn)-C were calculated using Thermo-Calc and JMatPro software. All calculations were done for two nitrogen content levels, which correspond to compositions of material sintered in N2-H2 and atmosphere without nitrogen (pure H2 and argon), respectively. According to calculations, austenite and chromium carbides are in equilibrium if sintering is an in atmosphere without nitrogen, and austenite with chromium carbonitrides and carbides for material sintered in N2-H2 atmosphere. The microstructure of the materials is affected by the sintering atmosphere, especially at the surface. The influence of sintering atmospheres on microstructure was analyzed. The results showed that the predicted microstructure is in good agreement with observed real microstructure