Oxide Transformation During Sintering Of Prealloyed Water Atomized Steel Powder

Some amount of oxides are already present on the initial powder surface and its interior, however further oxide products formation and their transformation during sintering remains unclear. The present study deals with the modelling of oxides transformation in dependence on sintering atmosphere composition, its purity and temperature profile utilizing variety of chemical and thermodynamic softwares based on experimental results from interrupted sintering trials. As the base material prealloyed with chromium water atomized steel powder was used. The type, morphology and composition of oxide products on the fracture surface were studied by means of HR SEM combined with EDX analysis. Results indicate that oxide transformation processes occur in accordance with the thermodynamic stability of oxides, presented on the initial powder surface, in the line Fe2O3→FeO→Fe2MnO4→Cr2FeO4→Cr2O3→MnCr2O4→MnO. Amount and composition of surface products are strongly determined not only by conditions during dwelling at sintering temperature but also by processes during preceding heating stage