Microstructure and mechanical properties of a new group of nanocrystalline medical-grade stainless steels prepared by powder metallurgy

Abstract

This paper focuses on the structure and mechanical properties of powder metallurgy stainless steels (Fe–Cr–Mn–Mo–Si–N–C) developed for biomedical applications. The samples were prepared by mechanical alloying and subsequent liquid-phase sintering with a eutectic Mn–Si alloy additive. By changing the sintering aid content, the pore configuration, compressive strengths, and impact properties of the samples were assessed. The Rietveld X-ray diffraction analysis showed after sintering at 1050°C for 60min followed by water-quenching, a nanocrystalline austenitic structure was formed in the material. According to the mechanical experiments, by increasing the additive content from 0wt% to 6wt%, sintering densification, yield stress, compression strength, and absorbed impact energy were improved, where spoiling occurred when adding 8wt% additive. Also, as realized from the impact fracture surface features, despite the presence of some unmelted additive particles, the role of the pore elimination in toughness prevailed over that of these particles.