Microstructure and mechanical properties of microwave-stepped-sintered SS316L-5 wt.% HA composites

This study reports the development of SS316L composites with 5 wt.% hydroxyapatite (HA) using hybrid microwave step-sintering. Nanosized HA was uniformly blended with SS316L powder and sintered at temperatures ranging from 1050 °C to 1350 °C. The sintering schedule included intermediate holding stages before and after the peak temperature was reached. This study systematically investigated the effects of sintering temperature on phase evolution, microstructural development, elemental distribution, densification, porosity and microhardness. X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS), porosity analysis and Vickers microhardness testing were employed. The composite sintered at 1250 °C exhibited optimal performance, with a relative density of ∼89% and the highest microhardness of 473 HV0.05. Sintering at 1350 °C led to elemental segregation and secondary phase formation, causing microstructural instability.