Processing of Stainless Steel (SS316L)-Hydroxyapatite (HA) Powder Composite through Powder Injection Molding

Abstract

The combination of a metallic bioinert material, stainless steel 316L (SS316L) and a bioactive material, hydroxyapatite (HA) can produce a composite material which has superior properties for orthopaedic applications. The main objective of this study is to investigate the effects of sintering temperature and time on the physical and mechanical properties of the sintered part. 50wt.% of SS316L and 50wt.% of HA were mixed with a binder system which consisted of palm stearin (PS) and polyethylene (PE) for 61.0vol.% powder loading. Rheological properties show the pseudoplastic behavior of the feedstock, where viscosity decreases with increasing shear rate. The feedstock was injection moulded into a tensile bar shape while thermal debinding was carried out at 320°C and 500°C. The brown part was sintered at 1000, 1100, 1200 and 1300°C, with three different sintering times of 1, 3 and 5 hours in the furnace. The highest sintered density measured was 95.61% of the theoretical density. The highest hardness and Young’s modulus measured were 150.45HV and 52.61GPa respectively, which is higher than the human bone. The lowest percentage of carbon content was 0.022 wt.% when the sample sintered at 1300°C for 1 hour. Mechanical and physical properties show that the SS316L/HA composite was successfully produced through the PIM process and can be potentially used for medical applications.