Stainless steel 316L–hydroxyapatite composite via powder injection moulding: rheological and mechanical properties characterisation

Abstract

Powder injection moulding is a manufacturing process capable of producing complex, precise and net-shaped components from metal or ceramic powders at a competitive cost. This study investigated the rheological properties of stainless steel 316L–hydroxyapatite composite by using palm stearin and polyethylene as a binder system, evaluates the physical and mechanical properties, and composition change of the sintered part at different temperatures through powder injection moulding process. Stainless steel 316L powder was mixed with hydroxyapatite by adding a binder system (palm stearin and polyethylene) at 58·0 vol% powder loading prepared via critical powder volume percentage. A green dumbbell-shaped part was produced via plunger-type injection moulding. The green part was sintered at 1000, 1100, 1200 and 1300°C at 3 hours. The value of flow behaviour index n is from 0·1 to 0·39, which is within range of the injectability index. The obtained activation energy is 5·75 kJ mol−1. Morphological results indicate the formation of pores at a sintering temperature of 1000°C, a decrease of pores when the temperature is increased, and the occurrence of densification. At 1300°C it showed the highest mechanical properties of Young's modulus which is 41·18 GPa. The decomposition of hydroxyapatite into β-tricalcium phosphate and tetracalcium phosphate phases started to occur at 1000 and 1100°C, respectively. The highest sintered density is 3·7744 g cm−3 which is close to the density of hydroxyapatite but the mechanical properties is higher than pure hydroxyapatite.