Two-stage sintering of nano-sized yttria stabilized zirconia process by powder injection moulding

Powder injection moulding (PIM) is capable of mass producing intricately shaped components. In recent years, this technology has been adopted in the electronic, computer, chemical and medical industries. The 3 mol% yttria stabilized zirconia (Y-TZP) is well recognised for its high fracture toughness. PIM of nano-sized Y-TZP hence offer attractive potential applications. Grain growth however is a major problem for nano-sized powder. Initial researches proposed that high green density and minimum sintering temperature are beneficial in controlling the grain growth of nano-sized powder. In view of the constraint of low green density of PIM samples, grain growth control will be even challenging. Two-stage sintering (2SS) is reported to be able to refine the microstructure and enhance the material properties. This method simply modifies the sintering route by firing the sample at high temperature follow by rapidly cooling down and dwelling at lower temperature. The objective of this work is to monitor the effect of 2SS on the nano-sized Y-TZP process by PIM. Dimensional changes, weight loss, density, hardness as well as microstructure are study after the sintering and compare to the conventional isothermal sintering. The process condition at 1350 °C follow by 900 °C is found to be able to achieve comparable hardness as isothermal sintering at 1500 °C. With a finer microstructure, 2SS can potentially improve the grain size dependant material properties of nano-Y-TZP in the near future.