The key technology of heat treatment using micro-shot peening to save energy and reduce carbon constructed for the green process of metal injection molding

Metal powder injection molding (MIM) is a near net-shape manufacturing method, but also a high-energy-consuming industry. The MIM process includes several technical steps from the mixing, granulating, injection molding, de-binding, sintering, heat treatment and other secondary operation to products. Nowadays, the worldwide research is focusing on energy saving, carbon reduction and sustainable development. In response to the trend of energy reduction and expensive energy prices, improving the efficiency of energy use is an inevitable approach. Meanwhile, it can deal with issues such as carbon tax and fee. There is a reduction in CO2 emissions to reduce the effect of global greenhouse gases. The nitriding heat treatment in MIM consumes a lot of energy and generates a lot of carbon emissions. In this study, micro shot peening can give very large compressive residual stress on the surface of the MIM product. The shot peening can greatly improve the mechanical properties of the product. It helps shorten subsequent heat treatment time by more than 50%. Moreover, the depth of the nitrided layer and the hardness of the product still meet the requirements for industrial applications. Through shot peening to achieve green manufacturing, it can reduce the carbon footprint of MIM's heat treatment.