The decarburization behaviour during the sintering of metal-injection-moulded 420 stainless steel was investigated. Particular attention has been paid to the decarburization mechanisms and carbon distribution of parts sintered at different temperatures. The results indicate that the loss of carbon content occurs mainly through the reduction of surface oxides of powder particles or reaction with the atmosphere. Depending on the densification level, the sintering decarburization is separated into two stages. Below 1200 °C, decarburization occurs at the powder particle surface. The surface oxides react with the amorphous carbon or residual organics to pose the metal surface. At this time, the carbon content distribution of the sintered body is similar to that of the as-debound sample. The reduction of surface oxides promotes sintering. At 1200 °C, the densification speed is higher in the centre region of the sample, where the interconnected pores close and the second stage of decarburization takes place. At temperatures above 1200 °C, carbon atoms in the inner layers must migrate to the surface to react with the atmosphere. The decarburization speed is reduced and the carbon content distribution of the as-sintered part is similar to that of the dense decarburized part.

In this work, Ni_49.4Ti_50.6 Belleville washers are prepared by metal injection moulding (MIM). The martensitic transition temperatures and service performance of washers were investigated. The thermal hysteresis has reached 63.1–71.6°C, which is much higher than documented data in binary NiTi alloys. Ti₂Ni and Ni₄Ti₃ phase are observed in XRD patterns, which is responsible for the large thermal hysteresis. In the service tests, the restoring forces are higher than 40 kN, which are sufficient to ensure a tight connection of the fasteners. The loop resistance and high-current test have proved the safety of MIM NiTi Belleville washers compared to traditional steel spring washers, which can meet the challenge in complex outdoor circumstances.