Recently, metal injection molding (MIM) has emerged and rapidly developed as a powder metallurgy net-shaping process. Increasing attention has been paid to this process as a promising technology to produce small parts with complex geometric shapes [1,2]. Although MIM process is a cost-effective technology to precisely fabricate large quantities of small and intricate parts, researchers and manufacturers are highly concerned with the costly raw materials used in the process [3]. Such costly applications of MIM involve fine (< 10-20 µm) powders with spherical particle shape that are typically manufactured by gas atomization (GA) process. However, the cost of applying MIM to stainless steel (SS) powder with irregularly shaped particles using water atomization (WA) process is only one fifth of that

The effects of Nb and C addition on the corrosion performance of metal-injection-molded 440C martensitic stainless steel were investigated. In addition to 440C and Nb440C samples, samples with different carbon contents were prepared from the Nb440C pre-alloyed powder mixed with graphite powders. The results show that Nb is uniformly distributed in the matrix in the form of carbides. This can reduce the activity of C in the matrix and inhibit grain growth. The corrosion resistance of all the samples was characterized by anodic polarization, electrochemical impedance spectroscopy, and double-loop electrochemical potentiokinetic reactivation analyses. The added Nb consumes C atoms in the matrix, allowing more Cr atoms to diffuse to the surface to form a passive film. As a result, resistance to pitting corrosion and intergranular corrosion is improved. However, increased carbon content negatively affects corrosion resistance.