Corrosion behavior of 17 - 4PH steel, produced by the MIM process, sintered in different atmospheres

Abstract

The Metal Injection Molding (MIM) process is used for small parts, complex geometries, and high production volumes. Among the various ferrous and non-ferrous alloys that use this technology, the precipitation-hardened stainless steel Catamold 17-4 PH stands out. This class of steel used in the aerospace and automotive industries is characterized by its resistance to corrosion combined with excellent mechanical properties. The sintering process of this steel is carried out in a controlled hydrogen-based atmosphere, which, together with the raw material, impacts the manufacturing cost of the components. In this work, different sintering atmospheres were evaluated, and the effects were verified using optical microscopy, scanning electron microscopy (SEM), the EDS microprobe, microhardness, and potentiodynamic polarization techniques. The results demonstrated that the microstructure and microhardness of the substrate were not affected. However, deleterious effects were detected with an increase in the level of porosity, compromising the corrosion resistance of the analyzed samples. Comparatively, samples with pure nitrogen showed better corrosion resistance compared to those with the presence of water vapor. However, it was less resistant to corrosion than found in the literature in a hydrogen atmosphere, considered the state of the art for Catamold 17 - 4 PH stainless steel.