Effects of σ phase in stainless steels on corrosive wear behavior in sulfuric acid

Generally, compound phases in alloys are harder than matrix and act as hard particles at dry wear condition. Such hard particles are helpful to reduce wear rate. However, the compound phases in alloys commonly act as cathodic phases in sulfuric acid media and can be sorted into two kinds. One is the strong cathodic phase that has low corrosion potential, such as Fe3C, Cr23C6, etc; another is the weak cathodic phase that even can be oxidized in sulfuric acid media, such as intermetallic compound phase σ. In this paper, the effects of σ phase in two kinds of stainless steels on corrosive wear behavior in sulfuric acid solution were investigated by using a modified corrosive wear tester, X-ray diffraction and scanning electron microscope, etc. Polarization curves and corrosion rates of the alloys were also measured. The results indicate that the corrosive wear rate decreases if there is a proper content of σ phase in the alloys. Therefore, a proper content of such a kind of intermetallic compound should be considered in design for corrosive wear resistant alloys used in sulfuric acid media.