Enhance the corrosion resistance of cast iron surfaces by pre-vacuum nitriding

To enhance the corrosion resistance of the cast iron surface, its application in extreme conditions has been expanded. The study investigates the microstructure evolution and corrosion behavior of the nitriding layer created through pre-vacuum nitriding. X-ray diffractometer (XRD) analysis reveals the presence of Fe₃N and Fe₄N in the nitriding layer. The compound layer has a thickness of approximately 10 μm. The hardness of the nitriding layer is more than twice that of the substrate, measuring at 560.2 HV₁. In comparision to the substrate's corrosion current density of 5.45 × 10⁻⁶ A/cm², corrosion potential of −0.697 V and corrosion rate of 63.4 μm/year, the nitrided layer shows significant improvements: the corrosion current density is reduced by 68%, the corrosion potential shifts to a positive 0.104 V, and the corrosion rate decreases by 65.9%. Additionally, nitrided layers exhibit outstanding friction-reducing properties, with the friction coefficient reduced by 13% compared to the substrate.