Nitriding Effect on HVAF FeMnCrSi Coating

Plasma nitriding is an appropriate way to improve the surface hardness of materials and prevent wear. Using plasma nitriding can result in a unique combination of bulk and surface properties. Some studies indicate defects, and residual stresses in the crystal lattice are some of the most influential factors for nitrogen diffusion during the nitriding process. As thermally sprayed coatings exhibit a high degree of deformation due to particle impact, a high degree of defects and stress is expected. This work aimed to study the effect of the glow discharge plasma nitriding on FeMnCrSiNi coating deposited by the HVAF process. The formation of expanded austenite and chromium nitride on the HVAF coating was observed, followed by a significant hardness increase. The nitride coating showed improvements in wear resistance and coefficient of friction. The coating after heat treatment showed a higher wear rate, showing the significant role of residual stress for this coating. Therefore, surface nitriding has the potential to increase the lifespan of the coating. In addition, the formation of chromium nitride on the surface decreased the corrosion resistance of the coating in 3.5wt.%NaCl solution, making it more prone to general and pitting corrosion.