Comparative study on the friction-wear property of As-plated, Nd-YAG laser treated, and heat treated electroless Nickel-Phosphorus/Crab shell particle composite coatings on mild steel

Nickel-Phosphorus/Crab shell particle (NiP/CSP) composite coatings were prepared with different weight dispersions of CSP (0.5 g/l, 1.0 g/l, 1.5 g/l, 2.0 g/l, 2.5 g/l and 3.0 g/l) on mild steel using electroless coating process. Fabricated coatings were post treated with heat treatment and Nd:YAG laser treatment process and followed by a comparative study on surface morphology, surface hardness, phase structure, and friction-wear property with as-plated NiP and NiP/CSP composite coatings. The result showed the relative changes in the surface morphology of NiP/CSP composite coatings after Nd:YAG laser treatment. Dendrite structure was observed for laser treated coatings and its formation was affected by the incorporation of CSP in the NiP matrix. FeNi2P phase was formed for laser treated coatings in addition to the Ni3P and Ni12P5 phases. Higher surface hardness of 966 Hv(0.05) and 941 Hv(0.05) was achieved for laser treated NiP and NiP/CSP composite coatings compared to the heat treatment process and as-plated condition. On comparison with various weight dispersions, higher surface hardness of 941 Hv(0)(.05) was obtained for NiP/CSP (2.5 g/l) composite coatings as a result of the high diffusion of Fe element from substrate to the surface. Low friction coefficient was seen for the heat treatment process followed by the as-plated and laser treatment process. The formation of FeNi2P phase caused an increase in the friction coefficient for laser treated NiP and NiP/CSP composite coatings. However, there was an improvement in the wear resistance of laser treated coatings compared to the as-plated and heat treated coatings.