Understanding the effect of Si3N4 nanoparticles on wear resistance behavior of electroless Nickel-Phosphorus coating through structural investigation

Abstract The incorporation of Si3N4 nanoparticles into the electroless Nickel-Phosphorous (Ni-P) coating matrix and the post-heat treatment has been carried out to study the microstructural evolution of the Ni-P-Si3N4 composite coating. The corresponding effects on the mechanical and tribological properties of the composite coating have been systematically investigated. The mechanism of the improved mechanical properties of the Ni-P-Si3N4 composite coatings after the heat treatment has been proposed in terms of changes in the crystal structure parameters. Shrinkage in the lattice parameters and the crystallite size of Ni and Ni3P crystals due to the presence of Si3N4 nanoparticles, the first-of-its-kind observation in electroless Ni-P coating systems, is found to be responsible for the improvement in the hardness and wear resistance of the Ni-P-Si3N4 composite coatings after the heat treatment. Raman spectroscopic study of the wear debris has also been carried out, identifying the signatures of graphitic Carbon and Nickel Oxide (NiO), which are attributed to the residual organic compounds and the oxidation of the Ni deposits in the electroless coating, respectively.