Effect of Laser Power on the Microstructure and Wear and Corrosion Resistance of Ni25 Alloy Coatings

This study systematically investigates the influence of laser power (1000 W, 1400 W, 1800 W) on the microstructure and properties of Ni25 alloy coatings prepared by laser cladding to optimize process parameters for enhanced comprehensive performance. Through the analysis of multi-dimensional characterization, it is found that the laser power significantly changes the thermal cycle, thus determining the evolution of microstructure. At 1000 W, a fine dendritic structure with dispersed hard phases (BNi3, BFe3Ni3, CrB2, Cr7C3) yielded the highest hardness (442.52 HV) but poor wear (volume loss: 0.3346 mm3) and corrosion resistance (Icorr: 2.75 × 10−4 A·cm−2) due to microstructural inhomogeneity. The 1400 W coating, featuring a uniform γ-Ni dendrite/eutectic network and increased B solid solubility, achieved an optimal balance with the lowest wear rate (0.0685 mm3), superior corrosion resistance (Icorr: 2.34 × 10−5; A·cm−2), and a stable friction coefficient (0.816), despite lower hardness (342.00 HV). At 1800 W, grain coarseness and Cr7C3 decomposition led to blocky hard phases, recovering hardness (415.36 HV) and reducing the friction coefficient (0.757), but resulting in intermediate wear and corrosion resistance. This study demonstrates that the uniformity and continuity of the microstructure are the key determinants governing the comprehensive service properties of the laser cladding layer, with their importance outweighing a single hardness index. 1400 W is identified as the optimal laser power, providing critical insights for fabricating high-performance Ni25 coatings in demanding service environments.