Grain Refinement and Property Trade-Offs in Laser Cladded Ni60-WC Coating Induced by 2% ZrO2 Addition

To improve the surface properties of Q235 steel, two types of composite coatings were prepared using laser cladding technology: a 25% WC + 75% Ni60 coating (Group NO) and a 25% WC + 73% Ni60 coating with 2% ZrO2 added (Group 2). Through XRD, SEM, microhardness testing, friction and wear testing, and electrochemical testing, the effects of ZrO2 on the phase composition, microstructure, mechanical properties, and corrosion resistance of the coatings were systematically investigated. The results indicate that upon the addition of ZrO2, Zr atoms solid-solve into the γ-Ni lattice, causing the grain size to refine from 17.36 nm to 10.84 nm, and the carbides to transform from coarse cuboidal particles (average 4.00 μm) into fine, irregularly shaped, dispersed particles (average 2.93 μm); the average hardness of the coating decreased from 901.51 HV0.2 to 576.20 HV0.2, but the uniformity of the hardness distribution improved significantly (standard deviation decreased from 142.75 to 29.74); the coefficient of friction increased from 0.71 to 0.85, and the wear volume increased from 0.04 mm3 to 0.38 mm3, indicating a decline in wear resistance; in a 3.5% NaCl solution, the corrosion potential shifted positively by 38 mV, and the corrosion rate decreased from 0.7234 mm·a−1 to 0.7071 mm·a−1, indicating a slight improvement in corrosion resistance. In summary, the addition of 2% ZrO2 achieves grain refinement, carbide homogenization, and improved corrosion resistance, but reduces hardness and wear resistance. It is suitable for operating conditions where corrosion resistance and microstructural uniformity are the primary considerations.