Effect of Y2O3 Addition on Microstructure and Properties of In Situ Ceramic Particle-Reinforced Nickel Matrix Composite Coatings

In this study, Ni-based composite coatings with (Cr, V) B-2 ceramic particles were reinforced using varying Y2O3 concentrations for crack-free layers on 40CrNiMo steel surfaces. We investigated the phase composition, microstructure, microhardness, wear resistance, fracture toughness, and the reinforcement mechanism of Y2O3 within the composite cladding. Using SEM and TEM, we revealed the pivotal role of rare earth oxide Y2O3 in refining grains and forming uniform, densely-packed microstructures in the coatings. The resulting cladding layer mainly consisted of fine, strip-like precipitates of the gamma-Ni phase, along with ceramic reinforcement particles like CrB2, VC, and VB2. Unmelted Y2O3 and preferentially nucleated VC served as nucleation sites for (Cr, V) B-2 particles, contributing to the overall structural integrity. Our findings showed that an optimal quantity of Y2O3 moderately increased the hardness to a maximum of 1049.4 HV0.2. Additionally, with increased Y2O3 content, the cladding layer exhibited enhanced wear resistance, improved fracture toughness, and reduced susceptibility to cracking due to complete plastic deformation. However, excessive Y2O3 addition led to a decline in wear resistance, emphasizing the importance of carefully controlling Y2O3 content for optimal coating performance. These results highlight the potential for Y2O3 to enhance Ni-based (Cr, V) B-2 ceramic particle composite coatings, positioning them as promising candidates for advanced surface enhancement applications in materials science and engineering.