Interfacial Reaction Induced Synergetic Strengthening Effects on the Plasma Sprayed Ni3Al Composite Coating Reinforced with Hexagonal Boron Nitride Nanoplatelets

Ni3Al has shown great potential in high-performance wear-resistant coating material for lots of tribological machinery components working in extremely aggressive environments owing to its anomalous strength -temperature dependence and coexistent atomic bonds (covalent and metallic bonds) in nature. In this research, hexagonal boron nitride nanoplatelet (BNNP) reinforced Ni3Al composite coatings are fabricated on Ti(6)Al4V substrate using plasma spray. The added BNNP can survive the harsh high-temperature conditions and are homogeneously distributed in the composite coatings. Trace amounts of in-situ synthesized AlN and AlB2 and local diffusion layer are found to form a stronger BNNP-Ni3Al interface in such a way that BNNPs act as anchors bonding Ni3Al matrix during rapid solidification. These BNNPs either locating within a splat or being sandwiched by the adjacent splats exert synergetic strengthening effects on individual splats and splat boundaries, imparting the lamellar structural composite coatings with noticeably improved mechanical and tribological properties. As compared with Ni3Al coating, BNNP/Ni3Al composite coatings showed an improvement in tensile strength, elongation, toughness, and wear resistance by 24.6 %, 21.4 %, 52.5 %, and 77 %, respectively. This research is expected to shed some light on BNNP potentials for designing and producing high-performance composite coatings using plasma spray.