Effect of MoO3 on the microstructure and tribological properties of laser-clad Ni60/nanoCu/h-BN/MoO3 composite coatings over wide temperature range

Abstract The samples of nickel-base self-lubricating composite (Ni60/nano-Cu/h-BN) (NSLC) with different additive amounts of MoO3 were manufactured by laser cladding on substrates of Q235 steel. The microstructure and hardness of the as-fabricated NSLCs were investigated. The wear and tribological behaviors of the NSLCs with and without MoO3 from 25 °C to 800 °C were discussed. The results revealed that the addition of MoO3 resulted in the hardness improvement of the NSLCs due to the formation of Mo2C and Cr (Mo)-rich reinforcements during laser cladding process. The NSLC with 4 wt% MoO3 addition showed the best wear performance from 25 °C to 800 °C. At 600 °C and 800 °C, MoO3 solid lubricant was regenerated by oxide reaction during the wear process. Meanwhile, CuMoO4 was generated owing to a tribo-chemical reaction at high-temperature. These solid lubricants formed a lubricating transfer film, which improved the tribological properties of the coating.