Effect of h-BN content on microstructures of the laser cladding self-lubricant coatings

Self-lubricating Ni+h-BN coatings were prepared by CO2 laser cladding with powder mixtures of Ni60 and h-BN. The chemical compositions and microstructures of the coatings were analyzed using SEM and XRD. The microhardness of the coatings was measured on a microhardness tester. It was found that the morphology of CrB was changed from irregular block-like shape (in Ni60+5%h-BN coating) -> short plate structure (in Ni60+10%h-BN coating) -> dendritic-plate structure(in Ni60+15%h-BN coating) with increasing the content of h-BN. The microhardness of the 5,10 and 15% h-BN coatings ranged from 650 similar to 800HV(0.2), 800 similar to 1010HV(0.2) and 1000 similar to 1200HV(0.2), which was higher than that of Ni60 coating and substrate.