Effects of post heat-treatment on microstructure and tribological properties of Ni60/H-BN self-lubricating anti-wear composite coating on 304 stainless steel by laser cladding

The Ni60/h-BN self-lubricating anti-wear composite coatings were prepared on 304 stainless steel substrate by laser cladding, and the composite coatings were heat treated at 600℃ (stress relief annealing) for 1 h and 2 h, respectively. The differences of the phase compositions, microhardness and tribological properties of the composite coatings after heat treatment have been investigated. Results indicate that the coating after heat treatment for 1 h had the highest microhardness (about HV_0.5765.0). For the best tribological properties under 10 N dry sliding wear test condition, the friction coefficient was 0.53, the wear rate was 3.37×10^-6 mm/ (Nm) and the wear mechanism was mild abrasive wear. The friction coefficient and the wear rate of the coating without heat treatment were 0.53 and 6.39×10^-6 mm/ (Nm), respectively. The wear mechanism was the combination of brittle fracture, adhesive wear and abrasive wear. The friction coefficient and the wear rate of the coating after heat treatment for 2 h were 0.39 and 5.29×10^-6 mm/(Nm), respectively. The wear mechanism was mainly abrasive wear and mild adhesive wear. In this paper, the laser clad self-lubricating anti-wear composite coating after heat treatment for 1 h presented the highest microhardness and the most excellent tribological properties.