Fabrication and characterization of self-lubricating anti-wear 316L stainless steel/h-BN composite coatings on Q235 substrate via laser cladding

This paper presents the fabrication and characterization of self-lubricating, anti-wear 316L stainless steel composite coatings on a Q235 substrate using 316L stainless steel powders and nanoscale hexagonal boron nitride (hBN) ceramic particles via coaxial powder feeding laser cladding. The influence of process parameters on cladding quality and geometry, and the impact of h-BN contents (2 wt% and 5 wt%) on the microstructure and mechanical properties of the coatings were studied. Optimal process parameters for 316L/5wt%BN coatings were identified: a powder feeding rate of 3-4 rpm, a laser power of 2200-2400 W, a scanning speed of 4-5 mm/s, and an overlapping rate of 40 %. Microstructural analysis showed a smooth surface without cracks or pores. X-ray diffraction revealed intermetallic compounds such as CrB, Cr2N, Fe3N, BN, and gamma-(Fe, Ni). The inclusion of h-BN nanoparticles enhanced grain refinement, significantly increasing microhardness. Coatings with 5 wt% h-BN achieved an average microhardness of 438.8 HV10, 2.5 times higher than the substrate and the 316L stainless steel. Additionally, h-BN reduced friction coefficients, leading to substantial wear reduction. The 316L/5 wt% hBN sample experienced only 4.2 mg of wear, 45.16 % of the substrate's wear. These findings highlight the beneficial effects of h-BN nanoparticles on 316L stainless steel coatings, enhancing wear resistance, hardness, and overall performance.