Effect of Partial Fibre Laser Processing on the Wear Resistance of NiCrMoFeCSiB Coatings

Surface laser processing of metallic materials is known to be effective in improving wear resistance due to microstructure refinement and the associated hardening effect. However, the formation of cracks, which frequently accompanies such processing, remains a challenge. This work focusses on partial laser processing of Ni-based protective coatings as a method that could potentially reduce the risk of crack formation due to lower overall heat input and retaining softer material portions that facilitate stress redistribution. A fibre-optic laser with a wavelength of λ = 976 nm and beam oscillation capability was used. After laser processing at 175 W power, a 250 mm/min processing rate, and a 2 mm oscillation amplitude, coating hardness increased by ~1.49 times reaching 713 ± 19 HV0.2 value. Preheating the samples to 400 °C inhibited crack formation but partially reduced the quenching effect, providing a ~30% increase in coating hardness (631 ± 16NV0.2). The resistance to dry sliding wear was increased by ~2 times and to abrasive wear—by ~2.9 times. Partial laser treatment of 25%, 50%, and 75% of the surface area enhanced the coating’s wear resistance by 1.29, 2.13, and 2.81 time, respectively, indicating that when the processed surface area reaches 50% or more, wear resistance is primarily determined by the hardened regions and to a greater extent than what is expected based on the proportion of the treated area.