Effect of laser specific energy on microstructure and properties of Nano-TiC/15-5PH composite coatings on 17-4PH by laser cladding

Laser specific energy is a critical parameter that reflects the energy efficiency of laser cladding, directly influencing the microstructure and mechanical properties of the composite coatings. To enhance the wear resistance of 17-4PH stainless steel and ensure its applicability in industrial settings, the nano-TiC/15-5PH composite coatings were prepared on 17-4PH stainless steel by laser cladding to strengthen the surface. The effect of laser specific energy on the phase composition, microstructure, microhardness, and wear resistance of composite coatings was systematically investigated by varying either the laser power or the scanning speed. The optimal process parameters corresponding to laser specific energy were identified to achieve enhanced wear resistance for the composite coating. The results show that the composite coatings are mainly composed of α-Fe, (Fe, Ni), (Fe, Ni)₂₃C₆ and TiC. The composite coatings exhibit a similar microstructure at varying laser specific energies, with the dendrites gradually becoming finer from the bottom to the top. Furthermore, both the average friction coefficient and microhardness of the composite coatings exhibit an initial increase followed by a decrease as laser specific energy rose. The maximum hardness achieved is 445.64 ± 3.8 HV_0.5, representing a 1.2-times increase compared to 17-4PH stainless steel. Specifically at a laser specific energy of 200 J/mm², with a corresponding laser power of 2000 W and a scanning speed of 5 mm/s, the average friction coefficient and wear volume reached their minimum values at 0.2629 and 27.458 × 10^-5 mm³. The composite coating demonstrated optimal wear resistance characteristics.