Laser surface alloying with carbon on 15-5PH steel for improved wear resistance

Supersaturated carbon alloying layer was prepared on the surface of 15-5PH stainless steel using laser surface alloying technology with carbon powders as alloying materials. XRD, optical microscope, scanning electron microscope, microhardness test and wear test were performed to characterize the microstructure and wear resistance of substrate and alloying layer. Results showed that the alloying layer was rapidly solidified dendritic structure with phase compositions of high-carbon austenite and a small amount of martensite and M7C3 carbides. Microhardness of the alloying layer reached about 510 HV, which was 38.7% higher than that of the as-deposited substrate (375 HV). Carbon supersaturated solid solution strengthening and microstructure refinement strengthening were the main reasons for a substantial increase in alloying layer microhardness. After direct aging treatment, microhardness of the alloying layer further increased to nearly 640 HV. Wear test results showed that the mass loss of the aging alloying layer was about 60% lower than that of the aging substrate, which meant significantly improvement of wear resistance.