Laser shock wave-induced wear property improvement and formation mechanism of laser cladding Ni25 coating on H13 tool steel

Abstract

• The Ni25 coating was fabricated by laser cladding to repair the damaged components. • LSP treatment was applied on the Ni25 coating for surface strengthening. • Columnar dendrites in the top region were transformed into refined equiaxed dendrites. • Influence mechanisms of LSP on the microstructural evolution were revealed. H13 steel is frequently subjected to the high-strength alternating stress and cyclic thermal load impact, the Ni25 coating was prepared by laser cladding (LC) on the worn surface of H13 tool steel to repair the damaged components. As the residual stress induced by LC in the Ni25 coating, laser shock peening (LSP) was combined to further improve the stress distribution and strengthen the mechanical performance. The influences of LSP treatment on the microstructure and mechanical performance were systematically studied. Results showed that after LSP treatment, columnar dendrites in the surface layer with a depth of 0.28 mm were transformed into refined equiaxed dendrites. Meanwhile, the residual stress was completely converted from tensile state into compressive state, and the micro-hardness was also enhanced by 27.3 %, with the peak of 550 HV. Consequently, the coefficient of friction (COF) and wear rate of Ni25 coating were decreased significantly. Finally, extra attentions were paid to the laser shock wave-induced formation mechanism improvement in wear property of laser cladding Ni25 coating on H13 tool steel.