Effects of laser scanning overlap rate on microstructure and properties of laser surface remelting stainless steel

Abstract

To study the effect of laser scanning overlap rate (LSOR) on the microstructure and properties of 304 stainless steel remelted layer (RL), nanosecond pulsed laser was used to remelt the surface of 304 stainless steel. The micro-morphology, hardness, roughness, adhesion force and corrosion resistance of RL are studied by changing the LSOR. The experimental results show that a layer of oxides mainly composed of Cr, Fe and Mn is formed on the surface of 304 stainless steel and the phase transition from α-Fe to γ-Fe after laser irradiation. Laser surface remelting (LSR) hardens the substrate surface with a hardness of 185 HV and the maximum hardness after remelting is 248.9HV. With the increase of LSOR, the surface roughness gradually increased, the adhesion force first increased and then decreased and the maximum adhesion is 26.1N. The LSOR at the turning point is 80% and the phase distribution of the RL is more uniform at this time. The maximum self-corrosion potential of the RL is -0.283V, which is positively shifted by 0.268V compared to the substrate self-corrosion potential. LSR is a promising technique to improve the surface microstructure and properties of 304 stainless steel.