Study on laser surface remelting of plasma-sprayed Al-Si/1Â wt% nano-Si3N4 coating on AZ31B magnesium alloy

► As-plasma-sprayed Al-Si/1 wt% nano-Si3N4 coating was successfully remelted by laser. ► The laser remelted coating possessed an excellent metallurgical bonding to substrate. ► Some special structure existed in the composite coating. ► The remelted coating was mainly composed of Al, AlN, Al9Si, Al3.21Si0.47 and Mg2Si. ► Microhardness of remelted coating was enhanced to the range of 200-514HV0.05.