Effect of laser remelting on surface composite layer of nickel aluminide coated steel substrate

Surface modification of coated metallic materials through laser re-melting technique is a fast growing and promising research field. In this study, nickel-aluminide coating was deposited on medium carbon steel via plasma spraying technique. Subsequently, nickel-aluminide coating was modified by laser re-melting and rapid solidification. The effect of laser processing parameters was also studied by selecting a number of energy densities. The laser modified specimens were characterized with the help of optical microscope, scanning electron microscope equipped with energy dispersive X-ray spectrometer, and microhardness tester. The results showed that the laser modified zone composed of ultra-refine grain structure. The depth and width of the laser melted zone/bead was found correlated with laser beam travel speed and energy density. Vickers microhardness results showed that the hardness of the laser modified surface was increased by three times with respect to the base metal. Moreover, microhardness of the laser melted zone was found dependent on the laser beam energy.