Laser alloying of aluminum alloy with Ni and Cr in order to prevent the formation of cracking was studied and a new nondestructive inspection technique. X-ray imaging, was applied to optimize the laser parameters. The effects of laser parameters on microstructure, microhardness and defects of the coating were evaluated. The results showed that the number and size of cracks and pores in the coatings increased with laser power and overlapping ratio. For a given laser power, there existed an optimum travel speed at which there were little defects in the coating. The hardness of the coating was 5–6 times that of the original substrate. Maximum hardness was found at a low laser power since higher powers led to dilution of the hard phases by aluminum from the substrate. By using X-ray imaging and SEM, the optimum process parameters were found which enable a smooth surface without any cracks and pores to be obtained.
|Surface and Coatings Technology
|Published - 23 Feb 1998