LASER ALLOYING OF ALUMINUM-ALLOY AA-6061 WITH NI AND CR - PART 1 - OPTIMIZATION OF PROCESSING PARAMETERS BY X-RAY-IMAGING

Laser alloying of aluminum alloy with Ni and Cr in order to prevent th e formation of cracking was studied and a new nondestructive inspectio n technique, X-ray imaging, was applied to optimize the laser paramete rs. The effects of laser parameters on microstructure, microhardness a nd defects of the coating were evaluated. The results showed that the number and size of cracks and pores in the coatings increased with las er power and overlapping ratio. For a given laser power, there existed an optimum travel speed al which there were little defects in the coa ting. The hardness of the coating was 5-6 times that of the original s ubstrate. Maximum hardness was found at a low laser power since higher powers led to dilution of the hard phases by aluminum from the substr ate. By using X-ray imaging and SEM, the optimum process parameters we re found which enable a smooth surface without any cracks and pores to be obtained. (C) 1998 Elsevier Science S.A.