Surface Modification by Laser Cladding of Ni-Cr-Al-Y Alloy

Ni-22mass%Cr-10mass%Al-lmass%Y (NiCrAlY) alloy, Al, Nb carbide, and Cr carbide added NiCrAlY alloy were deposited on to mild steel substrate using laser cladding. Crack free clad layers were obtained at laser power of 2.5kW, defocus length of 25mm and traverse speed of 5mm/ks. Laser clad NiCrAlY alloy and Al added NiCrAlY alloy exhibited superior oxidation resistance because of formation of an Al2O3 protective scale. Spalling of oxide scales reduced the oxidation resistance of laser clad Nb carbide and Cr carbide added NiCrAlY alloy in comparison with NiCrAlY alloy clad layer. Wear resistance of laser clad NiCrAlY alloy enhanced after a surface oxidation treatment because of a lubricating effect of the oxide scale. Al addition has no advantageous effect on wear resistance of laser clad NiCrAlY alloy. Laser clad Nb carbide added NiCrAlY alloy has superior wear resistance regardless of the oxidation treatment. Wear resistance of laser clad Cr carbide added NiCrAlY alloy was also improved by the oxidation treatment. However, degradation of the wear resistance did not occur after removing the oxide scale. Thus, the improvement seems to be caused by an effect of carbides precipitated in the clad layer during the oxidation treatment.