Microstructure and Wear Resistance of Laser Cladding Nano-Al2O3/MCrAlY Composite Graded Coating on TiAl Alloy

In this paper, the pure MCrAlY coating and nano-Al₂O₃ particles reinforced MCrAlY graded coating were prepared on TiAl base intermetallic alloy substrates by laser cladding process. Furthermore, the microstructure characterization, microhardness and wear resistance of the two kinds of MCrAlY coating were comparatively investigated with scanning electron microscope (SEM), HXD-1000TC hardness tester and MM-200 block-on-ring dry sliding wear tester. The results show that the laser-clad pure MCrAlY coating has a dendrite crystals characteristic. However, the graded composite MCrAlY coating consists of fine equiaxed grains because of addition of nanometer ceramic particles. Moreover, the grain size becomes small with increasing the nano-Al₂O₃ content in the coating. The microhardness and wear resistance of the composite coating is higher than that of the pure coating. The mainly wear mechanism of the pure MCrAlY coating is abrasive and delamination, while the mainly wear mechanism of the composites graded MCrAlY coating is abrasive.