Tribological Behavior of ZL205A Al-Alloy Modified with Laser Cladded Al₂O₃-Doped NiCrAl Coatings

The surfaces of ZL205 A Al-alloy,a good automobile valve material,were modified with the Al₂O₃-doped NiCrAl coatings synthesize by laser cladding of Ni,Al and Al₂O₃ powders. The microstructures and tribological properties of the Al₂O₃-doped NiCrAl and Al₂O₃-doped NiCrAl coatings were characterized with X-ray diffraction,scanning electron microscopy and conventional mechanical probes.The results show that when it comes to tribological properties,the Al₂O₃-doped NiCrAl coating outperforms the NiCrAl coating.For example,the Al₂O₃-doping decreased the friction coefficient,increased the hardness of NiCrAl coatings from 350 to 650 HV and decreased the wear-rate of NiCrAl coatings by 30%,possibly because the randomly distributed well-dispersed Al₂O₃ particles effectively prevented the growth of dendric textures in laser cladding,resulting in significant reductions of both the grain-size and plasticity of the uniform,smooth and compact Al₂O₃-doped NiCrAl coatings.