Effect of Al₂O₃-Content on Microstructures and Tribological Properties of 2219 Al-Alloy Modified with Plasma Sprayed Ni-Coatings

The surfaces of 2219 Al-alloy,an advanced material in lightweight design of structural parts in automotive and aircraft industries,were modified with the Al₂O₃-doped Ni-coatings deposited by plasma spraying of Ni and Al₂O₃ micron powders.The influence of the Al₂O₃-content on the microstructure and tribological behavior of the coating was experimentally studied with X-ray diffraction,scanning electron and conventional mechanical tools The results show that the Al₂O₃-doping had a major impact.Specifically,the Al₂O₃-doping significantly increased the hardness up to 3 times higher than that of the substrate at most; as the Al₂O₃-content increased from 15% to 40%,the hardness increased,accompanied by the decreases of both the wear-rate and friction coefficient,possibly because the “black-spot” area,mainly comprising Al and Al₂O₃,considerably increased.In addition,the oxidative wear was found to be responsible for the wear mechanism.