Effects of Micro-arc Oxidation/Multi-arc Ion Plating Composite Treatment on Microstructure and Properties of TC4 Titanium Alloy

TC4 titanium alloy was treated by micro-arc oxidation (MAO) technology, and then CrN coating was prepared on the surface of MAO coating by multi-arc ion plating (MAIP) technology to form MAO/CrN composite film, so as to improve the tribological properties of TC4. The microstructure and phase composition of the film were detected and analyzed by scanning electron microscopy (SEM) and x-ray diffraction (XRD). The surface roughness, bonding strength and tribological properties of the film were evaluated by using a roughness tester, an automatic scratch tester for coating adhesion, a multi-functional friction and wear tester and a three-dimensional ultra-depth-of-field microscope system. The results show that the tribological properties of TC4 are improved after micro-arc oxidation treatment. The friction coefficient of TC4 is about 0.6, the friction coefficient of TC4/MAO is about 0.5, and the friction coefficient of TC4/MAO/CrN is about 0.2. The surface roughness of TC4/MAO/CrN is only 1.4 mu m. The composite layer exhibits excellent tribological properties. The wear mechanism of TC4, TC4/MAO coating and TC4/MAO/CrN coating is abrasive wear.