Friction and Wear Properties of Double Cathode Plasma Sputtering Deposited NbTiN₂ Coating on TC4 Alloy Surface

NbTiN₂ coating was prepared on TC4 alloy surface by dual cathode plasma sputtering deposition. The phase composition, microstructure, hardness, adhesion to matrix and friction and wear properties of the coating were studied. The results show that the NbTiN₂ coating had strong (220) preferred orientation. The coating had good surface quality, no obvious defects and a thickness of about 10 μm. The average hardness of the coating was 2 478.46 HV, about 6 times that of the matrix, and the critical load of coating in scratch test was 68.5 N, indicating that the coating was well combined with the matrix. The friction coefficient of the coating was lower than that of the matrix under the load of 2-5 N at room temperature; the wear scar was narrower than that of the matrix, and the wear rate of the coating was one order of magnitude lower than that of the matrix; the main wear mechanism of the coating was fatigue wear. At 500 ℃, the friction coefficient was higher than that at room temperature, and the wear scar of the coating was narrower and shallower; the wear rate was lower, and the wear mechanism was adhesive wear and oxidation wear, indicating the coating had better wear resistance.