Effect of Trace Ag on Tribological Properties of TiAlN coating

TiAlN and TiAlAgN coatings with different Ag contents were prepared by arc ion plating with Ti₅₀Al₅₀, Ti₅₀Al₄₉Ag₁, Ti₅₀Al₄₅Ag₅ alloy targets in this paper. The tribological properties were studied by using a ball-on-disk tribo-meter at room temperature, 200 ℃, 400 ℃ and 600 ℃.The surface morphology, microstructure, hardness and adhesion of the coatings before and after wear were determined by scanning electron microscope, X-ray diffraction, microhardness tester, surface profiler and scratch tester. The results showed that the thickness of TiAlN, TiAlAgN(0.12%Ag, atomic percentage), TiAlAgN(0.30%Ag, atomic percentage) coating was 4.18 μm, 5.31 μm and 4.69 μm. The hardness was HV_0.2 2 049.4, HV_0.2 1 672.9, HV_0.2 1 398.5, respectively. The diffraction peaks of TiAlN and TiAlAgN coatings were the same as those of FCC TiN, and the preferential orientation of N(220) for TiAlN coating was found after adding Ag. The wear mechanism of the three coatings at elevated temperatures was identified as adhesive wear and abrasive wear. At room temperature, the friction coefficient of TiAlN coating was about 0.3, which was lower than that of the other two coatings. The wear rate of the three coatings was higher at 200 ℃, and the best wear resistance was obtained at 400 ℃. In addition, as the Ag contents were between 0.12%~0.30%, the adhesion of the coating decreased.