| In order to improve the hardness and wear resistance of 2024 Al alloy, a new way of producing duplex coatings consisting of two steps was carried out. First, a Ti film was deposited on 2024 Al alloy substrate by closed field unbalanced magnetron sputtering, Then, this pre-coated substrate was plasma nitrocarburized. The morphology, phase structure and elements distribution in Ti film and duplex layer were characterized by a series of observation and analysis of OM, SEM, XRD and EDS. Additionally, the microhardness profile, wear resistance of the layer were also measured by microhardness, nano indention and wear test.The OM, SEM observation and XRD analysis results show that the surface of as-deposited Ti film is smooth and the phase structure is hexagonal and has a (002) preferred orientation. The morphology of pre-coated substrate become rough and the content of N are high in the surface. The duplex layer consists mainly of phase TiN, Al18Ti2Mg3 and Al3Ti. With the increasing of the nitriding temperature and time, the content of Al18Ti2Mg3 and Al3Ti phase increase. There is a strong interdiffusion between Ti film and substrate. Moreover, N has a high content in the outside layer and Mg segregates in the inner layer near Al substrate. With increasing temperature and time, the diffusion progress become evident and the thickness of layer increase. The hard test results show that the hardness and elastic modulus of duplex coatings highly improved compared with substrate. After 4h nitriding at 460?C in N-H ratio of 0.1:0.3, the hardness can reach HV0.011158 with the distance from surface 5μm. The nano hardness can reach 12.374GPa and the elastic modulus can reach 211.73GPa in the area near surface after nitriding the substrate with a 4.8μm Ti film. The wear rate of 2024 Al alloy decrease after duplex treatment, and the friction coefficient has a slightly decrease. The wear rate of as-treated susbtrate with 6.33μm Ti film deceased by 64.7% compared with the untreated substrate.
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