Influence of plasma nitriding temperature on microstructures and mechanical properties of Ti-N/Ti-Al multilayer coatings on the surface of 5083 Al alloys

Novel Ti-N/Ti-Al based compound layers were produced on the surface of 5083 Al alloys by duplex surface treatment. Samples were deposited with pure Ti film by using magnetron sputtering and then plasma nitrided for 8 h at 400 °C, 430 °C, 460 °C and 490 °C, in a gas mixture of 40% N₂ + 60% H₂. The treated samples were characterized by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), microhardness tester and pin-on-disc tribometer. Results showed that the duplex layer was composed of the outer TiN_0.3 layer and inner Al₁₈Ti₂Mg₃ layer. The preferred (002) orientation of TiN_0.3 was enhanced with the elevated nitriding temperature. The surface hardness of 5083 Al alloy was remarkably improved by the duplex layer, reaching a maximum value of 900 HV_0.01, which was about 10 times higher than untreated 5083 Al alloy. Significant decrease in friction coefficient and wear rate also occurred for the nitrided samples. The wear mechanism of nitrided samples is dominated by abrasive wear.