Effect of aluminum addition on microstructure, mechanical properties and high temperature tribological properties of nickel-rich NiTi alloy

The nickel-rich 60NiTi alloy with high strength, excellent corrosion resistance and low elastic modulus, is ex-pected to be the next generation of bearings in aerospace applications. However, it needed the heat treatment to enhance its hardness, and the poor performance in wear and oxidation resistance at higher temperatures also limit its wide application. In this study, the effects of Hf and Al on the microstructure, mechanical properties, high-temperature tribological properties and oxidation resistance of 60Ni-40Ti alloys were studied. The results showed the Al addition reduced the precipitation of the second phases such as Ni3Ti and Ni3Ti2 in the matrix, and formed the new NiTi2, which helped improve the microhardness of the alloy. Tribological results proved that the 54Ni-40Ti-3Hf-3Al alloy obtained better tribological performance in almost all test conditions than 60NiTi and 57Ni-40Ti-3Hf, this was attributed to the formation of the dense and stable oxide glaze layer on the wear surface. The wear mechanism transitioned from abrasive wear and adhesive wear at room temperature to oxidation wear and delamination wear at 300 degrees C. This work provided a method to improve the wear resistance of 60NiTi alloy at high temperature.

Automated summary

This study investigated the effects of Hf and Al on the properties of 60Ni-40Ti alloy. The addition of Al reduced the precipitation of second phases and improved the microhardness of the alloy. The 54Ni-40Ti-3Hf-3Al alloy showed better tribological performance and formed a stable oxide glaze layer at high temperatures. This research provides a method to enhance the wear resistance of 60NiTi alloy at high temperatures.