Effect of Y Content on Tribological Properties in Wide Temperature Range of Ni-Mo-Y Alloy

The Ni-Mo-Y alloy with different Y content (0, 0.5%, 1.5%, 2.5%) was prepared by powder metallurgy hot pressing Sintering. The microstructure, phase composition, mechanical properties and friction and wear properties at different temperatures (room temperature, 200, 400, 600, 800 ℃) were studied by optical microscope, scanning electron microscope, X-ray diffractometer, Raman spectrometer and high temperature friction tester. The results show that the Ni-Mo-Y alloy with different Y content was mainly composed of austenite, and had uniform and dense microstructures. With the increase of Y content, the grain of the alloy was refined, twins formed, precipitated phase number increased, the density decreased, and the hardness and yield strength increased and the increased rate slowed down. When the Y mass fraction was 1.5%, the refining and modification effects were the best. With the increase of friction temperature in the range of room temperature to 400 ℃, the lubricating nickel-molybdenum oxides and a small amount of molybdate were formed on the friction surface of Ni-Mo-Y alloy with Y content 1.5%, which were incomplete covering the surface, the friction factor decreased, but the volume wear rate increased due to abrasive wear. When the friction temperature rose to 600,800 ℃, the lubricating, completely dense nickel-molybdenum oxide and molybdate film was formed on the friction surface gradually, which completely covered the surface, and the friction factor and volume wear rate decreased significantly. The Ni-Mo-Y alloy had good friction and wear properties at high temperature.