| Summary: | Self-passivating W alloys have excellent high temperature oxidation resistance and are expected to be used as a key component in high temperature environment. In this study, a series of W-Si-<i>x</i>Y self-passivating alloys were fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). Effects of Y content on phase compositions, microstructures, and oxidation resistance at high temperatures were investigated systematically. The results show that the oxidation resistance of the alloys increases with the increase of Y content (0.0~5.0 wt.%), but the oxidation resistance of the alloys deteriorates when the Y content reaches 9.6 wt.%. The alloy with 3.8 wt.% Y shows the best oxidation resistance. The thickness of its oxide layer is ~249.1 μm when the oxidation time reaches 80 h, which is thinner than that of other alloys. Effects of Y content on the oxidation resistance are revealed. During the oxidation process, Y can react with other elements to form molten-like W-Y-O and Y<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> particles. It is found that these two phases play a key role in the oxidation resistance of the alloys. When the Y content is in the range of 0~5.0 wt.%, a W-Y-O covering layer gradually forms with the increase of Y content, which can prevent further oxidation of the alloy. In the meantime, small Y<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> particles were formed and the microcracks formed around these particles were isolated, which have little effect on the oxidation resistance of the alloys. However, when Y content reaches 9.6 wt.%, large Y<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> particles and extensive cracks around them are formed. These cracks are interconnected to form penetrating channels for O<sub>2</sub> from the environment to the alloy interior, which deteriorates the oxidation resistance of the alloys.
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