Microstructures and Antioxidation of W Self-Passivating Alloys: Synergistic Effect of Yttrium and Milling Time

Abstract

Tungsten and its alloys are widely recognized as key components in high-temperature environments. In this study, self-passivating W-Si-xY alloys with varying Y content were prepared using mechanical alloying (MA) and spark plasma sintering (SPS). The synergistic effects of Y content and milling time on the microstructures and oxidation resistance of the alloys were revealed. This study found that the oxidation resistance of the alloys increased as the Y content increased. However, the effect of milling time on oxidation resistance was complex. For W-Si-xY alloys with low Y content (0Y and 2Y), the oxidation resistance decreased with increasing milling time. In contrast, for W-Si-xY alloys with high Y content (4Y and 6Y), the oxidation resistance increased with increasing milling time. This enhanced oxidation resistance is due to the microstructural changes in the protective composite layer, including the size and distribution of W5Si3, Y2Si2O7 aggregates, and W-Y-O melt. The thickness of the oxide layer on the W-Si-6Y alloy after being oxidized at 1000 °C for 2 h was only 70.7 μm, demonstrating its superior oxidation resistance.