Exceptional Low Temperature Fabrication of Self-Passivating Tungsten Alloys by Mechanical Alloying and Spark Plasma Sintering

Abstract

The present research reports exceptional low temperature fabrication of yttria-free and yttria-dispersed W-Ni-Co-Si alloys by mechanical alloying (MA) and spark plasma sintering (SPS). In this work, three different alloys, W-1Si-0.3Y2O3 (WSY), W-10Ni-3Co-1Si (WNCS), and W-10Ni-3Co-1Si-0.3Y2O3 (WNCSY), were synthesized using MA and SPS. The densification behavior, phase evolution, microstructural development, hardness and oxidation resistance of these alloys were investigated. It was found that the WNCS and WNCSY alloys exhibited high relative densities of 94 and 96% and hardness of 6.1 and 6.7 GPa, respectively, even at lower sintering temperature of 1300 °C, while the WSY alloy had a relatively low density of 67% and hardness of 4.1 GPa. After performing oxidation study of these alloys at 1000 °C, WSY showed resistance to oxidation by forming fine SiO2 particle on the surface

however, crack initiation was observed after 10 h. In contrast, WNCS and WNCSY alloys demonstrated better oxidation resistance due to the presence of NiWO4 and SiO2 particles in addition to WO3 grains on the surface. The addition of Y2O3 in WNCSY showed enhanced oxidation resistance by reducing ion migration through the oxide scale during oxidation. Overall, this research provides valuable insights into the design and development of self-passivating tungsten alloys for high-temperature applications. © ASM International 2024.