Improvement of Oxidation Resistance in Tungsten Heavy Alloys through Si, Y2O3, Ni, and Co Addition

Self-passivating tungsten heavy alloys are important due to their high melting point, strong mechanical properties, and good oxidation resistance. Powder metallurgy is a key process in the preparation of these alloys, where it allows for precise control over composition and the inclusion of alloying elements. In the present study, we aim to evaluate the effect of alloying elements on the oxidation resistance of W-1Si-0.3Y(2)O(3,) W-10Ni-3Co-0.3Y(2)O(3) and W-10Ni-3Co-1Si-0.3Y(2)O(3) alloys fabricated by mechanical alloying followed by conventional pressureless sintering. The isothermal oxidation behaviour of synthesized alloys was conducted at 800, 1000 and 1200 degrees C up to 10 h to study oxide growth kinetics, phase and microstructure evolution. The addition of 1 wt.% Si into tungsten produces fine SiO2 particles on tungsten oxide grain boundaries during oxidation, which effectively prevents WO3 grain growth and crack propagation. However, low Si content results in a lack of continuous oxide layer, leading to WO3 volatilization. In contrast, alloys W-10Ni-1Si-0.3Y(2)O(3) and W-10Ni-3Co-1Si-0.3Y(2)O(3) exhibit enhanced oxidation resistance due to the formation of a dense NiWO4/CoWO4 layer beneath the porous WO3 + SiO2 layer. The resistance of tungsten to oxidation was significantly increased through the addition of Si, Y2O3, Ni and Co.