Oxidation of molybdenum-tungsten-chromium-silicon alloys

The oxidation kinetics of (50–60) wt.% Mo-(35–47) wt.% Cr-(2–5) wt.% Si and (30–40) wt.% Mo-(30–40) wt.% W-(27–37) wt.% Cr-(0–3) wt.% Si alloys were studied between 1000 and 1200°C in a pure oxygen atmosphere. The oxidation of Mo-W-Cr-Si alloys resembled that of Mo-Cr-Si alloys but was much more oxidation resistant. In general, oxidation resistance increased with increasing Cr and Si content. Alloys with good oxidation behavior had a thin outer Cr₂O₃ layer and an internal oxidation zone (in both Mo and Mo-W alloys). Alloys displaying poor oxidation behavior had a porous Cr₂O₃ layer (in Mo alloys) or layers of oxides of W and Cr (in Mo-W alloys). Although the alloy systems were not truly oxidation resistant, definite improvement in oxidation resistance was achieved.