抄録
W-Cr sintered alloys (up to 30%Cr) containing 0.2-1.0% of palladium were produced from W-Cr alloyed powders and subjected to the oxidation at the temperatures, 1200°C and 1300°C in air. The effect of palladium-addition on the oxidation characteristics of these alloys was examined as a function of chromium content, and the protection mechanism to the oxidation was also examined.
The results were summarized as follows:
1) The oxidation characteristics of W-Cr sintered alloys was markedly influenced by the small addition of palladium. The alloy of W-9.87%Cr-0.2%Pd, for example, failed catastrophically in 2 hrs, while the alloys of W-9.87%Cr-0.41.0%Pd resisted over 1000 hrs to the oxidation at 1300°C in air.
2) The more chromium content increased, the more amount of palladium was required for improving the oxidation resistance of these alloys.
3) The improvement of oxidation resistance in W-Cr-Pd alloys owes the a-Pd phase which precipitates pre-ferentially in the vicinity of grain boundaries. This phase shows not only good oxidation resistance, but also contributes to the formation of the protective Cr2O3 surface layers.
