The Co-base powder of refractory alloy is drycrushed. The alloy was modified by adding either 2 percentY_2O_3 or 2 percent Al or both. This powder mixture wasconsolidated by hot extrusion, at 1150 deg C and 1250 deg C. allthe variants-previously crushed and consolidated-had fine,scattered, oxide particles. These particles had been stable up to1250 deg C. some tests were performed in view to obtain moreelongated grains-grains containing Y_2O_3,-by heating thepowders up to higher temperatures. The authors could not reachthe necessary recrystallization temperature without the appearanceof a carbide eutectic in melted phase and consequently of someporosity. Such a structural instability results in the limitation ofthe hardening of Co-base refractory alloys using concomitantlycarbides and oxide dispersed particles. All the alloying additionsgreatly improve the oxidation resistance of Co-Cr-Ni-W-C-O alloy, at 1100 deg C.
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