Abstract
Co-based superalloys in the past have worse oxidation resistance since the addition of Cr has bad influence on γ′ stability. Furthermore, the protective Cr2O3 layer is tends to volatilize at high temperature. Two sets of Co-based alloys were investigated in this study in order to enhance the high temperature corrosion resistance. One is the modification of composition based on the commercial UMCO50; the other set is γ′-bearing Co-Al-W-Ni-Si alloy system. Experimental works include microstructure analysis, thermal property, mechanical properties like hardness and erosion. Moreover, isothermal oxidation at 900°C, 1000°C, 1100°C, and 1150°C and hot corrosion at 900°C were conducted to observe the surface stability by adding the oxide-forming elements like Al and Si. The results indicated that the continuous Al2O3 protective layer formed by addition of Al or Si can have an improvement on the materials’ high temperature surface stability, i.e. lower down the weight gain condition. Moreover, lower W content can enhance material’s ability of forming Al2O3 protective layer at high temperature as well. Pre-oxidation treatment can also make the alloys have outstanding performance. In the aspect of hot corrosion, alloys studied here were many times better than commercial UMCO50. As the result, these type newly developed Co-based alloys may have the potential for high temperature applications.