Application of CALPHAD Method in the Preparation for Co-based Bond Coating Alloys

Abstract:

The effects of alloying elements on phase equilibria in Co-based bond coating alloys are predicted by CALPHAD method. The results show that Al significantly influences on the precipitation amounts of β` and γ, and Cr has a definite effect on the precipitation of σ. The appropriate contents of Al and Cr elements are determined to be around 13% and 22%, respectively. The results of calculated phase formations and phase changes as a function of temperature are extensively discussed, which indicats that γ begins to precipitate from the matrix β` at 1208 ℃ and reaches the highest content at 974 ℃, then the σ will precipitat. According to the phase transformation, the heat treatment process of the alloy was formulated, dissolved at 1300 ℃ and aged at 1 000 ℃. The alloy samples were prepared by vacuum induction melting. Segregation and the amorphous structure in as-cast alloys was eliminated after the above heat treatment, and the two-phase structure, β`+ γ, of the commercial target is obtained.

Key words:CALPHAD; Co-based bond coating alloy; material design; heat treatment