CALPHAD技术在Co基粘结层合金制备中的应用

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

摘要:

利用CALPHAD方法预测了Co基粘结层合金元素对相组成的影响,计算结果表明：Al对β`和γ相的析出量影响显著,Cr对σ相的析出量影响显著,从而确定了Al和Cr元素合适的成分范围分别于13%和22%附近。在此基础上计算了设计成分合金的相组成随温度的变化规律,结果表明：合金于1 208 ℃开始从基体β`相中析出γ相,974 ℃时,γ含量达到最高,随后将析出脆性的σ相。依据此相转变规律建议给出了合金的热处理工艺,1 300 ℃固溶,结合1 000 ℃时效处理。采用真空感应熔炼制备合金样品,铸态合金经上述热处理后得到β`+γ的两相组织,合金元素的偏析明显改善,非晶组织基本消除,得到较为理想的热障涂层粘结层用Co基合金靶材。

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.