一种单晶镍基合金热处理制度的研究

Study on heat treatment conditions of single crystal nickel-based superalloy

通过对一种单晶镍基合金的差热曲线分析和不同条件热处理后的组织形貌观察，制定合金热处理工艺，并研究了热处理期间γ′相的组织演化规律．结果表明，实验用合金的热处理“窗口”是1272～1320℃，在1300℃时，γ′相有最大的溶解速度，1040℃析出的γ′相最为稳定，在该温度时效50h后。γ′相长大，且呈球状和条状形貌，γ′/γ两相之间出现界面位错．因此，确定出该合金的热处理工艺为1280℃，4h,A．C＋1300℃，4h，A．C＋1040℃，4h，A．C＋870℃，24h。A．C．一次时效促使γ′相长大呈立方体形貌；二次时效期间，γ′相略有长大，立方度增加，排列更加规则．

The regularity of microstructure evolution for a single crystal nickel-base superalloy during heat treatment had been investigated by means of the analysis on the differential thermal curve （DTA） and observation on microstructure. Results show that ＂window＂ of heat treatment for the experimental superalloy is detected to be 1 272-1 320 ℃. There is a maximal solution rate of γ′ phase at about 1 300 ℃, and a better stability of the γ′ phase precipitated at about 1 040 ℃. However, as the time of ageing treatment is prolonged to 50 h at 1 040 ℃, the γ′ phase in the alloy grows into the morphology of the sphere-like and strip-like, and the interracial dislocations develop between γ′ and γ phases. Therefore, heat treatment conditions of the alloy is determined as 1 280 ℃, 4 h, A. C ＋ 1 300℃, 4 h, A. C ＋ 1 040 ℃, 4 h, A. C ＋ 870 ℃, 24 h, A.C. In the role of the interface and lattice misfit strain energies, the γ′ phase has grown and possesses cubic shape during first ageing at 1 040 ℃. After second ageing, the cubic γ′ phase has slightly grown into the form of the regular arrangement, and the cubic degree of the γ′ phase increases.