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采用电镜分析为主要手段并结合相应的力学性能作为强化和脆化的评判特征,以研究当今世界上最广泛应用的高温合金INCONEL718在高温长期时效过程中的相转变规律为出发点,以分析合金组织失稳的本质为依据,为发展新一代高组织稳定性的改型合金提出方向。 将合金在593～704℃的广宽温度范围内进行1000～50000h的长期时效。研究结果表明,合金强化失效不仅在于主要强化相γ″和γ′的聚集长大,以及γ″向稳定的δ相的转变,而且晶界σ相的析出是合金脆化的主要原因。 选用实际运行了28000h从齿顶到齿根具有温度梯度(为650～450℃)的涡轮盘榫齿作为高温长期应力时效下的试验分析材料。提出了应力明显诱发合金中的γ″ δ相变过程,并认为γ″ δ相的转变是高温长期使用过程中组织失稳而导致强化程度减弱的主要原因。同时完整地阐述了INCONEL718合金中γ″ δ的相变机制,提出了这种相变的模型。 在了解了合金失稳的本质的基础上,对合宜地调整主要强化元素Nb、Ti和Al的含量及比例,以企提高组织稳定性等进行了系统的研究。最后,提出了改型合金含后发展的方向及高组织稳定性改型合金的最佳成分范围。
Electron microscopy (SEM) analysis was taken as the main method and combined with the corresponding mechanical properties as the evaluation features of strengthening and embrittlement. Based on the study of the phase transition law of INCONEL718, the most widely used superalloy in the world at long-term aging at high temperature, The basis of instability is the basis for the development of a new generation of high stability of the modified alloy proposed the direction. The alloy was aged at a temperature of 593 ~ 704 ℃ for a long time of 1000 ~ 50000h. The results show that the failure of alloy strengthening is not only due to the aggregation and growth of γ ’’ and γ ’, but also the transition from γ’ to stable δ phase. The precipitation of σ phase in the grain boundary is the main reason for alloy embrittlement. Select the actual operation of the 28000h from the top of the tooth root to the root of the temperature gradient (650 ~ 450 ℃) of the turbine disk tenon teeth as a test material under high temperature long-term stress aging. It is proposed that the γ “δ phase transformation in the alloy is obviously induced by the stress. It is considered that the transformation of γ” δ phase is the main reason for the weakening of the structure due to the instability of the structure during long-term use at high temperature. At the same time, the phase transition mechanism of γ "δ in INCONEL718 alloy is fully described and a model of this phase transition is proposed.On the basis of understanding the nature of the instability of the alloy, it is necessary to properly adjust the main strengthening elements Nb, Ti and Al Content and proportion, with the enterprise to improve the stability of the system conducted a systematic study.Finally, the modified alloy with the post-development direction and high stability of the modified alloy the best composition range.