恢复热处理对定向合金γ′相再服役稳定性的影响

Effect of rejuvenation heat treatment on re-service aging stability ofγ′phase in directionally solidified superalloy

以原始态和恢复态定向合金为研究对象,通过再服役高温时效和γ′相组织形貌观察,分析原始态和恢复态定向合金γ′相的时效稳定性,研究恢复参数对恢复态定向合金γ′相时效稳定性的影响。结果表明,恢复热处理可将蠕变损伤组织恢复到接近原始态定向合金状态。但相比于原始态定向合金,恢复态定向合金的枝晶干γ′相再服役时效稳定性较差,这与MC碳化物的分解密切相关。不同恢复热处理参数下获得的恢复态定向合金的时效稳定性差异较大。固溶温度越高,保温时间越短,冷却速率越大,恢复态定向合金的枝晶干γ′相时效速率越大;一次时效温度和保温时间越大,恢复态定向合金的枝晶干γ′相时效速率越小。二次时效条件对恢复态定向合金γ′相的时效稳定性无明显影响。

High temperature aging treatment was first conducted on the rejuvenated directionally solidified superalloy to simulate the re-service aging damage of turbine blades and the virgin directionally solidified superalloy respectively.Then re-service aging stability ofγ′phase in the virgin and rejuvenated directionally solidified superalloy was compared and analyzed,and the effect of different rejuvenation parameters onγ′phase microstructure of the rejuvenated directionally solidified superalloy after the same re-service aging time was studied.The results show that although rejuvenation heat treatment can effectively restore creep microstructure to a nearly‘‘as-new’’condition,the re-service aging stability ofγ′phase in the rejuvenated directionally solidified superalloy is worse than that of the virgin directionally solidified superalloy,which is attributed to the decomposition of MC carbide.The rejuvenation heat treatment parameters have a great influence on re-service aging stability of the rejuvenated directionally solidified superalloy.The re-service aging rate ofγ′phase in the rejuvenated directionally solidified superalloy becomes higher,the higher the solution temperature,the shorter the holding time and the greater the cooling rate after solution higher.However,the increased primary aging temperature and holding time cause the decrease of the re-service aging rate ofγ′phase in the rejuvenated directionally solidified superalloy.The second aging condition has no obvious effect on the re-service aging stability ofγ′phase.