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采用OM,SEM和TEM等手段,分析了Nb/Ti比对铸造镍基高温合金长期时效微观组织演化的影响.结果表明,在长期时效期间,Nb/Ti比对g’相形貌演化和粗化影响不大,但对g’相体积分数有一定影响.初生MC中Nb/Ti比和(Nb+Ti)/(W+Mo)比与合金Nb/Ti比具有很好的线性关系.随合金Nb/Ti比下降,2个比值线性下降,使MC分解程度提高,热稳定性降低;但是,2个比值的显著改变并不能导致MC分解程度的大幅变化,还存在其它因素对MC热稳定性具有重要影响.MC的分解程度可通过分解前后体积分数的变化来计算,而热稳定性强弱则可由分解程度来定量表达.Nb/Ti比降低,晶界粗化更加严重,晶界析出M23C6的倾向增大,析出M6C的倾向减小.但是,合金中m相的析出演化行为并未受到Nb/Ti比的明显影响.
The effect of Nb / Ti ratio on the microstructure evolution of cast Ni-base superalloy was investigated by means of OM, SEM and TEM. The results show that during the long-term aging, Has little effect on the phase volume fraction of g ’, but the ratio of Nb / Ti to (Nb + Ti) / (W + Mo) in the primary MC has a good linear relationship with the Nb / Ti ratio of the alloy The Nb / Ti ratio decreased and the two ratios decreased linearly, which led to the increase of MC decomposition and the decrease of thermal stability. However, significant changes in the two ratios did not lead to large changes in MC decomposition, The degree of decomposition of MC can be calculated by the change of the volume fraction before and after decomposition, while the thermal stability can be quantitatively expressed by the degree of decomposition.Nb / Ti ratio is reduced, the grain boundary coarsening is more serious, grain boundary precipitation The tendency of M23C6 increases and the tendency of precipitation of M6C decreases.However, the precipitation behavior of m-phase in the alloy is not affected obviously by the Nb / Ti ratio.