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研究了5种不同含量的C对单晶高温合金凝固组织及持久性能的影响.结果表明,随着C含量的增加,共晶数量明显减少,碳化物数量增多,且碳化物主要分布在枝晶间区域,当C含量较高时,在枝晶干上也有少量碳化物出现.经过热处理后,合金的枝晶间粗大的γ/γ′共晶基本消除,枝晶间少量未被固溶掉的γ/γ′共晶,达到了较好的均匀化效果;碳化物形貌比铸态更为简单,尺寸明显减小,体积分数减小,且分布更加弥散,碳化物类型更加丰富,出现了粒状和链状的M23C6碳化物.随C含量增加合金的高温持久寿命先增大后减小,当C含量为0.045%时,高温持久寿命最大.引起持久性能变化的主要原因是由于合金中未消除的共晶、碳化物及缩松的存在,未消除的共晶以及碳化物都是裂纹萌生的位置,而共晶和碳化物的数量随着C含量的增大又呈相反的变化趋势,因此C的加入要适量.
The effects of five different contents of C on the microstructure and ductility of single crystal superalloy were investigated. The results show that with the increase of C content, the amount of eutectic obviously decreases and the amount of carbides increases. The carbides mainly distribute in dendrites In the intergranular region, a small amount of carbides appeared on the dendrites when the C content was higher, and the coarse γ / γ ’eutectic between the dendrites was basically eliminated after the heat treatment, and a small amount of the interdendrites were not dissolved Of γ / γ ’eutectic, to achieve a better homogenization effect; carbide morphology than the as-cast is more simple, significantly reduced in size, volume fraction decreases, and the distribution is more dispersed, the type of carbide is more abundant, the emergence of Granular and chain M23C6 carbides.With the increase of C content, the high temperature long-life of the alloy first increases and then decreases, and when the C content is 0.045%, the high temperature long-term life is the largest.The main reason for the change of long-term performance is that in the alloy Un-eliminated eutectics, the presence of carbides and shrinkage, undisturbed eutectics, and carbides are the sites of crack initiation, while the number of eutectics and carbides is inversely changing as C content increases , So C should be added to the right amount.