摘 要：采用螺旋选晶法制备镍基单晶高温合金，研究了2%，3%，4%(质量分数)三种成分Mo含量对合金显微组织和高温持久性能的影响。结果表明： 3种成分合金铸态组织均由γ，γ′相组成。热处理后，4%Mo合金开始有μ相析出。1100℃,500h热暴露后，4%Mo合金中的μ相大量析出并长大，3%Mo合金中只有少量μ相析出，2%Mo合金中不析出μ相。析出的μ相主要由Mo、Re、W、Cr、Co和Nb等元素组成，其中Mo形成μ相倾向最强，Re、W和Cr次之，Nb和Co最小。大量棒状μ相的析出严重损害了合金的高温持久性能，少量μ相不降低合金的高温持久性能，反而因Mo的固溶强化作用使合金高温持久性能升高。对于Ni-5Cr-10Co- 4W-3Re-5.6Al-8Ta-1Ti-0.5Nb基础成分合金，最佳的Mo含量为3wt.%。
Abstract: Ni-base single crystal superalloys were prepared by screw selecting method. And the effects on microstructures and stress rupture properties of three kinds of Mo content superalloys with 2%, 3%, 4% were investigated, separately. The results showed that three as-cast structures of the alloys were composed of γ and γ′ phases. After heat treatment, alloy with 4% Mo content began to precipitate µ phase. The µ phase of alloy with 4% Mo content precipitated abundantly and grew, while alloy with 3% Mo content only a few µ phase and 2% Mo content without µ phase after heat exposure at 1100℃/500h. The µ phase was mainly composed of element Mo, Re, W, Cr, Co, Nb etc., in which the tendency of forming µ phase of Mo was the strongest, Re, W ,Cr took the second place and Co, Nb was the weakest. A lot of precipitation of stick-shaped µ phases damaged high temperature stress rupture properties of alloys. A few µ phase didn’t decrease high temperature stress rupture properties of alloys, on the contrary, improved them due to the solid solution strengthening effect of Mo. Therefore, the optimum Mo content should be 3wt.% for the based composition alloy Ni-5Cr-10Co-4W-3Re-5.6Al-8Ta-1Ti-0.5Nb.
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