采用热模拟试验机、扫描电镜(SEM)和 X 射线衍射仪(XRD)等手段，研究热压缩变形对 Ni?20Cr?18W?1Mo高温合金的元素晶界偏聚和 M6C 碳化物析出的影响。结果表明，热压缩变形后 M6C 碳化物含量明显增加；成分分析显示晶界中的 M6C 碳化物含有高含量的钨元素。同时，经过10%变形后晶界中的二次碳化物尺寸为3~5μm，而经过900和1000°C 时效未变形的合金中晶界二次碳化物尺寸小于1μm。根据热力学计算结果，γ基体相和碳化物的吉布斯自由能随变形温度升高而降低，富钨的 M6C 比富铬的 M23C6稳定。与实验结果比较发现，压应力加速了钨元素在晶界区域的偏聚速率，进一步增加了富钨的 M6C 在晶界中的析出速率。
The effect of hot compression on the grain boundary segregation and precipitation behavior of M6C carbide in the Ni?20Cr?18W?1Mo superalloy was investigated by thermomechanical simulator, scanning electronic microscope (SEM) and X-ray diffraction (XRD). Results indicate that the amount of M6C carbides obviously increases in the experimental alloy after hot compression. Composition analyses reveal that secondary M6C carbides at grain boundaries are highly enriched in tungsten. Meanwhile, the secondary carbide size of compressive samples is 3?5 μm in 10% deformation degree, while the carbide size of undeformed specimens is less than 1 μm under aging treatment at 900 and 1000 °C. According to the thermodynamic calculation results, the Gibbs free energy of γ-matrix and carbides decreases with increase of the compression temperature, and the W-rich M6C carbide is more stable than Cr-rich M23C6. Compared with the experimental results, it is found that compressive stress accelerates the W segregation rate in grain boundary region, and further rises the rapid growth of W-rich M6C as compared with the undeformed one.
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