论文部分内容阅读
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M_6C碳化物析出的影响。结果表明,热压缩变形后M_6C碳化物含量明显增加;成分分析显示晶界中的M_6C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M_6C比富铬的M_(23)C_6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M_6C在晶界中的析出速率。
The effect of hot compressive deformation on the grain boundary segregation and the precipitation of M_6C carbides in Ni-20Cr-18W-1Mo superalloy was investigated by means of thermal simulator, scanning electron microscopy (SEM) and X-ray diffraction (XRD) The results show that the content of M_6C carbides obviously increases after hot compression deformation. The compositional analysis shows that the M_6C carbides in the grain boundaries contain high content of tungsten. At the same time, the size of the secondary carbides in the grain boundaries after 3% deformation is 3 ~ 5μm, while the size of the secondary carbides in the un-deformed alloys aged at 900 and 1000 ° C is less than 1μm. According to the results of thermodynamic calculations, the Gibbs free energy of the γ matrix phase and the carbide decreases with the increase of the deformation temperature, and the tungsten rich M_6C is more stable than the chromium-rich M_ (23) C_6. Comparing with the experimental results, it is found that the compressive stress accelerates the segregation rate of tungsten in the grain boundary region and further increases the precipitation rate of M_6C in the grain boundary.