喷砂对定向凝固4777DS高温合金再结晶影响及其机理研究

Effect of Sandblasting on Recrystallization Defects of Directional Solidification 4777DS Superalloys and Its Mechanism

摘要:

采用光学显微镜、扫描电子显微镜研究了不同喷砂工艺对4777DS合金再结晶缺陷的影响以及合金产生再结晶的情况。对喷砂的合金表面再结晶组织分析结果表明，随着喷砂强度增加、时间延长、砾径增加以及喷砂距离的减少，合金表面再结晶的深度增加。经喷砂后的变形试样，接近喷砂表面的γ′相由蝶状变成长条状，部分变形γ′相环绕在变形较大的区域，同时由TEM可观察到在γ基体通道与γ′相中分布着大量位错。枝晶干与枝晶间不同的γ′相会影响再结晶的生长，从而使再结晶晶界形成波浪状形貌，未发现共晶及碳化物对再结晶的抑制作用。由于表层再结晶晶粒较小及残存应力的存在，次表层会形成新一层的再结晶晶粒。

Abstract:

The effects of different sand blasting processes on recrystallization defects and the occurrence of recrystallization in 4777DS alloy were studied using optical microscope and scanning electron microscope. The analysis of the recrystallization structure on the alloy surface after sandblasting shows that the depth of recrystallization on the alloy surface increases with the increase in sandblasting intensity, time, and gravel diameter, and the decrease in sandblasting distance. After sandblasting, the deformed sample shows that the γ′ phase near the sandblasted surface changes from a butterfly shape to a long strip shape, and some of the deformed γ′ phase surrounds the areas with greater deformation. At the same time, a large number of dislocations distributed in the γ matrix channels and γ′ phase are observed by TEM. The different γ′ phases between dendrites affect the growth of recrystallization, resulting in the formation of wavy grain boundaries. No inhibitory effect of eutectic or carbide on recrystallization has been found. Due to the small size of surface recrystallized grains and the presence of residual stress, a new layer of recrystallized grains will form in the subsurface.