Abstract: A newly developed ZMLMC directional solidification apparatus with superhigh temperature gradient has been used in the research of solidification morphologies and microsegregation of directionally solidified K10 superalloy and their relations to the solidification parameters at medium cooling condition. The results show that the microstructures of directionally solidified K10 superalloy at medium cooling condition are highlyrefined with the primary dendzite spacing smaller than one fifth of that by conventional HRS directional solidification process and the growth of sidebranches being intoasely restrained. Moreover the segregation ratios of alloy elements Cr, Mo and Ni tend to unity with the increase of cooling rate from 30K/s to 70K/s. Deadritic segregation has been greatly suppressed or even eliminated.

Key words: 定向凝固, 高温合金, 枝晶偏析, crack propagation, Fatigue pitting, gear, wear debris