Effect of cobalt on chemical segregation and solution process in Re-containing single crystal superalloys
(1.辽宁省沈阳市科学院金属研究所
2.北京市科学院研究生院
3.Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
4.Institute of Metal Research, The Chinese Academy of Sciences, Shenyang 110016, China)
2.北京市科学院研究生院
3.Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
4.Institute of Metal Research, The Chinese Academy of Sciences, Shenyang 110016, China)
Abstract: The effect of cobalt on chemical segregation and solution process in three nickel base single crystal superalloys was investigated. Three alloys containing the mass fraction of cobalt of 12% (named Alloy 1), 3% (named Alloy 2) and 0 (named Alloy 3), respectively were studied, in which the contents of other elements were same. The results show that the segregation extent of W, Re, Ta, Al between dendrite and interdendritic region rises with the increase of cobalt content. The incipient melting points decrease by 10 ℃ and 20 ℃ respectively when the content of cobalt increases from 0 through 3% to 12%. During solid solution at 1 340 ℃, the solid solution of large gamma prime in interdendritic region and the dissolution of eutectic in alloy 1 become easier than in other two alloys. After heat-treatment at 1 340 ℃ for 8 h, the segregation extent of elements in alloy 1 decreases dramatically, while in alloy 2 and alloy 3, the segregation ratios decrease slowly. It suggests that the higher content of cobalt can accelerate the diffusion process at high temperature.
Key words: single crystal superalloy; cobalt; chemical segregation