A Study on Hot Ductility Behavior of Ni-based Superalloys

Lee, Choung-Rae; Um, Sang-Ho; Kim, Sung-Wook; Choi, Cheol; Lee, Chang-Hee

Journal of KWJS 2004;22(2):59-68.
Published online September 15, 2004.

A Study on Hot Ductility Behavior of Ni-based Superalloys

Choung-Rae Lee, Sang-Ho Um, Sung-Wook Kim, Cheol Choi, Chang-Hee Lee

Abstract

Plasma transferred are welding (PTAW) has been taken into consideration for repairing Ni-based super alloy components used gas turbine blades. Various cracks has been generally reported to be found in the base metal heat affected zone(HAZ) along grain boundary. Thus, hot cracking susceptibility of Ni-based super alloy was evaluated according to heat treatments. Hot ductility test was conducted on specimens with solution treated at 1120˚C for 2hours and aging treated at 845˚C for 24hours after solution treatment. The results of the hot ductility test appeared that solution treated specimens were the highest ductility recovery rate among three conditions. The loss of ductility at high temperature in Ni-based super alloy was mainly controlled by the degree of grain boundary wetting due to constitutional liquation of MC carbide precipitates. Meanwhile, the highest ductility recovery rate in solution-treated alloys seems to be lack of M23C6, which can be dissolved during heating and then result in the local enrichment of Cr in the vicinity of grain boundary.