A study of linear friction weld microstructure in single crystal CMSX-486 superalloy

The microstructure of linear friction welds in single crystal (SX) CMSX 486 superalloy was studied. Gleeble thermomechanical simulation of the welding process was also performed in order to understand the microstructural changes induced in the alloy during the joining process. Microstructural analysis of the welded and Gleeble-simulated specimens showed that extensive liquation occurred in the alloy during joining, which is in contrast to the general assumption that linear friction welding (LFW) occurs exclusively in the solid state. The study revealed the application of the compressive load during the forging stage of LFW induced rapid solidification of the resultant metastable liquid phase. Nevertheless, part of the liquid resulted in a continuous Hf-base oxide phase along the weld line. Possible ways of preventing the formation of the potentially deleterious oxide film and, thus, improve the prospect of applying LFW for the joining of CMSX-486 superalloy are suggested.Peer reviewed: YesNRC publication: Ye