STRESS RUPTURE BEHAVIOR OF SUPERALLOY-718 ELECTRON-BEAM WELDMENTS

12mm thick plates of superalloy 718 in solution treated condition were electron beam welded and the weldments, after suitable heat treatment s, were subjected to stress rupture testing at 923 K and 690 MPa Failu re in the transverse specimens always occurred in the base metal indic ating that the weldment had superior stress rupture resistance. This i s attributed to the columnar grain structure of the electron beam weld metal favourably oriented in the direction of stress axis and the min imal segregation in the interdendritic regions of the weld metal due t o fast weld cooling rates associated with electron beam welding proces s.