AES INVESTIGATIONS OF THE HOT CRACKING OF AN ELECTRON-BEAM WELDED NICKEL-BASE ALLOY FOR TURBINE DISKS

Electron-beam joints of welded and heat treated specimens of UDIMET 70 0LC often show hot crack. In situ AES investigations of dummy welds of the same material prove accumulations of sulfur on inner surfaces. Th e residual stresses of the welding process reach their highest values exactly in the heat affected zone (HAZ). These stresses in combination with reduced formability are responsable for the formation of microcr acks. AES investigations in combination with hot tensile and creep tes ts indicate that there exists a direct relationship between the fracti on of sulfur covered grain boundaries in the HAZ, the total sulfur con tent of the material and the failure probability of welded specimens.