Induction-assisted laser welding of IN-738 nickel-base superalloy

Induction-assisted laser welding was performed with filler metal additions to weld IN-136, a nickel-base superalloy. IN-738 powder was added through a coaxial nozzle to the weld pool in order to reduce the weld defects, such as underfill and porosity in the welds. This was particularly important for the square-groove butt joints due to the presence and opening of gaps in the welding process. Crack-free laser welds were obtained by induction preheating at approximately 800 degrees C, however, some scattered pores were still observed in the welded specimen. Tensile testing indicated that the strength of the weld metal was comparable to that of the base metal at 850 degrees C. Stress-induced precipitation of fine gamma' particles was also observed on IN-738 specimens subjected to tensile loading. The preliminary results of this study demonstrated that the quality and performance of laser-welded IN-738 specimens were acceptable. However, more works on the process optimization are required to further improve the weld quality. (C) 2008 Elsevier B.V. All rights reserved.