Heat affected zone liquation cracking in electron beam welded third generation nickel base superalloys

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 476; no. 1; pp. 217 - 223
• Main Authors: Ojo, O.A., Wang, Y.L., Chaturvedi, M.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-03-2008; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; Heat affected zone cracking; Joining; Joining, thermal cutting: metallurgical aspects; Metals. Metallurgy; Superalloy; Welding; Superalloy; Heat affected zone cracking; Joining; Welding; Nickel base alloys; Directional solidification; Tantalum alloy; Intergranular cracking; Cast alloy; Inorganic compound; Dendrite; Optical microscopy; Electron beam welding; Carbon addition; Hafnium alloy; Transition metal alloy; Eutectic transformation; Heat affected zone; Microstructure; Weldability; Microsegregation
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2007.04.091

The weldability of directionally solidified nickel base superalloy TMS-75 and TMS-75+C was investigated by autogenous bead-on-plate electron beam welding. The analysis of microsegregation that occurred during solidification of the as-cast alloys indicated that while W and Re segregated into the γ dendrites of both the alloys, Ta, Hf and C were rejected into the interdendritic liquid in the TMS-75+C. Heat affected zone intergranular liquation cracking was observed in both the materials and was observed to be closely associated with liquated γ–γ′ eutectic microconstituent. The TMS-75+C alloy, however, exhibited a reduced extent of HAZ cracking compared to TMS-75. Suppression of terminal solidification reaction involving non-invariant γ–γ′ eutectic transformation due to modification of primary solidification path by carbon addition is suggested to be an important factor contributing to reduced susceptibility of TMS-75+C alloy to HAZ liquation cracking relative to the TMS-75 superalloy.