Linear friction welding of Allvac® 718 plus superalloy

Linear Friction Welding (LFW) process was used to join Allvac718 Plus (718 Plus) superalloy and produce a sound weld that was free of cracks both after welding and post weld heat treatment (PWHT). However, contrary to that reported in literature, it was found that the friction welding was not a completely solid state joining process as a significant grain boundary liquation was observed in the thermo-mechanically affected zone (TMAZ) of the welded material. The intergranular liquation was due to constitutional liquation of second phase particles like MC type carbides, Ti rich carbonitride particles and d phase precipitates. Liquation resulted in formation of Laves phase particles during welding and a non-uniform distribution of the main strengthening phase of the alloy, g¢ precipitates, during PWHT. Despite considerable liquation, there was no intergranular microfissuring which might be related to the nature of imposed stress during the LFW process. (AU) © 2010 by The Materials, Metals, & Materials Society. All rights reserved.