Effect of tig welding parameters on strain-age cracking in joining nickel-based superalloy, GTD-111 with Inconel 625

Abstract

Excellent mechanical properties at high temperature of nickel-based superalloys brought them to extensive application in severe operating conditions. However, the great mechanical properties deteriorate after long-term exposure to high temperature and it frequently causes failure of the component e.g. cracking. TIG welding is considered as an economical way to refurbish the minor damage component as replacement with new one is costly due to high material cost and complexity in manufacturing processes. Unfortunately, heat from welding that applies to the component may create new cracks during and after process from liquation and strain-age cracking. This phenomena is problem especially in precipitation-hardened alloy e.g. GTD-111. Several mitigations, such as pre-weld heat treatment, are proposed to avoid weld cracking occurrence, but most of them require additional process which takes time and cost. In this work, four different TIG welding conditions were studied in non-pre-weld heat treated GTD-111 with IN-625 filler wire for their effect on crack occurrence after welding and after post-weld heat treatment (PWHT). Cracking in heat-affected zone (HAZ) was observed in none of as-welded condition specimens. After PWHT, cracking was found in condition in one condition with welding energy of 198 W. The microstructure study showed the possibility to produce crack-free TIG weld of GTD-111 without pre-weld heat treatment process.