This research has an aim to search for the optimal heat treatment condition after
TIG welding to refurbish fractured turbine blade (cast nickel-based superalloy grade Inconel
738) of land-based gas turbine engines with the most proper final microstructural characteristics.
The Inconel 738 (IN-738) specimens were welded by TIG welding process together then
various heat treatment conditions were applied in order to reach the proper microstructure
with uniform distribution of proper size of intermetallic phase, namely, gamma prime (γ ) in
the metal matrix, for high performance in mechanical properties at elevated temperatures. The
heat treatments consist of solutioning, primary aging and secondary aging at different heating
temperatures. From the results, it was found that the postweld heat treatment provided both
beneficial and detrimental effects depending on initial reheat treatment condition. The lowest
solutioning temperature (1398 K) after weld process provided the most coarsening size of γ
particles in uniform dispersion in base metal zone as well as uniform dispersion of very fine
γ particles in heat affected zone (HAZ) with very high area fraction. Furthermore, the higher
solutioning temperatures after weld process resulted in smaller size of γ particles precipitating
in both HAZ and base metal zone. The highest solutioning temperature of 1478 K resulted in
hot cracking in base metal zone near weld band.