Effect of transient liquid phase bonding followed by homogenization on the microstructure and hot tensile behavior of Inconel 738 superalloy

Inconel 738LC (IN-738LC), a nickel-based superalloy, was joined by the transient liquid phase (TLP) bonding method using a BNi-2 filler metal. The bonding process was carried out at 1120 degrees C under vacuum for 45 and 120 min and was followed by the standard heat treatment (SHT) to homogenize the joints. The microstructures of the specimens were studied by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM). Following the microstructural investigation, the microhardness tests on the homogeneous specimen showed a uniform distribution in the bond region. Next, the base metal (BM) and the homogeneous TLP joint were subjected to hot tensile testing at 650, 750, and 850 degrees C under similar conditions. A comparison of the hot tensile test results revealed two significant facts about the effects of TLP bonding followed by homogenization on the tensile properties, namely, the lack of any increase in the hot tensile behavior over the studied temperature range and the degradation of mechanical properties. The yield strength and the elongation of the homogenized TLP joint were found to be, respectively, 96% and 61% of those of the BM at 850 degrees C.