Mechanical Property and Microstructure of Linear Friction Welded WASPALOY

The mechanical properties and microstructural evolution of WASPALOY joined by linear friction welding (LFW) were investigated in this study. In-situ temperature measurements using thermocouple probes indicated exposure of the weld area to a temperature of at least 1400 K (1126 A degrees C). Based on electron backscatter diffraction (EBSD) mapping of the weldments, up to 50 pct reduction in gamma grain size occurred within 0.9 mm of the weld interface as a result of dynamic recrystallization (DRX). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed that progressive dissolution of gamma' precipitates took place from the base metal to the weld interface, where almost no gamma' precipitates were observed. Within 3.3 mm of the weld interface, the gamma' dissolution significantly influenced the hardness profile measured across the extended thermomechanically affected zones (TMAZs). Investigation of strain distributions during tensile testing using the optical Aramis system revealed weak bonding at the edge of the weld due to oxidation. To extrude out oxide layers into the flash, increasing the axial shortening to higher than 1.2 mm is recommended.