Effect of PWHT on Microstructure, Mechanical and Corrosion Behaviour of Gas Tungsten Arc Welds of IN718 Superalloys

摘要

An attempt has been made to perform Gas tungsten arc welding (GTAW) on IN718 superalloy plates with 3mm thickness. Though base metal is having better combination of properties, the welding operations on IN718 alloy resulted in significant drop in its corrosion resistance and mechanical behaviour. The present work aims to improve corrosion resistance and mechanical behaviour of the welds with suitable post weld heat treatment (PWHT).The structural-property relationship of the weldments are judged by correlating the microstructural changes with observed mechanical behaviour and pitting corrosion resistance of the welds in as-received, direct aging (DA), 980STA, 1080STA conditions. Microstructural studied by scanning electron microscopy (SEM) and optical microscopy (OM). Potential-dynamic polarization test conducted to study the pitting corrosion resistance in 3.5%NaCl solution. The present work results established that the better combination of mechanical properties and pitting corrosion resistance were obtained at 980STA than as-received, direct aging (DA),1080STA conditions of GTA welds of IN718 alloy.