Effect of Filler Metals on Creep Properties of 2.25Cr-1Mo Steel Weld Joints Prepared by GTAW Process

Abstract

This research aims at comparing creep properties at elevated temperatures obtained on welding 2.25Cr-1Mo steel using gas tungsten arc welding (GTAW) with ER90S-G and ERNiCrMo-3 filler metals. The high temperature accelerated creep rupture test of 2.25Cr-1Mo welded samples was investigated over 139 to 315 MPa stress range at temperatures of 550 °C, 600 °C, and 650 °C. The samples were preheated at 250 °C for 0.5 hours and post-weld heat-treated at 690 °C for 1 hour. The results showed that the accelerated creep rupture lives of lower applied stress specimens were much longer than those of higher applied stress, when both welded materials were tested under same temperature conditions. The service lifetime of the welded materials can be predicted using the extrapolation of the Larson-Miller parameter. Creep surface fractures were investigated using SEM fractography that indicated the weldment fracture modes consisted of dimple ruptures and micro-voids coalescence in the fibrous matrix of the intercritical region of HAZ. Similar high-temperature creeps service lives were found in both welded materials.