The Influence of Base Metal Microstructure on Weld Cracking in Manually GTA Repair Welded Cast ATI 718Plus

摘要

The effect of base metal conditions on the weld cracking response of cast ATI 718Plus was investigated in this study, comparing as cast microstructure with pseudo hot isostatic pressing (HIP) heat treatments at 1120, 1160 and 1190°C for dwell times of 4 and 24 h. Linear grooves have been filled using multipass manual gas tungsten arc welding (GTAW) to simulate repair welding conditions. Metallographic investigation revealed cracks in both base metal heat affected zone and fusion zone layers. The heat treatment temperatures chosen below, at and above incipient laves melting temperature of ATI 718Plus were found to have an effect on weld cracking behaviour, with an increased average total crack length in the base metal heat affected zone for both 1160 and 1190°C as compared to the as cast condition and the 1120°C homogenization treatment. The increase in cracking susceptibility shows a correlation with the amount of Nb-rich secondary phases, with lower amounts leading to crack concentration to solidification grain boundaries present from the casting process, increasing the average crack length.