Cracking Susceptibility Study of Inconel 600 Alloy Using Varestraint and Hot Ductility Test

摘要

The weldability and crack susceptibility of Inconel 600 were studied using varestraint test and hot ductility test along with a GTA-welding experiment. The effect of heat input on the microstructural change was investigated. Higher current resulted in grain coarsening in the weld metal and in the HAZ. Higher heat input resulted in migration of some precipitated particles on the grain boundaries. The results of hot ductility test revealed that higher heat input (12kJ/cm) caused delay in ductility recovery of HAZ upon cooling which implied a larger crack susceptible region and brittle temperature range. A new criterion in determining the hot ductility test temperature of Inconel 600 was proposed. We found that hot cracks in the fusion zone of the varestraint specimen often propagated into HAZ under higher heat input. In stead of heat input, welding current showed a more pronounced influence on the total crack length (TCL) in the varestraint test. Higher crack susceptibility was observed at higher welding current although heat may remain the same. Therefore, the welding current is a better index for Inconel 600 in the varestraint test. The formation of liquation cracking near the fusion zone was interpreted by comparing the EDS result with a tertiary phase diagram of Ni-Cr-Fe alloy.