Mechanism of T23/12Cr1MoV dissimilar steel welding failure in high temperature reheater

Fracture mechanism of T23/12Cr1MoV dissimilar steel welding in high-temperature reheater operated for 8 000 hours in the 1 900 t/h boiler was researched by means of macro-morphology analysis of crack characteristics,hardness test and metallographic examination.The results show that the martensitic organization become hardened in the weld and the heat affected zone without preheating and heat treatment after weld,and the grain boundaries became weakening because of grain coarsening in coarse grain zone.On the condition of higher temperature, welding residual stresses and high steam pressure of pipes,the stress concentration in the interfacial of welded joint and coarse grain zone was accelerated.With the increasing of applied stress plasticity,the crack between the grain boundary of coarse grain zone and welded point was emerged.The reheated cracks are the main reason for the welding failure of T23/12Cr1MoV dissimilar steel in high-temperature reheater.