Performance of repair welds on aged 2.25Cr-1Mo boiler header welds

In order to clarify the performance of repair welds on power boiler, thick parts such as header and steam piping, an ex-service aged 2.25Cr-1Mo header was repaired using SMAW with postweld heat treatment and the mechanical properties of the repair welded joints were experimentally evaluated. Creep rupture life of the repair welded joint was almost same as that of service-degraded base metal and heat-affected zones. It was proved that the life reduction would not be caused by repair welding. In creep-fatigue tests with strain holding, some type of repair welded joints was fractured at the heat affected zone caused by repair welding. This may be caused by strain concentration at the heat-affected zone under strain holding. Charpy impact toughness of the simulated heat affected zone due to repair welding was much higher than that of service-degraded base metal. It was proved that the toughness would be restored by repair welding.