Qualification of P91 welds through Small Punch creep testing

The deployment of the martensitic alloy P91 in future nuclear plant components operating in the creep regime depends very much on the performance of joints, found occasionally susceptible to failure in fossil fuel fired plant A completely novel approach is proposed to assess the integrity of P91 weldments which relies on the determination of the creep properties of the different zones of the weldment on a micro-scale based on the Small Punch (SP) testing methodology. Results are presented from the Small Punch creep tests carried out exactly following a CEN Code of Practice for the various constituent zones of the weldment and the potential weaknesses are identified within the heat affected zone. In addition, the SP test is applied to determine the fracture properties of the weld compared to the parent metal, showing the expected shift related to the test method in the ductile brittle transition temperature and the inferior performance of the weld metal.