Creep evaluation of traditional and nuclear power plant high-temperature components, using small pin-loaded one-bar and two-bar specimens

The high-temperature components in thermal power plants are subject to creep deformation as a result of operating at elevated temperature and high steam pressure. Creep is nonlinear deformation leading to rupture and component failure; therefore, it has to be monitored closely, especially when the high-temperature components approach the last stage of their designed lifetime. This paper presents the design and application of two small specimen types that can be used to assess the severity of creep damage in these components as they age. These specimens can be used to assess the creep strength and remaining lifetime of in-service components. Small material samples can be removed safely from operating component surfaces and then be used to manufacture these small specimens. These specimens can be manufactured and tested easily using pin connection. This paper places emphasis on specimen design and loading for creep testing. Two high-temperature materials (P91 and P92 steels) are used to validate the accuracy of the new testing technique. The creep results obtained from these small creep test specimens are compared with results obtained from corresponding uniaxial creep tests. Very good correlation is found between the two sets of results.