The high-temperature performance of nickel-based transition joints: I. Deformation behaviour

The microstructures present in nickel-based transition joints are complex so that different regions of the weldment exhibit wide variations in creep strength. Experience suggests that long-term damage develops at the weld interface with the 2.25wt.% Cr–1wt.% Mo steel. High-sensitivity creep experiments, involving detailed local strain measurements, have demonstrated that, for new welds, deformation takes place predominantly in the low alloy steel heat-affected zone. Provided strain is calculated using an appropriate value of gauge length, and it is shown that the stress and temperature dependence of deformation are sensible and that results agree with the Monkman–Grant concept. A relationship is established between strain accumulation and life fraction, indicating that deformation monitoring offers a potential method of assessing damage development.