Creep behaviour characterisation of a ferritic steel alloy based on the modified theta-projection data at an elevated temperature

This paper establishes and examines the constitutive model of the modified theta-projection concept for predicting the creep-rupture behaviour of a 2.25 Cr-1Mo ferritic steel alloy foil at the loading conditions of practical interest. For this purpose, a series of creep-rupture tests are conducted on 0.15 mm thick foil specimens at an elevated temperature of 1 027 K and applied stresses in the range of 90–210 MPa. The creep-rupture behaviour of the foil is well represented using the model of the modified three-parameter theta-projection concept. Each model parameter is well represented as a function of the applied stress. Moreover, the creep failure mechanism was analysed by means of field emission scanning electron microscopy. The results showed that chromium atoms diffuse to the grain boundary and form carbide precipitates at the elevated temperature, leading to inter-granular fracture in the material.