Creep behaviour of HP Grade steel at 900°C

Abstract

For the study of the strength of a heat-resistant steel Gr HP microalloyed with Nb and Ti, tensile creep tests were carried out at temperatures in the range of 700 to 950ºC and stresses between 50 and 110 MPa, with an equipment that allows up to three test pieces to be tested independently at constant stress and temperature, controlled by a data acquisition system.

It was observed that at 80 MPa and 900ºC the secondary stage is short and the fracture of the specimen is sudden, however, the deformation rate at that stage was similar to the values determined at lower stresses under the same temperature condition, in disagreement with the predicted response.

The tests were repeated at 900ºC and at stresses of 75, 80 and 85 MPa, and the same behavior was observed. The results of the microstructure analysis, which showed differences in the morphology, density of the carbides at the grain boundary and intragranular, together with the determined hardness values at 80 MPa, validate the loss of strength and the observed behavior.