Modeling interaction between creep deformation and oxidation of P91B steel

摘要: [en] P91B steel is a candidate material for welded high temperature components of nuclear power plants because of its superior resistance to type IV cracking in comparison to that of P91 steel. Therefore generation of reliable creep strain time data on this steel is of considerable interest. The paper presents constant load creep test data over a range of stresses (190-50MPa) and temperatures. Particular emphasis has been given on the effect of creep exposure on the loss of its rupture ductility. While most of the tests ran until rupture a few tests were interrupted after a measurable amount of elongation due to creep was recorded. The diameters of these were found to have increased. This unexpected increase in diameter has been attributed to oxide scale growth. Although most creep tests on such steels are done in air, little attention is paid on the formation of oxide scale on the specimen. Accelerated oxidation tests were also performed on this steel using thermo-gravimetric balance. The weight gain data were used to estimate rate constants for oxide scale growth. A model that connects oxidation with creep strain has been developed. This has been used to predict the conditions under which such an unusual phenomenon can be encountered if tests were interrupted.(author)