Ratcheting Behaviour of a Sensitized Non-Conventional Austenitic Stainless Steel

Austenitic stainless steels are candidate materials for many engineering applications owing to their excellent strength, ductility, toughness even at low temperatures and non-magnetic nature. In heat-transfer pipelines of heavy water reactors of nuclear power plants, underground pipelines etc. the steel is potentially used, where components frequently encounter cyclic loading. However, during prolonged service at high temperature and with aggressive environments the steel suffers from grain boundary corrosion known as sensitization. Further, sensitization in conjugation with asymmetric cyclic loading makes the situation more complex. In such cases usually, premature failure takes place. This investigation is intended to study the effect of sensitization on the asymmetric cyclic loading or ratcheting behaviour of a non-conventional austenitic stainless steel (X12CrMnNiN17-7-5). Relationships between sensitization treatments for different durations with microstructural and tensile property variation were established. Further, ratcheting experiments were carried out at different combinations of mean stress and stress amplitudes. The results indicated that accumulation of ratcheting strain increased with stress amplitude. However, it was inversely proportional to the degree of sensitization (DoS). The increase in brittleness of the material with sensitization led to decreased accumulation of ratcheting strain. The analyses of the obtained results may help the design and safety aspects of structural components made up of similar steels.