Modeling of Fracture Toughness of Degraded HR3C Steel in Relation to Microstructural Changes

The article documents the cause of a sharp decrease in the fracture toughness of HR3C austenitic steel intended for heat exchange surfaces of supercritical energy blocks during its exposure to elevated temperature. The documentation of the cause of the decrease in fracture toughness is based on a combination of fractographic observation of the fracture surfaces of the tested samples, linked through ongoing precipitation changes in the steel to the fracture toughness of the steel. The result is a description of the decrease in fracture toughness in relation to the Larson-Miller parameter and subsequently the change in fracture toughness in relation to the precipitation changes in HR3C steel. This dependence provides a tool for numerical calculations and simulations of heat exchange surfaces of power plants made of HR3C steel and the simulation of their behavior when cracks are present.