Determination of Fracture Energy Characteristics and Their Anisotropy for 15Kh2NMFA Steel in Impact Bending Tests

Results of complex experimental investigations on the determination of energy characteristics of fracture propagation in Charpy specimens cut in three different directions during impact bending tests for heat-resistant 15Kh2NMFA steel are presented. Tests were conducted over a wide temperature range on an instrumented vertical coping equipped with a high-rate data logging system. According to the test results, load diagrams were obtained. Total strain and fracture energy and its components were determined: crack nucleation energy, ductile crack growth energy, brittle crack propagation energy, and ductile final rupture energy. The use of quantitative fractography methods made it possible to determine both the specific strain and fracture energies, their components, and the average propagation rates of brittle and ductile cracks in the specimens' material. Critical brittle fracture temperatures were determined by two methods. The cutting direction of specimens significantly influenced the fracture energy characteristics and crack propagation rates in the material, which might affect the accuracy of strength and resource estimation of the NPP first contour components.