Study on the Fracture Mechanism of the P91 Steel During Small Punch Tensile Testing

Abstract

This paper investigates the fracture generation processing of the P91 steel during a small punch tensile test. P91 disc specimens, 8 mm in diameter and 0.5 mm in thickness, were tested in a small punch test rig at 600 °C using a constant displacement rate of 2 µm/s. Interrupted tests were performed to investigate the crack generation and evolution of P91 in small punch tensile tests. The disc-shaped specimens were deformed into domes of different depths during the tests. Cross-sectional microstructure analysis revealed that thinning and circumferential necking started to occur at the edge of contact before the maximum load was reached, and then significant point necking occurred in the circumferential necking area after the maximum load. The crack formed during the tests aligns with the plastic flow of the specimen. Alignment of crack propagation occurred in the plastic deformation direction, before achieving the maximum small punch load.