Ductile-brittle transition in a 9% Cr heat-resistant steel

The mechanical behavior of a P92-type steel was studied by tension and Charpy impact tests in the temperature range of 77-293 K. The yield stress (YS) and uniform elongation increase concurrently with decreasing temperature because the steel exhibits work-hardening behavior. Transgranular dimpled fracturing remains the primary fracture mechanism under tension down to 193 K. Brittle fracture takes place at lower temperatures. At 77 K, the steel exhibits a well-defined yield plateau. Impact tests demonstrate that the ductile-brittle transition (DBT) occurs at 210 K. At 193 K, the energy absorption of 110 J/cm2 at high impacts is attributed to extended areas of crack initiation and a stable crack propagation; the fast fracture load also has a high value. The steel becomes completely brittle at 77 K, at which temperature the absorbed energy falls to 6 J/cm2.