Development of thermo-mechanical treatments of a maraging steel for yield strengths above 3 GPa

Hot-rolling of austenite and cold-rolling of martensite were combined with aging treatments to obtain new microstructures in a maraging steel with a high Mo-content. Purpose of the investigation is to acquire an optimum combination of ultra high yield stress (σr>3000 MPa) and ductility (or toughness). The best results were obtained by treatments consisting of high amounts of plastic deformation between 1000°C and 600°C (ausforming) and aging of the martensite which had formed from the deformed austenite. Ausaging around 550°C induced pronounced intercrystalline embrittlement. Intercritical heat treatment at 700°C provide considerable ductility (uniform elongation) however, insufficient strength (<2000 MPa). The most favourable thermo-mechanical treatments are discussed in context with fabrication methods for the investigated steel.