Loading rate and temperature effects on the fracture toughness of a high strength bearing steel

Abstract Fracture of martensitic AISI 52100 steel with 12% retained austenite was experimentally studied at temperatures below the tempering temperature by KIc tests and at extremely low loading rates. Depending on temperature, KIc and JC decreased with 6% to 23% for slow rates. It increased with temperature at standard rate but not for slow loading. FE-simulations with elasto-plasticity, phase transformation and low-temperature creep predicted increased crack tip zone with inelastic strains for slow compared to standard rates. The changes in KIc due to temperature and loading rate was explained in terms of creep and strain-induced transformation at the crack tip.