Low temperature creep in a high strength roller bearing steel

• The microstructure controlled the transient low temperature creep behaviour.
• The bainite structure exposed logarithmic whereas martensite showed power law creep.
• The creep strains were pressure sensitive, higher in tension than compression.
• Non-associate creep models were derived for the creep including the SDE.
• The models recreated tensile and compressive results within engineering accuracy.

Noticeable low temperature creep was established for a bainitic and a martensitic microstructure of the 100CrMnMo8 high strength roller bearing steel. The response revealed primary creep that differed between the microstructures, following a power law for martensite and the logarithmic description for bainite. The detected creep was pressure sensitive, higher in tension than in compression for the same stress level, following the strength differential effect (SDE) at material yielding. Two models were proposed where the stress variable for the pressure effect was based on the Drucker–Prager yield function and deviatoric creep strains were derived from a non-associated von Mises potential. Model parameters were determined from experimental series on the respective microstructure. When the models were evaluated against the experiments the accuracy was of the same order as the effects of different heat treatment batches and different load application rates. The importance of different material parameters in the descriptions was discussed.