Surface hardening by cryogenic deep rolling

Cryogenic deep rolling of metastable austenites is a new approach to achieve martensitic surface hardening of steel components. By combination of thermal and mechanical loads, more stable microstructures can be applied in the alternative heat-treatment-free production line referred to as cold surface hardening. Subsequent to the soft machining, the workpieces are exposed to the mechanical loads of a deep rolling process and a cryogenic treatment applying CO2-snow simultaneously. The hybrid process causes plastic deformation and strain induced martensitic transformation into depths of up to 1.5 mm. The resulting surface integrity includes high compressive stresses, low surface roughness and high hardness due to the phase transformation.