Effect of cold working on mechanical properties of a cobalt base superalloy

The influence of cold working deformation on the hardness, tensile strength, elongation and microstructure of a cobalt base superalloy used for pistons rings was studied in this paper. The results show that cobalt base superalloy in solid solution condition has a typical metallic tensile curve, while cobalt base superalloy after cold working treatment has no obvious yield step in tensile stress-strain curves. With the increase of cold deformation rates, the tensile strength and hardness of cobalt base superalloy increase gradually, while the plasticity of cobalt base superalloy decreases significantly. A lot of stacking faults and twins appear in the microstructure of the cold working alloy, so the hardening mechanism of the alloy is twinning strengthening.