Influence Of Electro-pulsing Tempering Treatment On The Microstru-cture And Properties Of 42CrMo Gear Steel

Gear is an important transmissioncomponent.In order to improve the life and stab ility of the gear,the preparation and performance of the gear steel is particularly impo-rtant.42 CrMo is a Cr-Mo system gear steel,it has good strength,toughness and harden ability,not obvious temper brittleness,it can be used for the preparation of larger crosssection gear.Further improving the mechanical properties of 42 CrMo,can be of great s-ignificance for industrial production.Electrical-pulse treatment is an extre-me non-eq uilibrium process,which produces heat-stress-under electric coupling field effect, the performance of metal materials can be significantly improved. Simultaneously, with e-nergy saving, high efficiency, low cost and any other advantages which make electri-c-pulse treatment more applied.In this paper, we choose 42 CrMo gear steel to study its microstructure evolution and mechanic properties under electric-pulse quenching/tempering treatment, tradition-al quenching/tempering treatment and other mixed tempering treatment. Based on these experiment data, we analyze the strengthening mechanism of electric-pulse treat-ment.Contrasted with traditional quenching treatment, the grain of 42 CrMo is much more fine and its mechanic properties is more excellent after electric-pulse quenching treatment: the size of grain is about 6-13μm, the tensile strength is 1998 MPa with a 81.6% increase, the hardness is 943.2HV with a 186.9% increase, the dislocation density is 1.69×1016m-2, 6.17 times higher than the specimen after traditional quenching treatment.The electric-pulse quenching samples after tempering appears layere tempered m-icrostructure, its mechanical properties are better than the ones of traditional temperi-ng treatment. Samples under electric pulsing has the best mechanical properties of th-e tensile strength of 1810 Mpa, elongation of 16.6%, its product of strength and plasti-city is 30046 Mpa.% with a 79.7% increase contrasted with specimen at initial state. After electric-pulse tempering treatment, the mechanical properties of traditional quen-ching specimen are the worst compared with the other three tempering treatment. Aft-er twice electric-pulse tempering treatment, the traditional quenching specimen will a-ppear intergranular fracture. After all kinds of tempering treatment, the dislocation de-nsity decreased, after electric-pulse tempering treatment, the dislocation density decreased to a lesser exent.After systematical research and analysis, we found that electric-pulse treatment the mechanical properties of metal materials more significantly, which can be a new m-eans of toughening materials instead of the traditional metal heat treatment.