Preparation and Mechanical Properties of 42CrMo/40CrNiMo Dissimilar Steel Joints Prepared by Diffusion Bonding

摘要

In this paper, using CuZn alloy as interlayer, 42CrMo/40CrNiMo dissimilar steel joints were prepared by vacuum diffusion bonding, and the effects of holding time on microstructure and properties of 42CrMo/40CrNiMo joints were studied. The microstructure and mechanical properties of 42CrMo/40CrNiMo joints were analyzed and characterized by optical microscope (OM), scanning electron microscope (SEM), energy disperse spectroscopy (EDS), universal mechanical testing machine and vickers hardness tester. The results showed that when the bonding temperature was 780°C, the bonding pressure was 0.02 MPa and the holding time were 5-30 min, obvious interface transition zones formed through diffusion reaction of CuZn interlayer to 42CrMo and 40CrNiMo base materials. The bonding region was dense and continuous with a good combination. In the joints prepared at different conditions, the microhardness of interlayer was lower than base materials. With the increase of holding time, the shear strength of 42CrMo/40CrNiMo joints increased at first and then decreased. The maximum joint shear strength, with the value of 135.86 MPa, was obtained when the holding time was 15 min. Meanwhile, the load-displacement curves and fracture surfaces indicated that the fractural mode of 42CrMo/40CrNiMo joints was ductile-brittle mixed fracture, in which brittle fracture was dominating.