| In this paper,Q345 steel and 304 stainless steel were diffusion bonded.Microstructure and mechanical properties of joint were studied and the conclusions are summarized as follows:(1)Sound joint was obtained by diffusion bonding in the following parameters:the vacuum was 0.6 Pa,the pressure was about 20～25 MPa,the temperature was about 950～1000℃ and the bonding time last for 30～40 minutes.(2)Micro structure and component analysis were studied by OM,SEM,EDS,XRD,and results showed that grain refinement was occurred near interface at the sides of the 304 stainless steel.Single ferrite region generated by carbon loss from pearlite was observed near the interface of Q345,the width of which was 50μm.The element of chromium diffused from 304 stainless steel to Q345 near the interface,which resulted in the formation of alloy ferrite and improved strength in the single ferrite region.(3)Results of the tensile tests showed that the fracture was occurred on the side of Q345 base metal,which was away from the bonded joint.The tensile strength of the specimens was 518MPa and the elongation was about 26.4%.Results of the impact toughness showed that the impact energy was 77.38 J,which was basically identical with Q345 base metal.Results of the bending tests showed that no cracks existed on the surface of the joint.(4)Results of the high frequency fatigue tests showed fracture also occurred on the Q345 base metal which was far away from the interface.At2×106 cycles,fatigue strength of the fatigue specimens on the survival rate of 50%and 95%were 215.36 MPa and 198.50 MPa,respectively. |
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