Effect of holding time on microstructure and mechanical properties of 1Cr18Ni9Ti stainless steel joint brazed by amorphous BNi-2 filler metal
This investigation explored how the interfacial microstructure and mechanical characteristic of 1Cr18Ni9Ti stainless steel/amorphous BNi-2 filler/1Cr18Ni9Ti brazed joints were affected by heat preser-vation time,providing theoretical support for manufacturing reliable brazed joints.Amorphous BNi-2 filler metal was used to braze 1Cr18Ni9Ti stainless steel at 1 000℃for various holding time.The interaction mechanism between the filler metal and the base metal were characterized by SEM and EDS.Further-more,testing was conducted to evaluate the shear strength of the joints and to analyze their fracture mech-anism.The investigation focused on the evolution of interfacial structures and the mechanical properties of brazed joints under varying holding time.The main components of the brazing seam are mainly Ni(s,s)and CrB.With the increase of heat preservation time,the width of the brazing seams decreases and the intergranular infiltration of CrB increases.The shear strength of the joints exhibits an initial increase fol-lowed by a decrease as the holding time increases.At a holding time of 10 minutes,the shear strength of the brazed joints peaks at 248 MPa.When the holding period is short,large blocky CrB particles are dis-tributed in the center of the brazed seam,which is the source of cracks exhibiting brittle fracture.As the holding time becomes longer,the large CrB blocks become smaller and the fracture location becomes a diffusion zone,exhibiting ductile fracture and increased strength.When the holding period is further pro-longed,massive CrB permeates into the steel along the grain boundary,causing it to become a weak zone and fracture in the intergranular infiltration zone,resulting in brittle fracture.Amorphous BNi-2 filler is suitable to braze 1Cr18Ni9Ti stainless steel.By changing the holding time,the transition behavior of ele-ment B in the filler can be controlled,thereby regulating the weld microstructure and obtaining the best performance joint.
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