Vacuum Diffusion Welding Of 304L Stainless Steel And Zircaloy-4 Alloy Based On Ag And Ag/Ti Multiple Layers

Zirconium al oys have excel ent properties,their small thermal neutron absorption cross sections are widely used as fuel cladding tubes and other structural components in nuclear power water-cooled reactors.Stainless steel is a traditional al oy material,which is widely used in automotive industry,mechanical manufacturing,electronic industry and biochemica l fields.It has excel ent corrosion resistance,high temperature resistance,creep resistance and welding performance.The application of zirconium al oys in nuclear power field can be brought into full play by studying the bonded of zirconium al oys and Stainless steel.In this paper,vacuum diffusion bonding of 304L stainless steel?SS?and Zircaloy-4 was carried out using pure Ag and Ag/Ti as multiple interlayers.The effects of process parameters?heating temperature,holding time and pressure?on the microstructure and mechanica l properties of welded joints were investigated.The interface composition and bonding mechanism were clarified.The interface area and microstructure,element distribution and fracture of welded joints were analyzed by OM,SEM,EDS and X-ray diffraction.The phase composition and morphology of the joint were observed and analyzed.The mechanica l properties of the joint were tested,including hardness test and shear test.When the holding time is 15 minutes,pure Ag is used as the intermediate layer,the joint of 304L stainless steel and Zr-4 al oy is composed of 304L/Ag/AgZr+Ag/AgZr+?-Zr/Zr-4.When the holding time is 30 minutes or more,Ag and Zr-4 alloy produce two sub-layers.The joint is composed of 304L/Ag/AgZr+Ag/AgZr+AgZr+AgZr₂+?-Zr/Zr-4.With the holding time prolonging,the intermetallic compound mixed layer of the joint becomes thicker gradually,and the maximum shear strength of the joint is only 37.75 MPa.When the holding time is 15 minutes,the fracture surface of the joint is located at 304L/Ag interface,and when the holding time is longer than 15 minutes,the fracture surface of the joint is located at the newly formed AgZr intermetallic compound?IMC?layer between Ag/Zr-4 interface.The vacuum diffusion welding of 304L stainless steel and Zr-4 al oy was carried out Ag/Ti multiple interlayer.By adjusting the process parameters,it was found that the joint consisted of 304L/Ag/Ag+TiAg/Ti/Ti?Zr?/Zr?Ti?/Zr-4,when Ti was not completely consumed.When Ti is completely consumed,the joint consists of 304L/Ag/Ag+TiAg/Ag?Ti,Zr?₂/Ti?Zr,Ag?/Ti?Zr?/Zr?Ti?/Zr-4.The formation of TiAg did not harden the joint obviously,and the relative content of TiAg in Ag+TiAg mixed layer decreased gradually with the increase of temperature.The growth activation energy of Ag/Ti interface reaction layer is 97.914KJ/mol.The location of shear fracture surface of 304L/Ag/Ti/Zr-4 joint was not changed by the change of process parameters.It was between 304L/Ag interface.There were dimple and lamellar cleavage steps in the joint at 800?.The fracture mode was a mixed fracture composed of ductile fracture and brittle fracture.When the heating temperature is 850 and900?,the fracture surface presents a dense block structure with a certain amount of dispersed phase,and the fracture form is brittle fracture along grain boundary.The maximum shear strength is 165.70 MPa.