Research On Process And Microstructure Properties Of Diffusion Bonding And Brazing Of Cu-0.15Zr Alloy To GH3030 Alloy

In rocket motor thrust interior wall,the status of Cu-0.15 Zr alloy’s application is very high,for engine components,GH3030 superalloy is the basic material, For these two kinds of materials,how to get high quality welding joint become a research focus.In this paper, no-interlayer,pure Cu interlayer is used to diffuse bonding Cu-0.15 Zr and GH3030,in addition, brazing experiment is carried out that using BAg50 Cu as filler metal. The interfacial microstructures of the joints obtained by using different interlayers and welding parameters are investigated by SEM,EDS and XRD,and their properties are tested. Furthermore, simply expounds the element diffusion mechanism of Cu/Ni in interface reaction layer.According to the investigation, the typical interfacial microstructure isⅠ, Ⅱ two layers,the layerⅠis(Cu-Ni)ss, speculate Cu-Zr、Zr2Ni7 and punctuate α-Cu,Cu9 Si phases distribute in it.In layer Ⅱ, distributie Cr3Ni2 Si and rich-Cr phases. The increase of welding temperature, holding time and pressure leads to an increased rate of welded, But the interface area will appear Kirkendall crack.The temperature is too low, holding time is too short or too long, tensile samples are fracture in the parent metal, The highest joint deformation is 23%.The microhardness peak of interface area is located in the center of weld,for hardness,welding temperature cause the biggest influence,the influence of welding stress is minimal. The best welding parameters are T=720℃,t=90min and P=25MPa.Using Cu as the interlayer, When the temperature exceed 700℃, the typical interfacial microstructure isⅠ, Ⅱ two layers,no interspace existence,too high temperature will lead to tissue coarsening,in addition, tiny holes appear.With the increase of the welding temperature,the tensile strength rises first and fall later, the temperature is too low or too high,tensile samples are fracture in the weld, the highest joint deformation is 11%.With the extension of diffusion time,the width of reaction layer increased, meanwhile,the number of brittle phases increase and the its size grow up, tensile strength rises first and fall later,all tensile samples are fracture in the parent metal. With the increase of the welding stress,in interface,the number of interspace reduce, the width of reaction layer increased,the tensile strength rises first and fall later,only one sample that bonded under 5MPa fracture in the weld, the joint deformation reach 15% when welding stress is 30 MPa.In fracture surface, the dimples were non-equiaxed,many holes existed and the snake slip line appeared in dimple wall at Cu-0.15 Zr side,the second phases were present on both sides in the bottom of the dimples, the fracture type was intergranular ductile fracture.During the vacuum brazing process, When brazing temperature is too low or holding time is too short, the brazing weld microstructure is Ag-Cu eutectic structure,under the parameters of T=885℃ and t=5min,the layer(Cu-Ni)ss Ⅰ formed in interface.When brazing temperature is too high or holding time is too long,the width of layer Ⅱ increased,many interspaces existed in brazing seam.No matter how the temperature and holding time changes,the tensile strength rises first and fall later,the highest tensile strength 253 MPa.the layer(Cu-Ni)ss Ⅰ formed in interface when molybdenum wire inexistence.When brazing clearance is 0.05 mm,the width of layerⅠreduced,the number of carbide phase in layerⅡincreased.When brazing clearance is 0.1mm,layerⅠdisappear,the size of carbide phases in layerⅡgrow up.When brazing clearance is 0.15 mm,large area of interspaces existed in brazing seam.With the increase of brazing clearance,the tensile strength declined, the highest tensile strength is 266 MPa.Large amounts of dimples appear in fracture surface and the size is nonuniform,the big dimples and small dimples cross distribution,the carbide phases were present in the bottom of the big dimples and the snake slip line appeared in dimple wall,the fracture type was intergranular ductile fracture.No molybdenum wire exist,T=885℃and t=5min are the best welding parameters.