Microstructure And Mechanical Properties Of ZrB2-SiC Ceramic And Nickel Base Alloy Brazed Joint

ZrB2-SiC ceramics have the characteristics of high melting point,high thermal conductivity,high strength,high hardness and excellent corrosion resistance,and are widely used in manned aircraft and supersonic aircraft.However,the development and application of ceramic materials have been greatly restricted by their inherent brittleness and difficulty in machining.Inconel 600 nickel-based superalloy whose main added elements are chromium,iron and nickel is a solid solution reinforced alloy with high melting point,excellent corrosion resistance and oxidation resistance.In the field of aerospace,the structural components such as turbine disc and blade with excellent structural performance can be prepared with it.In this paper,the vacuum brazing joints of ZrB2-SiC ceramic/Inconel 600 nickel-based superalloys were realized at different brazing temperatures,different Cu foam thickness and different holding times by using AgCu,AgCu/Cu foam/AgCu and Ti/AgCu/Cu foam/AgCu composite filler metals,then the influence of brazing parameters on microstructure and mechanical properties of joints was researched.The typical precipitated phases of the joint interface of AgCu brazing ZrB2-SiC ceramics/Inconel 600 nickel-based are Ni-Fe-Cr,Cuss,Agss,(Cr,Fe)7C3.The type of interface products of brazing joints did not change when using different brazing parameters,but the volume fraction,size and thickness of the precipitated phase have changed to a certain extent.With the increase of brazing temperature and the extension of the holding time,the(Cr,Fe)7C3 precipitate near the ceramic side continues to increase and thicken,and the reaction layer of(Cr,Fe)7C3 is gradually formed on the connection surface of ceramics and solder.When the brazing temperature is 900? and the holding time is 5 min,the brazing joints achieved the maximum shear strength 70.7MPa.The fracture mainly occurs on the ceramic side,and the fracture surface is flat,which is a typical brittle fracture.The typical precipitated phases of the joint interface of AgCu/Cu foam/AgCu brazing ZrB2-SiC ceramics/Inconel 600 nickel-based are Ni-Fe-Cr,Cuss,Agss and(Cr,Fe)7C3.After adding the Cu foam to the solder,while the 3D structure of the Cu foam is kept in the joint,and the type of interface products of brazing joints did not change when using different brazing parameters.When the insulation time is too short or the Cu foam thickness is too large,the interface reaction is insufficient,the bonding between the parent materials is not close enough,the insulation time is too long or the Cu foam thickness is too small,the side of ZrB2-SiC ceramics(Cr,Fe)7C3 precipitation is too much,and forms a rod-like structure,which makes the brazing joint brittleness increased,thus reducing the joint shear strength.When the brazing temperature is 900?,the holding time is 15 min and the thickness of Cu foam is 1.0 mm,the brazing joints achieved the maximum shear strength 103.2MPa.The change of technological parameters has little influence on the fracture position of the brazed joint.The fracture position of the joint mainly occurs on ZrB2-SiC ceramics regardless of the change of insulation time or the thickness of Cu foam,and the fracture process is a typical brittle fracture.When brazing ZS and In 600 with AgCu filler metal,the maximum residual stresses in brazed joint is 287MPa.When AgCu/Cu foam/AgCu brazing ZS and In 600,the maximum residual stresses in brazed joint is 141MPa,which is 146MPa lower than that of AgCu solder.Therefore,the brazing of ZS and In 600 with AgCu/Cu foam/AgCu composite filler metal could effectively relieve the residual stress of the joint.The typical precipitated phases of the joint interface of Ti/AgCu/Cu foam/AgCu brazing ZrB2-SiC ceramics/Inconel 600 nickel-based are Ni-Fe-Cr,TiCu,TiFe2,Agss,Cuss,Ti5Si3+TiC.The precipitated phase at the interface of the joint did not change with different holding time.With the extension of the holding time,the precipitation of Ti5Si3,TiC and TiFe2 in the weld continued to increase,the structure of the Cu foam skeleton gradually became sparse.When the brazing temperature is 900? and the holding time is 15min,the brazing joints achieved the maximum shear strength 198 MPa.Compared with the joint fracture under different holding time,the fracture location is mainly occur on ZrB2-SiC ceramics,and the fracture process is a typical brittle fracture.