Microstructure And Mechanical Properties Of Silicon Carbide Joints Brazed With YAS Based Oxide Glass In Air

Due to the high temperature and high strength,low thermal expansion coefficient,high chemical stability,and radiation resistance,SiC ceramic material is considered to be a nuclear reactor with the ideal candidate for the high temperature parts material,in the current study.In nuclear reactors,however,the application of high temperature components,the use of ceramic parts are very large and is responsible for the size,directly produced conform to the required size and shape of the ceramic implementation difficulty is too high,so to get to the big size of the ceramic complex components,need through the connection of a material to achieve.Oxide glass has the advantages of adjustable coefficient of thermal expansion and stable performance at high temperature,which can meet the requirements of high temperature resistance,radiation resistance,corrosion resistance and low activation of joints which can not be satisfied by active metal brazing.In this paper,two kinds of system oxide glass are used as solder in the air to brazing the SiC ceramic.Studied the system of oxide glass composition and process parameters in the process of brazing on brazing joint between the influence of the microstructure and mechanical properties;under the optimal ingredient and the optimal process parameters,studied the adding of different nucleation agent on the properties of solder and coupling effects.The results show that:?1?The oxide glass of YAS-25 and YAS-30 can be used to realize the reliable connection of ceramics in the air.Under 1450 ^oC,the YAS-25 oxide glass joint organization with the increase of the holding time gradually uniformity and densification,glass phase gradually reduce,crystalline phase increases gradually;When the thermal insulation time is increased,the holes,cracks and unconnected defects in the joints of the joints begin to increase significantly.Before the time of heat preservation of 60 min,the shear strength of joint increased with the increase of the holding time,the joint shear strength increases with the drop of heat preservation time,the peak shear strength of joint 135.7 MPa appeared at 60 min.YAS-30 oxide glass system showed the same change trend,the peak shear strength 107.69 MPa appeared at 60 min.?2?Nucleation agent is added in the YAS-25 oxide glass for brazing ceramics connection in the air,the trends of the joint microstructure and mechanical properties are same with YAS-25.Under 1450 ^oC,The adding amount of Ta₂O₅ is 1 wt.%,the?3?heat preservation time is 60 min,shear strength can reach 145.82 MPa.The adding amount of ZrO₂ is 3 wt.%,the heat preservation time is 60 min,shear strength is 43.69 MPa,Ta₂O₅ promoted the crystallization of vitreous body,improve the mechanical properties of joint,ZrO₂ damage the structure of silica network,reduce the mechanical properties of joint.