Development Of Carbon Base Materials Brazing Technology For Plasma Facing Components In EAST

Carbon base materials such as graphite are widely used as plasma facing material(PFM)in fusion experimental devices due to their high melting point,strong thermal shock resistance and good compatibility with plasma.In the manufacturing of plasma facing components(PFCs),the connection technology between PFM and heat sink is the key manufacturing technology.At present,in the EAST device,the graphite as the PFM is bolted to the copper alloy(Cu-Cr-Zr)heat sink by screw.Due to high contact thermal resistance,the thermal load resistance of plasma facing components(PFCs)is low.Therefore,it is of great significance to study the metallurgical connection technology of Carbon base materials and copper alloy.In order to alleviate the thermal stress in actual working conditions,the oxygen-free copper with good ductility is generally used as the intermediate layer for the connection between PFM and heat sink material.In this paper,the dierct brazing technology between Carbon base materials and oxygen-free copper is studied.Different kinds of silver-based titanium filler metals are adopted to join GA graphite,atek graphite and CFC Carbon base materials to oxygen-free copper,the parameters of solder,brazing temperature,clamping pressure and cooling speed are optimized.A good joint between carbon composite and oxygen-free copper is achieved,the joint is smooth,and the base material has no cracks and other defects.The average joint strength of atek graphite and oxygen-free copper reached 12MPa;When the oxygen-free copper is used as the intermediate layer,the joint strength is higher,and the highest strength reaches 39MPa,exceeding the strength of the graphite base material itself.On the basis of carbon composite material and oxygen-free copper brazing process,the development of plasma facing components using carbon material as PFM was carried out.The brazing connection of Carbon base materials and oxygen-free copper and copper alloy(Cu-Cr-Zr)can be realized by both one-step welding and two-step welding.The non-destructive testing technology of joint interface is studied and joint interface of atek graphite and oxygen-free copper can be detected by water immersion ultrasonic technology,Interface brazing rate exceeds 90%.GA graphite and CFC cannot be detected by ultrasonic wave due to their large porosity,and it is also difficult to detect multi-layer brazing structure by ultrasonic wave.Infrared nondestructive testing technology is limited to the thickness of carbon material and structure type of test sample,and the testing result is not ideal.The thermal load resistance test was carried out on the small samples,and the results showed that at the water flow rate of 5m/s,the heat load can withstand maximum 11MW/m2,and there is no surface damage under the condition of 1000 times of 5MW/m2 heat load.The carbon material brazing technology was applied to the first wall area of EAST device where the NBI penetrates the plasma and irradiated to.The structure is optimized and the finite element analysis is carried out according to the actual working load,the results show that the temperature and stress of each component of the new first wall meet the design requirements.New structure was manufactured and inspected,replacing the old first wall and was successfully installed in the EAST device.After a round of plasma discharge experiment,it was verified that there was no obvious damage on the surface of the CFC.