Research On The Microstructure And Performance Of The Connection Between ODS-W And Dissimilar Materials

The joining of dissimilar materials is to combine two different materials by certain means.Tungsten is the best candidate material for the first wall,while plasma facing materials are required to be effectively connected with heat sink materials to ensure that the heat load on the surface of plasma facing materials can be quickly transferred due to the harsh conditions.Copper is an ideal heat sink material because of its high thermal conductivity and low coefficient of thermal expansion.ODS-W and TZM alloys,both of these are used in high-temperature structures,and effectively connecting the two can expand their high temperature applications.In this paper,ODS-W/Cu power and ODS-W/TZM alloy were successfully joined by pre-modifying the surface of ODS-W and using the Spark Plasma Sintering(SPS)technique.The effects of different temperatures on the microstructure morphology of the joined joints,the influence on the diffusion distance of elements of the joints,and the influence on the properties of the joints were studied.The main results are as follows:(1)The surface modification(anodic oxidation + hydrogen reduction)of ODS-W resulted in the formation of a uniform pore structure with a diameter of 100 nm and a depth of 400 nm on its surface.The specific surface area is increased,which is conducive to the subsequent connection.(2)The microstructure morphology of the joints at different temperatures was investigated,and the results showed that at 850 °C,the ODS-W/Cu bonding was not good and there were obvious cracks at the joints.With the increase of temperature,no cracks were observed at the ODS-W/Cu joints.When the temperature reached 980 °C,Cu had diffused to the W side in some regions.As the temperature increased,the joints of ODS-W/TZM alloy became blurred,and obvious diffusion occurred at the joints,no obvious defects were found at the joints under different temperatures.(3)The diffusion distance of the elements of the joints at different temperatures was studied.The results showed that as the temperature increased,the inter-diffusion distance between W and Cu was increasing.The inter-diffusion between them could be promoted when yttrium oxide particles were present near the interface.At 980 °C,The mutual diffusion distance between W and Cu was 1.3 ?m.At 1500 °C,the mutual diffusion distance of W and Mo was the farthest,reaching 1.75 ?m.When yttrium oxide particles were present at the interface,the diffusion distance of W to Mo increased from0.3 ?m to 0.8 ?m,and the diffusion distance from Mo to W increased from 0.3 ?m to 1?m.(4)The mechanical properties of the joints at different temperatures were investigated.The results show that the hardness at the joints of the ODS-W/Cu joints could reach 200 HV,and the tensile strength of the ODS-W/Cu joints could reach 312 MPa.The hardness of the ODS-W/TZM alloy joints could reach 411 HV,and the tensile strength of the ODS-W/TZM alloy joints could reach 485 MPa.(5)The laser thermal shock test was conducted on the joints.The results showed that the thermal shock resistance of the ODS-W/Cu joints at 980 °C was better than that of the joints at other temperatures.There is no crack at the joint of the ODS-W/TZM alloy joints at 1500 °C.