Study On Preparation And Performance Of Plasma Facing Tungsten-based Composites

Tungsten-based composites are the most promising plasma facing materials for future fusion reactors,but tungsten material is not perfect,which also have some shortcomings,such as brittleness at room temperature,recrystallization brittleness,and low resistance to irradiation,which greatly restrict their application in fusion reactor.The tungsten-based composites used as plasma facing materials are prone to recrystallization due to the long time in high temperature and high heat environment,which increases the brittleness of the materials and greatly reduces the thermodynamic properties.Therefore,it is urgent to improve the performance of tungsten-based materials to meet the operation requirements of fusion reactors.Graphene（Gr）is a new type of carbon material with stable nanocrystalline structure,which has excellent properties such as high toughness,electric and thermal conductivity,carrier mobility and high strength,and which is one of the ideal doping phases for metal matrix composites.MAX phase(chemical formula is M_（n+1）AX_n.Where,M is the transition metal element;A main group element;X is carbon or nitrogen)has high temperature and corrosion resistance and excellent toughness of both metal and ceramic,which is one of the best reinforcement phase choices in tungsten-based composite.In this paper,pure tungsten,graphene-reinforced tungsten-based composites（W-Gr）and MAX reinforced tungsten-based composites（W-Ta₂Al C and W-V₄Al C₃）were prepared by spark plasma sintering method with Gr and MAX as reinforcement phases at 1800℃and 50MPa.The density,microhardness,bending strength,tensile strength and fracture morphology were characterized and analyzed to study the influence of doping amount of reinforcement phase on the properties of tungsten-based composites.The main research contents and results are as follows:（1）It is found that the grain size of pure tungsten is about 5.5μm,and the grain size of W-Gr composite doped with 0.1 wt%is about 4.8μm,which is obviously finer than that of pure tungsten.The microhardness of pure tungsten is 363.6 Hv,and the microhardness of W-Gr composite doped with 0.2 wt%is 878.8 Hv,which is about 141.7%higher than that of pure tungsten.The bending strength of pure tungsten is 35.5 MPa,and the bending strength of W-Gr composite doped with 0.2 wt%is 339 MPa,which is 854.9%higher than that of pure tungsten.The tensile strength of pure tungsten is 344 MPa,and the tensile strength of W-Gr composite with doping content of 0.3 wt%is 374 MPa,which is about 8.7%higher than that of pure tungsten.（2）The density of W-Ta₂Al C composite doped with 1.5 wt%is 90.71%,which is about8.13%higher than that of pure tungsten;The grain size of W-Ta₂Al C composite doped with4.5wt%is about 1.6μm,which is significantly refined compared with pure tungsten.The microhardness of W-Ta₂Al C composite doped with 4.5 wt%is 503.2 Hv,which is 38.4%higher than that of pure tungsten.The bending strength of W-Ta₂Al C composite doped with4.5 wt%is 382.5 MPa,which is 46.27%higher than that of pure tungsten.The tensile strength of W-Ta₂Al C composite doped with 4.5wt%is 436 MPa,which is about 26.74%higher than that of pure tungsten.（3）The density of W-V₄Al C₃composite doped with 1.5 wt%is 87.55%,which is4.97%higher than that of pure tungsten.The grain size of W-V₄Al C₃composite doped with0.5 wt%and 1.5 wt%is about 1.5μm,which is significantly refined compared with pure tungsten.The microhardness of W-V₄Al C₃composite doped with 4.5 wt%is 518.7 Hv,which is 42.7%higher than that of pure tungsten.The bending strength of W-V₄Al C₃composite doped with 4.5 wt%is 420 MPa,which is about 60.61%higher than that of pure tungsten.The tensile strength of W-V₄Al C₃composite doped with 4.5 wt%is 378 MPa,which is about 9.88%higher than that of pure tungsten.（4）Helium plasma irradiation experiments were carried out on the pure tungsten,commercial tungsten and W-V₄Al C₃with the best comprehensive properties.The number and density of the nanofilamentous structures,the relative area of the nanofilamentous structures in the surface of the sample,and the damage degree of the surface of the sample increased with the increase of the irradiation dose and duration.Research shows that:Nanometer filamentous structure of W-V₄Al C₃growth more evenly,there is a small number of clusters,and the growth of nanometer filamentous structure on the surface of the pure tungsten is relatively uniform,there are a large number of clusters,confirmed the tungsten doping amount of MAX is helpful to reduce the sample number of vacancy defects in irradiation for tungsten materials to improve the performance of anti irradiation has certain positive role.