Preparation And Properties Of W-TiC Composites Based On Plasma Facing Materials

Tungsten and its composites are very promising for use as high heat flux components and high-power density structural materials in radiation environments because of their excellent compatibility with liquid metals, high melting points, low thermal expansion coefficients and low sputtering yield, etc. However, these mate-rials can't totally satisfy the requirements of fusion devices. Therefore, it is neces-sary to develop tungsten composites with much improved properties. The aim of this paper is to fabricate W-TiC composites with high properties. The work includes: W-10wt%TiC composites were prepared by high energy ball milling and vacuum hot-pressing (VHP). The parameters' influences on the properties of W-10wt%TiC composites were investigated of milling and sintering process, the sintering mechanism of milled powders was also investigated. Nanometer TiC particle (Nano-TiCp) dispersion strengthened ultra-fine grained W matrix composites were prepared by ball milling and VHP. The influences of the content and strengthening mechanisms of Nano-TiCp on the properties of nanocomposites were investigated. The high heat load properties of W-10wt%TiC, W-0.5wt%TiC and W-lwt%TiC were measured under high energy electron beam. The results are following:(1) The properties of milled powders are obviously influenced by the pa-rameters of milling process. Under the optimum conditions when the liq-uid-to-balls-and-powders ratio, ball-to-powders ratio, milling speed and milling time are 2:1, 10:1,400r/rain and 40h respectively. The particle size of milled pow-ders with quasi-sphere shape and multi-crystal structures could reach to about 180 nm. The milling refine process can be divided into 3 steps according as milling time. The nanocomposite powders is consolidated with high density at low temperature, the reason for that fine particles with high diffusion coefficient and surface energy, and the impurity of Fe, Ni introduced by high energy ball milling activate the sitering process. The relative density, flexural strength and fracture toughness of composites reach to 98.6%, 681 MPa and 6.24 MPa.m^1/2 respectively prepared un-der the optimal process parameters of 1700℃, 30 MPa for 60 min.(2) Nano-TiC_p dispersion strengthened ultra-fine grained W matrix compos-ites with high density were prepared by ball milling and VHP. The Nano-TiC_p whose content is less than lwt% is dispersed in W matrix uniformly and the size of nano-TiCp is about 100nm after sintering. The incorporation of nano-TiC_p, whose optimal content is lwt%, obviously improves the mechanical properties of the ul-tra-fine grained composites. The relative density, Vickers microhardness, elastic modulus and fracture strength of W-lwt%TiC was 98.4%, 4.33GPa, 396GPa and 1065MPa respectively. The strengthening mechanisms of composites are grain re-fining and boundary strengthening.(3) After high heat load test at heat load flux of 4MW/m², the surface of W-10%TiC is ablated seriously, the grain with quasi-sphere shape is growing and mechanical properties are decreasing obviously. But the surface of W-0.5wt%TiC and W-lwt%TiC is ablated slightly. After high heat load test at heat load flux of 6MW/m², the surface of both W-0.5wt%TiC and W-lwt%TiC is ablated, and the ablation of W-0.5wt%TiC is more seriously than that of W-lwt%TiC. A large number of spherical grains appear in the W-0.5wt%TiC, but few appear in the W-lwt%TiC. The flexural strength of both composites decreases greatly, and the Vickers microhardness changes slightly. Comparatively, W-lwt%TiC composite is proved to have the best high heat load properties.