Development and characterization of powder metallurgically produced discontinuous tungsten fiber reinforced tungsten composites

Abstract

In future fusion reactors, tungsten is the prime candidate material for the plasma facing components. Nevertheless, tungsten is prone to develop cracks due to its intrinsic brittleness-a major concern under the extreme conditions of fusion environment. To overcome this drawback, tungsten fiber reinforced tungsten (W f /W) composites are being developed. These composite materials rely on an extrinsic toughing principle, similar to those in ceramic matrix composite, using internal energy dissipation mechanisms, such as crack bridging and fiber pull-out, during crack propagation. This can help W f /W to facilitate a pseudo-ductile behavior and allows an elevated damage resilience compared to pure W. For pseudo-ductility mechanisms to occur, the interface between the fiber and matrix is crucial. Recent developments in the area of powder-metallurgical W f /W are presented. Two consolidation methods are compared. Field assisted sintering technology (FAST) and hot isostatic pressing (HIP) are chosen to manufacture the Wf/W composites. Initial mechanical

Fracture behavior of random distributed short tungsten fiber-reinforced tungsten composites

“…From Figure 7, it can be seen that, for Wf/W material, the force-displacement curves measured by the quantitative 3-point bending system give the same trend as the qualitative 3-point bending results in previous studies [5,7]: after an increasing linear-elastic response, the slope of the load deflection curve changes slightly; then the load further increases with several small load drops;…”

Materials development for new high heat-flux component mock-ups for DEMO

“…Various methods of building and constructing W f /W composites, either via Chemical Vapor Deposition (CVD) [38,39] or powder metallurgical (PM) processes [40,41] are available. Based on the work presented here and previous work [40,42,43,44,45,36,46], the basic proof of principle for CVD & PM-W f /W has been achieved. One of the crucial issues is to maintain as much of the properties of the constituents even after exposing the material to the production cycle and the fusion environment allowing for optimal extrinsic toughening and pseudo-ductile behaviour.…”

“…With respect to the constituent properties it can be expected that when using doped W-wires they will retain their ductility even at elevated temperatures (above 1500 K) [42] and all mechanisms necessary for pseudo-ductility will be enabled [14,43,45]. Properties of the fibres can however be degraded by various circumstances e.g.…”

“…by impurities during fabrication [48,49], high-temperatures or neutron irradiation during operation [30,50]. For the purpose of this paper material produced via (Field Assisted Sintering Technology) FAST as described in [45,46,48] is used. The typical sample size produced is a 40mm disc as depicted in figure 3.…”

Production of tungsten-fibre reinforced tungsten composites by a novel continuous chemical vapour deposition process

“…This limitation is mitigated by using tungsten fibre-reinforced tungsten composites (W f /W) [7,8,9] which utilizes extrinsic mechanisms to improve the toughness similar to ceramic fibre-reinforced ceramics [10]. W fibres made of commercially available W wire (OSRAM GmbH) are used as reinforcements [11,12,13,14] in combination with a tungsten matrix produced either by a chemical deposition [7,15] or by a powder metallurgical process [16,17]. It has been shown that this idea in principle works in as-fabricated state [7,18] as well as after embrittlement [19,20].…”