| Tungsten is a promising candidate material as a plasma facing material (PFM) in ITER due to its highest melting point, low sputtering yield, and good thermal properties. When used in a fusion reactor, PFMs must be joined with heat sink materials to make up of PFC (plasma facing components). Therefore, the advanced tungsten coating technology is very significant for the development of fusion reactor. This research has prepared PFMs (tungsten) by electrodepositing tungsten coatings with different thickness on cooper alloy (CuCrZr), which has been selected as a heat sink material. The preparation technology, crystal structure and physical properties were also investigated in this paper. The main results has been summarized as followings:(1) The tungsten coatings were prepared on CuCrZr alloy substrate by galvanostatic electrolysis in Na2WO4-WO3molten salt with duration from1.5h to30h. The results demonstrated that with the duration increasing, the tungsten grain size and tungsten coatings’thickness were raised, but the surface of tungsten coatings became nonuniform and the current efficiency was decreased. The Vickers micro-hardness and oxygen content of tungsten coatings were decreased with the duration increasing.(2) The tungsten coatings with body-centered cubic (BBC) structure could be eletrodeposited using direct current and pulse current in Na2WO4-WO3molten salt. The effects of direct and pulse current on the structures and performances of tungsten coatings were investigated in this paper. The two tungsten coatings and copper alloy substrates exhibited excellent interface bonding with no evidence of cracks and voids. The pulse electrodeposition could be favorable for controlling the thickness, grain size and the mechanical properties of coatings.(3) A tungsten coating with the thickness of1mm was obtained by pulse electreodeosition when the duration was150h in Na2WO4-WO3melt. The properties of the tungsten coating on copper alloy substrate were investigated. The bonding strength between tungsten coating and copper alloy susbtrate was near60MPa; the thermal conductivity parallel to the crystal growth direction was measured to be150.86W·m-1· K-1. The results of irradiation experiment in Experimental Advanced Superconducting Tokamak indicated that the thick tungsten coating obtained by pulse electreodepsotion had a good irradiation resistance(4) The strength of CuCrZr alloy was measured before and after electro deposition. The results revealed that the strength of CuCrZr alloy was reduced by the process of electro deposition in molten slat. The CuCrZr alloy after electroplating and tungsten coating were treated by aging process for12h at the temperature of703K. After aging treatment, the strength of CuCrZr alloy could be improved to meat the standard in ITER. And the changes in the thermal conductivity and bonding strength of tungsten coating could be negligible.(5) Pure tungsten coating with body-centered cubic (bbc) structure were successfully electrodeposited from Na2WO4-WO3-NaPO3molten salt at1153K in atmosphere. And the addition of NaPO3had an obviously influence on the decrease of tungsten’s grain size. With increasing of current density from50to80mA·cm-2, the grain size of the tungsten coating increased from7.01μm to12.44μm. With the increase of the current density, the thickness of the coating changed from25.92μm.to34.40μm, and then dropped to29.72μm. The results indicated that the thickness and microstructure of tungsten coatings could be improved by adjusting direct current electreodeposition parameters(6) Metallic tungsten coating was successfully obtained as the NaPO3concentration is30mol%at the temperature of1073K. The grain size of coating showed the tendency of decrease with increasing of the content of NaPO3. With the increasing of temperature, the grain size of tungsten coatings increased. When pulse current was set to40-60mA·cm-2, duty cycle was set to0.1-0.25and period was10ms, the excellent surface morphology of tungsten coating was obtained. |
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