Evaluation of vacuum plasma-sprayed boron carbide protection for the stainless steel first wall of WENDELSTEIN 7-X

To minimize radiation losses of the plasma during long pulse operation, the first wall protection of WENDEL-STEIN 7-X demands low-Z plasma facing materials. In addition to carbon materials on high heat flux loaded components, 300-500 mum thick vacuum plasma-sprayed (VPS) layers of boron carbide (B4C) are considered as coatings on large actively cooled stainless steel panels. In order to evaluate the behaviour relevant to the expected plasma wall interactions, an extensive material characterization and test programme was executed. Also included is the examination of the industrial manufacturing and the suitability of these coatings as 70 m(2) first wall plasma facing material for W7-X. To improve the adhesion of thick B4C layers on stainless steel, different interlayers have been investigated. Based on the results, a VPS-based coating technique was identified which is suitable to manufacture the B4C protection layers on stainless steel wall panels of W7-X. (C) 2004 Elsevier B.V. All rights reserved.