W/Ta cold spray coatings as an armour layer for first wall steel components

• Thick (1–2 mm) W/Ta coatings were successfully deposited on a steel substrate. • The W/Ta coatings survive power loads up to 20 MW/m² as long as the surface temperature does not exceed 1000 °C. • At higher surface temperatures the coating starts to delaminate typically at weak areas (tile edges and surface contaminations of the substrate). Cold spray could provide a simple and cost-effective method for coating large areas of plasma facing components regardless of their shape. Low local power deposition and the possibility to perform the process under ambient pressure are favorable features of this technology. In initial cold spray coating tests with pure tungsten, no pore-free coatings could be achieved, but trials with a mixture of W and Ta showed rather good results, resulting in dense coatings with a thickness of up to 2 mm on steel with a W content of up 70 %. In this contribution the initial high heat flux tests were expanded towards systematic studies of the coating behaviour under slow transient loads of up to 20 MW/m² and surface temperatures up to 1200 °C. As a result, it could be shown that the coatings survive cyclic loading up to surface temperatures of 1000 °C even under the highest heat loads of 20 MW/m² without any damage or surface modification.