Erosion of boron carbide coating due to high pulse number transient heat loads

A boron carbide (B₄C) coating, deposited on tungsten using the detonation spraying method, was tested under high pulse number transient heat loads expected during the ITER tokamak H-mode operation. The heat loads were relevant to those caused by edge localized modes (ELMs) and mitigated disruptions. The results showed that in the case of ELM-like heating expected in the first wall zone of the ITER tokamak, the coating is capable to withstand \sim 10^4 pulses before detachment from the substrate. In the case of thermal shocks with more intense heating by mitigated plasma disruptions or ELM-like heating in the divertor zone, the coating detached only after several pulses. The results of the work show that transient heat load is a serious factor limiting the use of B₄C as a plasma-facing material. The use of such ceramic coatings requires the development of ELM and disruption mitigation systems, as well as in situ coating renewal methods.