Behavior of Tungsten Coated with Boron Carbide Exposed to Intense Plasma Streams

Abstract

To date, the possibility of using a fully tungsten coating of the first wall is being discussed within the ITER project. As a result, the key objectives of the project may not be achieved. Tungsten coatings with boron carbide B₄C having a thickness of no more than 50 µm are considered as one of the possible solutions. This paper describes the results of testing samples of tungsten coated with boron carbide under the action of an intense deuterium plasma stream at the QSPA-T plasma gun. The heat load on the samples reached w_e = 1.4 GW/m² at a pulse duration of 1 ms. During plasma experiments, brittle destruction of boron carbide due to material cracking is observed. This process is accompanied by chipping of the pieces of the coating. Surface swelling is observed for the sample obtained by detonation spraying. Subsequent plasma exposure leads to B₄C destruction and erosion crater formation in places of swelling. Therefore, even at a lower thermal load (1.1 GW/m² instead of 1.4 GW/m²), the B₄C layer deposited on tungsten by detonation spraying erodes more strongly than the B₄C layer deposited by atmospheric plasma spraying.