High heat load properties of high purity CVD tungsten

High heat load experiments using electron beams were carried out to investigate the performance of chemical vapor deposition-tungsten coated molybdenum (CVD-W/Mo) under fusion relevant conditions. Microstructural observation showed that no crack had been formed after 300 shot heat load (23 MW/m2 for 30 s, typical surface temperature: 800 deg. C). The results indicate that the CVD-W/Mo had good thermal fatigue property under the cyclic heat load. Above 1300 deg. C at which the recrystalization would start cracks were formed easily by thermal stress. Crack propagation was apt to be less than that of powder metallurgy tungsten in the temperature range. It is considered that the high purity of CVD-W suppressed the embrittlement due to the recrystallization