Thermal shock performance of CVD tungsten coating at elevated temperatures

Thick tungsten coating was produced by chemical vapour deposition (CVD) at a high deposition rate 0.6 mm/h. High heat flux tests using electron beam were performed to evaluate the thermal shock resistance of the developed CVD tungsten coating. The polished CVD tungsten surfaces were exposed to single shot disruption-like and repetitive ELM-like thermal shock loads at various temperatures and absorbed power densities. The thermal shock-induced damages were analysed by surface roughometer, scanning electron microscopy and light microscopy. Damage characteristics of the CVD tungsten were compared to that of the reference hot-rolled pure tungsten. The cracking thresholds and damage mechanisms of the CVD tungsten were presented and discussed. The tested results show that specific columnar grain structure of the CVD tungsten and base temperatures have significant influence on the crack formation and propagation direction towards the bulk material.