High heat flux resilience of Low-pressure plasma sprayed tungsten coatings for fusion

Tungsten has been identified as baseline plasma-facing material for future fusion devices, such as ITER and DEMO while Eurofer97 is considered a potential primary candidate for structural applications. The complete replacement of damaged or eroded tungsten plasma-facing components requires a substantial investment of time and financial resources, thus highlighting the importance of efficient repair options. Low-pressure plasma spraying (LPPS) is a process with unique characteristics that allows the deposition of dense and high-quality coatings in a short time, and is therefore considered a suitable repair method candidate. In the present study, 300 μm-thick LPPS coatings were applied to Eurofer97 substrates and tungsten substrates, respectively. These coating systems were brazed onto CuCrZr cooling structure and in two experiments exposed to high heat fluxes (HHFs) of up to 4 MW m −2 for Eurofer97 substrates and 18 MW m −2 for tungsten substrates with 200 pulses each. The response was compared to that of an ITER specification fulfilling reference tungsten sample that had been exposed similarly. The in-situ and the subsequent post-mortem analysis of the LPPS tungsten on Eurofer97 substrates revealed only minor material degradation and a performance similar to the reference tile. The LPPS coatings on tungsten substrates exhibited structural changes, with recrystallization occurring in the top 2.8 mm for non-overheating samples, while the reference sample recrystallized to a depth of 3.6 mm. Moreover, the LPPS coatings exhibited lower surface roughening than the reference sample. The LPPS coatings and the interface of coating and substrate were found to be intact. Consequently, the coating system exhibits a suitable performance under high heat flux tests and should be further investigated for fusion applications.