Thermal-shock- and fatigue-resistant coatings for magnetically confined fusion environments

Candidate coating systems of materials of low atomic number Z under development for fusion reactor applications were exposed to a maximum of 1000 cycles of electron beam pulse heating at 2 kW cm -2 for 1.5 s. The coating/substrate systems that we investigated include chemically vapor-deposited TiB 2/graphite, chemically vapor-deposited TiC/graphite, chemically vapor-deposited B/graphite, plasma-sprayed TiB 2/Cu, clad V/Cu, clad Ti/Cu and clad plus borided VB 2/V/Cu. All the thin coatings obtained by chemical vapor deposition (CVD) survived the testing as did the plasma-sprayed TiB 2/Cu. Coatings of CVD TiB 2 and CVD TiC on Poco graphite showed fatigue cracking which may have propagated into the graphite substrates. Some of the clad materials showed failure due to coating melt and deformation and separation due to thermal ratcheting.