Thermal fatigue testing of coatings for fusion reactor applications

Abstract Thermal fatigue testing was performed on eight coated or clad materials which have potential application as limiters in pulsed tokamak fusion devices. They are (1) chemically vapor-deposited coatings of TiC, TiB 2 and boron on graphite, (2) plasma-sprayed TiB 2 on copper, (3) a chemical conversion coating of VB 2 on vanadium-clad copper, (4) titanium-clad copper and (5) vanadium-clad copper. Testing consisted of up to 1000 cycles of electron beam heating for 1.5 s at beam power densities of 1 and 2 kW cm −2 . Three materials, chemically vapor-deposited TiC and TiB 2 on graphite, and plasma-sprayed TiB 2 on copper, survived the 1000 cycle 2 kW cm −2 test with slight but acceptable damage. The most notable test failure was VB 2 on vanadium-clad copper which deformed severely by a thermal ratcheting mechanism and displayed subsurface melting.