Infrared characterization and high heat flux testing of plasma sprayed layers

Four series of plasma sprayed actively cooled mock-ups have been evaluated by infrared measurements and heat flux testing. Infrared characterization showed heat transfer capability of the plasma sprayed layer bonded to the substrate. Even if the thermal conductivity of the B4C plasma sprayed coating is only 5% of the bulk material, the coating can easily survive 1000 cycles at 7.5 MW/m2 if the thickness is less than 150 μm. Thick tungsten coatings (3–5 mm) were more fragile, depending on the plasma spray technology. The highest heat flux acceptable for 1000 cycles is 4 MW/m2 with a vacuum plasma spray coating and a Ni–Al–Si–W precoating, accounting for a reduction in the thermal conductivity by a factor of 3.