Abstract
In order to protect steels from oxidation and corrosion under steam- and fire-side exposures for the next generation of steam turbines, different protective coatings (slurry Al, pack Al, thermal spray CoNiCrAlY, HIPIMS CrN/NbN, sol–gel Al2O3/AlPO4) were assessed on ferritic–martensitic P92 and austenitic HR3C steels. Cyclic oxidation in air at 650 and 700 °C was subsequently conducted for the coatings to grow oxide scales. The thermal transport properties of both the as-deposited and the oxidised coatings were investigated by laser flash analysis till 900 °C to ascertain whether they exhibited any potential harmful insulation to the underlying steel substrate. The results indicated that neither the coatings nor their oxides had any impact on the thermal diffusivity in the temperature range of interest. The thermal diffusivity values were mostly dictated by those of the substrate. It is thus expected that the influence on the thermal transport properties of the coatings under steam conditions will be equivalent than in air.
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