Thermal Transport Properties of New Coatings on Steels for Supercritical Steam Power Plants
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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.
KeywordsSteels Coatings Oxidation Thermal diffusivity
The authors gratefully acknowledge the European Union for the funding of FP7 project “POEMA: Production of Coatings for New Efficient and Clean Coal Power Plant Materials” (Grant Agreement No. 310436). Turbocoating, Sheffield Hallam University, BAM and the Chuiko Institute of Surface Chemistry are greatly indebted for supplying the pack Al and CoNiCrAlY, the HIPIMS CrN/NbN and the Al2O3/AlPO4 hybrid sol–gel coatings, respectively.
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