Abstracted model for ceramic coating

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Engineers are exploring several mechanisms to delay corrosive attack of the CAM (corrosion allowance material) by dripping water, including drip shields and ceramic coatings. Ceramic coatings deposited with high-velocity oxyfuels (HVOF� s) have exhibited a porosity of only 2% at a thickness of 0.15 cm. The primary goal of this document is to provide a detailed description of an abstracted process-level model for Total System Performance Assessment (TSPA) that has been developed to account for the inhibition of corrosion by protective ceramic coatings. A second goal was to address as many of the issues raised during a recent peer review ... continued below

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Farmer, J C & Stockman, C November 14, 1998.

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Description

Engineers are exploring several mechanisms to delay corrosive attack of the CAM (corrosion allowance material) by dripping water, including drip shields and ceramic coatings. Ceramic coatings deposited with high-velocity oxyfuels (HVOF� s) have exhibited a porosity of only 2% at a thickness of 0.15 cm. The primary goal of this document is to provide a detailed description of an abstracted process-level model for Total System Performance Assessment (TSPA) that has been developed to account for the inhibition of corrosion by protective ceramic coatings. A second goal was to address as many of the issues raised during a recent peer review as possible (direct reaction of liquid water with carbon steel, stress corrosion cracking of the ceramic coating, bending stresses in coatings of finite thickness, limitations of simple correction factors, etc.). During the periods of dry oxidation (T 2 100°C) and humid-air corrosion (T I 100°C & RH < SO%), it is assumed that the growth rate of oxide on the surface is diminished in proportion to the surface covered by solid ceramic. The mass transfer impedance imposed by a ceramic coating with gas-filled pores is assumed to be negligible. During the period of aqueous phase corrosion (T I 100°C & RH > 80%), it is assumed that the overall mass transfer resistance governing the corrosion rate is due to the combined resistance of ceramic coating & interfacial corrosion products. Two porosity models (simple cylinder & cylinder-sphere chain) are considered in estimation of the mass transfer resistance of the ceramic coating. It is evident that substantial impedance to 02 transport is encountered if pores are filled with liquid water. It may be possible to use a sealant to eliminate porosity. Spallation (rupture) of the ceramic coating is assumed to occur if the stress introduced by the expanding corrosion products at the ceramic- CAM interface exceeds fracture stress. Since this model does not account for the possibility of corrosion products filling pores, it is believe to be very conservative. In such a case, the corrosion product would not spread across the ceramic-CAM interface and no spallation would occur. Thus, the coating would be expected to last indefinitely.

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  • Other: DE00004087
  • Report No.: UCRL-ID-132713
  • Grant Number: W-7405-Eng-48
  • DOI: 10.2172/4087 | External Link
  • Office of Scientific & Technical Information Report Number: 4087
  • Archival Resource Key: ark:/67531/metadc686416

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  • November 14, 1998

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  • July 25, 2015, 2:20 a.m.

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  • May 6, 2016, 8:56 p.m.

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Farmer, J C & Stockman, C. Abstracted model for ceramic coating, report, November 14, 1998; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc686416/: accessed December 14, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.