Oxidation of Metals

, Volume 40, Issue 1–2, pp 109–118 | Cite as

Application of a counter-current gaseous diffusion model to the oxidation of hafnium carbide at 1200 to 1530°C

  • G. R. Holcomb
  • G. R. St. Pierre
Article

Abstract

A counter-current gaseous diffusion model is presented to describe the oxidation of hafnium carbide between 1200 and 1530°C. The model separates the porous hafnia scale into two gas diffusion regions separated by a flame front, where O2and CO react to form CO2.In the outer region, O2and CO2counter-diffuse; in the inner region, CO2and CO counter-diffuse. The concentration gradients of each gaseous specie in the pores of the hafnia are determined and the rate of oxidation is calculated. A porosity of 2% and a pore radius of 0.01 μm are representative of the values observed in hafnia during the early stages of HfC oxidation. These values lead to predictions of parabolic rate constants that are close to those measured by thermogravimetric analysis. In addition, the predicted and measured parabolic rate constants are shown to have the same dependence upon temperature and oxygen partial pressure.

Key words

oxidation gaseous diffusion hafnium carbide hafnia porosity 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    G. R. Holcomb, Ph.D. thesis, The Ohio State University (1988).Google Scholar
  2. 2.
    J. T. Prater, Modification of Hafnium Carbide for Enhanced Oxidation Resistance Through Additions of Tantalum and Praseodymium, Air Force Report AFWAL-TR-88-4141, 1988.Google Scholar
  3. 3.
    E. L. Courtright, J. T. Prater, G. R. Holcomb, G. R. St. Pierre, and R. A. Rapp,Oxid. Met. 36, 423–437 (1991).Google Scholar
  4. 4.
    K. Schwerdtfeger and E. T. Turkdogan, inPhysicochemical Measurements in Metals Research (Vol. 4, Part I, Chap. 4B), R. A. Rapp, ed. (1970), pp. 321–407.Google Scholar
  5. 5.
    R. B. Evans, G. M. Watson, and E. A. Mason,J. Chem. Phys. 35, 2076 (1961).Google Scholar
  6. 6.
    J. H. Kim, J. A. Ochoa, and S. Whitaker,Trans. Porous Media 2, 327–356 (1987).Google Scholar
  7. 7.
    J. Bernstein and T. B. Koger,J. Electrochem. Soc. 8, 2086–2090 (1988).Google Scholar

Copyright information

© Plenum Publishing Corporation 1993

Authors and Affiliations

  • G. R. Holcomb
    • 1
  • G. R. St. Pierre
    • 1
  1. 1.Department of Materials Science and EngineeringThe Ohio State UniversityColumbus

Personalised recommendations