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Application of Volatility Diagrams for Investigating Dry Etching Reactions of Chromium Oxide in LTCSS Processing

Hsieh, Man-Ching
http://rave.ohiolink.edu/etdc/view?acc_num=case1307497361

Abstract Details

2011, Master of Sciences, Case Western Reserve University, Materials Science and Engineering.
Low-temperature colossal supersaturation (LTCSS) is a diffusional surface hardening process that provides a uniform and conformal hardened gradient surface on austenitic stainless steels. The treatment retains the austenitic phase. In addition, because parts are treated at low temperature, they do not distort or change dimensions. To make the process work, the naturally forming Cr2O3 passive layer on the stainless steel has to be removed to “activate” the surface for carburization. Without this activation step, carbon diffusion into the surface is blocked. This is solved by placing the steel in an atmosphere of gaseous HCl, which removes the Cr2O3 from the surface. The passive film reactions with gaseous HCl atmosphere importantly influence the effectiveness of the following diffusion process, and thus we should investigate the detailed reactions during the activation step. The present work makes use of volatility diagrams for understanding all possible etching reactions in the Cr-O and Cr-Cl system. The results show three effective methods for etching Cr2O3(c): (1) atomic hydrogen (0.1-0.0001bar) can etch Cr2O3(c) effectively at 373-673K. (2) hydrogen chloride gas (at around 1bar) can etch Cr2O3(c) effectively only when the temperature is higher than about 473K. (3) CrO3(c) can be etched more effectively than Cr2O3(c) in a HCl environment. Thus, we can oxidize Cr2O3(c) into CrO3(c) by ozone or atomic oxygen and then etch CrO3(c) in a HCl environment to achieve a higher etching rate.
Arthur Heuer (Committee Chair)
Mark DeGuire (Committee Member)
Gary Michal (Committee Member)
Materials Science

Recommended Citations

Citations

  • Hsieh, M.-C. (2011). Application of Volatility Diagrams for Investigating Dry Etching Reactions of Chromium Oxide in LTCSS Processing [Master's thesis, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1307497361

    APA Style (7th edition)

  • Hsieh, Man-Ching. Application of Volatility Diagrams for Investigating Dry Etching Reactions of Chromium Oxide in LTCSS Processing. 2011. Case Western Reserve University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1307497361.

    MLA Style (8th edition)

  • Hsieh, Man-Ching. "Application of Volatility Diagrams for Investigating Dry Etching Reactions of Chromium Oxide in LTCSS Processing." Master's thesis, Case Western Reserve University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1307497361

    Chicago Manual of Style (17th edition)

case1307497361
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© 2011, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.