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Title: Performance of Al-Rich Oxidation Resistant Coatings for Fe-Base Alloys

Abstract

Aluminum-rich coatings made by chemical vapor deposition and pack cementation on ferritic (e.g. Fe-9Cr-1Mo) and austenitic (Type 304L) substrates are being evaluated at 650-800 C. For oxidation testing, a humid air environment was used to quantify coating performance, as uncoated substrates experience rapid oxidation at these temperatures. A main goal of this work is to demonstrate the potential benefits and problems with alumina-forming coatings. The higher exposure temperatures were selected to accelerate the degradation of the coating by interdiffusion with the substrate. A general conclusion of this testing was that coatings with less Al and a ferritic Fe(Al) structure could be more durable than higher Al content aluminide coatings which have a large thermal expansion mismatch with these substrates. A lifetime model has been developed using diffusion and oxidation observations to predict coating performance as a function of temperature and initial coating composition. To test and improve the model, additional experiments are now being conducted to determine the effect of substrate composition (e.g. Cr content using Fe-12Cr and Fe-9Cr-2W substrates) and exposure temperature on the critical Al content for coating failure. Because of the unexpectedly low level of Al measured at coating failure ({approx}3.5at.% at 700 C), exposures of specimensmore » with thick ({approx}200 {micro}m) high Al content coatings were stopped after 10kh at 800 C and 20kh at 700 C because extremely long times to failure were predicted. Post-exposure Al concentration profiles for these specimens were measured using electron microprobe.« less

Authors:
 [1];  [2]
  1. ORNL
  2. Tennessee Technological University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
FE USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
964714
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 2009 Annual Fossil Energy Material Meeting, Pittsburgh, PA, USA, 20090512, 20090514
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AIR; ALLOYS; CHEMICAL VAPOR DEPOSITION; COATINGS; DIFFUSION; ELECTRONS; LIFETIME; OXIDATION; PERFORMANCE; SUBSTRATES; TESTING; THERMAL EXPANSION; Coatings; oxidation; aluminides; water vapor; ferritic steel

Citation Formats

Pint, Bruce A, and Zhang, Ying. Performance of Al-Rich Oxidation Resistant Coatings for Fe-Base Alloys. United States: N. p., 2009. Web.
Pint, Bruce A, & Zhang, Ying. Performance of Al-Rich Oxidation Resistant Coatings for Fe-Base Alloys. United States.
Pint, Bruce A, and Zhang, Ying. Thu . "Performance of Al-Rich Oxidation Resistant Coatings for Fe-Base Alloys". United States.
@article{osti_964714,
title = {Performance of Al-Rich Oxidation Resistant Coatings for Fe-Base Alloys},
author = {Pint, Bruce A and Zhang, Ying},
abstractNote = {Aluminum-rich coatings made by chemical vapor deposition and pack cementation on ferritic (e.g. Fe-9Cr-1Mo) and austenitic (Type 304L) substrates are being evaluated at 650-800 C. For oxidation testing, a humid air environment was used to quantify coating performance, as uncoated substrates experience rapid oxidation at these temperatures. A main goal of this work is to demonstrate the potential benefits and problems with alumina-forming coatings. The higher exposure temperatures were selected to accelerate the degradation of the coating by interdiffusion with the substrate. A general conclusion of this testing was that coatings with less Al and a ferritic Fe(Al) structure could be more durable than higher Al content aluminide coatings which have a large thermal expansion mismatch with these substrates. A lifetime model has been developed using diffusion and oxidation observations to predict coating performance as a function of temperature and initial coating composition. To test and improve the model, additional experiments are now being conducted to determine the effect of substrate composition (e.g. Cr content using Fe-12Cr and Fe-9Cr-2W substrates) and exposure temperature on the critical Al content for coating failure. Because of the unexpectedly low level of Al measured at coating failure ({approx}3.5at.% at 700 C), exposures of specimens with thick ({approx}200 {micro}m) high Al content coatings were stopped after 10kh at 800 C and 20kh at 700 C because extremely long times to failure were predicted. Post-exposure Al concentration profiles for these specimens were measured using electron microprobe.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2009},
month = {1}
}

Conference:
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