Applications in the Nuclear Industry for Thermal Spray Amorphous Metal and Ceramic Coatings
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INTRODUCTION
THE outstanding corrosion resistance that may be possible with structurally amorphous metals (SAMs) was recognized several years ago.[1–3] Compositions of several iron-based amorphous metals were published, including some with very good corrosion resistance. Examples included thermally sprayed coatings of Fe-10Cr-10-Mo-(C,B), bulk Fe-Cr-Mo-C-B, and Fe-Cr-Mo-C-B-P.[4–6] The corrosion resistance of an iron-based amorphous alloy with yttrium (Y), Fe48Mo14Cr15Y2C15B6 was also established.[7–9] Yttrium was added to this alloy to lower the critical cooling rate. Because nickel-based crystalline materials have excellent corrosion resistance, several nickel-based amorphous metals have also been developed by other researchers and were compared with thermal spray coatings of crystalline materials. Nickel-based amorphous materials exhibited exceptional corrosion performance in acids, and thermal spray coatings of crystalline nickel-based alloy appear to have less corrosion resistance than J. BLINK, J. FARMER, and C. SAW, Doctors, are with the Lawrence Livermore National Laboratory, Livermore, CA 94550. Contact e-mail: [email protected] J. CHOI, formerly with the Lawrence Livermore National Laboratory, Livermore, CA, is Doctor with Tokyo University, Tokyo, Japan. This article is based on a presentation given in the symposium entitled ‘‘Iron-Based Amorphous Metals: An Important Family of High-Performance Corrosion-Resistant Materials,’’ which occurred during the MSandT meeting, September 16–20, 2007, in Detroit, Michigan, under the auspices of The American Ceramics Society (ACerS), The Association for Iron and Steel Technology (AIST), ASM International, and TMS. Article published online April 10, 2009 1344—VOLUME 40A, JUNE 2009
comparable nickel-based amorphous metals.[10] The study reported here focuses on iron-based amorphous metals that have the potential to rival the corrosion resistance of nickel-based crystalline or amorphous materials at significantly lower cost. A family of iron-based amorphous metals with very good corrosion resistance has been developed that can be applied as a protective thermal spray coating. One of the most promising formulations within this family was found to be Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 (SAM2X5), which included chromium (Cr), molybdenum (Mo), and tungsten (W), for enhanced corrosion resistance, and boron (B) to enable glass formation and neutron absorption.[11–15] The parent alloy for this series of amorphous alloys, which is known as SAM40 and represented by the formula Fe52.3Cr19Mn2Mo2.5W1.7 B16C4Si2.5, has less molybdenum than SAM2X5 and was originally developed by Branagan.[16,17] Another similar and promising iron-based SAM material is SAM1651, Fe48Mo14Cr15Y2C15B6.
II.
POSSIBLE APPLICATIONS
The SAM material SAM2X5 may have beneficial application as a neutron absorber, supporting the safe long-term disposal of spent nuclear fuel (Figures 1 and 2). This material has exceptional neutron absorption characteristics and is stable at high dose. The absorption cross secti
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