A High-Performance Corrosion-Resistant Iron-Based Amorphous Metal - The Effects of Composition, Structure and Environmen
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0985-NN08-03
A High-Performance Corrosion-Resistant Iron-Based Amorphous Metal - The Effects of Composition, Structure and Environment on Corrosion Resistance J. Farmer1, J. Haslam1, D. Day1, T. Lian1, C. Saw1, P. Hailey1, J-S. Choi1, R. Rebak1, N. Yang2, R. Bayles3, L. Aprigliano4, J. Payer5, J. Perepezko6, K. Hildal6, E. Lavernia7, L. Ajdelsztajn7, D. Branagan8, and B. Beardsley9 1 Lawrence Livermore National Laboratory, Livermore, CA, 94550 2 Sandia National Laboratory, Livermore, CA, 94550 3 Naval Research Laboratory, Washington, DC, 20375 4 Consultant, Berlin, MD, 21811 5 Case Western Reserve University, Cleveland, OH, 44106 6 University of Wisconsin, Madison, WI, 53706 7 University of California, Davis, CA, 95616 8 The NanoSteel Company, Idaho Falls, ID, 83402 9 Caterpillar, Peoria, IL, 61656
ABSTRACT The passive film stability of several Fe-based amorphous metal formulations have been found to be comparable to that of high-performance Ni-based alloys, and superior to that of stainless steels, based on electrochemical measurements of the passive film breakdown potential and general corrosion rates. Chromium (Cr), molybdenum (Mo) and tungsten (W) provide corrosion resistance; boron (B) enables glass formation; and rare earths such as yttrium (Y) lower critical cooling rate (CCR). The high boron content of this particular amorphous metal also makes it an effective neutron absorber, and suitable for criticality control applications, as discussed in companion publications. Corrosion data for SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) is discussed here. INTRODUCTION The outstanding corrosion resistance possible with amorphous metals has been recognized for many years [1-3]. A number of other iron-based amorphous metals have been published, including several with very good corrosion resistance. Examples include: thermally sprayed coatings of Fe-10Cr-10-Mo-(C,B) which were explored as early as 1996 by Kishitake et al. [4]; bulk Fe-Cr-Mo-C-B [5], and Fe-Cr-Mo-C-B-P [6]. These authors have corroborated the corrosion resistance of the amorphous Fe-Cr-Mo-C-B-P alloys. Nickel-based amorphous metals have also been developed which exhibit exceptional corrosion performance in acids [7]. Several Fe-based amorphous metal formulations have been found that appear to have very good corrosion resistance, based on measurements of the passive film breakdown potential, the corrosion rate and performance during salt fog testing [8-12]. These formulations use chromium (Cr), molybdenum (Mo), and tungsten (W) to provide corrosion resistance, boron (B) to enable glass formation, and yttrium (Y) to lower the critical cooling rate (CRR). SAM1651 (Fe48.0Cr15.0Mo14.0B6.0C15.0Y2.0) has a nominal elemental composition similar to that of the Y-
containing Fe-based amorphous metal formulation discussed in the literature [13-15]. This material has a low critical cooling rate of ~80 Kelvin per second due to the addition of yttrium. A corrosion resistant Fe-based amorphous metal with high boron content is discussed here. The high boron co
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