Iron-Based Amorphous Metals: High-Performance Corrosion-Resistant Material Development

Abstract

An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was cosponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the U.S. Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition, materials synthesis, thermal stability, corrosion resistance, environmental cracking, mechanical properties, damage tolerance, radiation effects, and important potential applications. Amorphous alloys identified as SAM2X5 (Fe 49.7 Cr 17.7 Mn 1.9 Mo 7.4 W 1.6 B 15.2 C 3.8 Si 2.4 ) and SAM1651 (Fe 48 Mo 14 Cr 15 Y 2 C 15 B 6 ) have been produced as meltspun ribbons (MSRs), dropcast ingots, and thermal-spray coatings. Chromium (Cr), molybdenum (Mo), and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of MSRs and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently, thermal-spray coatings of these amorphous alloys have been made and subjected to long-term saltfog and immersion tests; good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while the open-circuit corrosion potentials (OCPs) were simultaneously monitored; reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber and suitable for criticality-control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional stainless steel and Ni-based materials, and are proving to have excellent wear properties, sufficient to warrant their use in earth excavation, drilling, and tunnel-boring applications. Large areas have been successfully coated with these materials, with thicknesses of approximately 1 cm. The observed corrosion resistance may enable applications of importance in industries such as oil and gas production, refining, nuclear power generation, shipping, etc.

Mechanical Properties of an Fe‐Based SAM2×5‐630 Metallic Glass Matrix Composite with Tungsten Particle Additions

“…In general, measurements for SAM2Â5-630 are comparable to those of other Fe-based BMGs reported earlier, whose average hardness values were reported to be between 7.5 and 15.9 GPa and modulus values were between 116 and 281 GPa. [5,11,30,31] Higher hardness measurements by nanoindentation compared to Vickers indentation are consistent with our previous results [11] because the effect of material pile-up can cause www.advancedsciencenews.com www.aem-journal.com overestimation of the hardness by up to 50%. [32] However, the overestimate compared to Vickers hardness increases from 33% for SAM2Â5-630 to 176% for SAM2Â5/30%W.…”

“…7 Cr 17.7 Mn 1.9-Mo 7.4 W 1.6 B 15.2 C 3.8 Si 2.4 ) is known for its high corrosion resistance and is reported to be four to five times harder and more wear resistant than stainless steels and nickelbased alloys. [5] Additionally, the high boron content of SAM2Â5 makes it an effective neutron absorber, and suitable for criticality control applications. [5] This amorphous alloy can be applied as thermal spray coatings to protect materials exposed to harsh environments, such as containers used for the long-term storage of spent nuclear fuel.…”

“…[5] Additionally, the high boron content of SAM2Â5 makes it an effective neutron absorber, and suitable for criticality control applications. [5] This amorphous alloy can be applied as thermal spray coatings to protect materials exposed to harsh environments, such as containers used for the long-term storage of spent nuclear fuel. [5] A specific in situ composite of SAM2Â5 (i.e., SAM2Â5-630) has the highest elastic limit during shock impact ever reported for a BMG.…”

“…[5] This amorphous alloy can be applied as thermal spray coatings to protect materials exposed to harsh environments, such as containers used for the long-term storage of spent nuclear fuel. [5] A specific in situ composite of SAM2Â5 (i.e., SAM2Â5-630) has the highest elastic limit during shock impact ever reported for a BMG. [6] Unfortunately, amorphous metals in general suffer from a strong tendency toward shear localization, which leads to low fracture toughness and macroscopically brittle failure at room temperature.…”

The effect of residual stress on the electrochemical corrosion behavior of Fe-based amorphous coatings in chloride-containing solutions

“…These overlapping peaks corroborate the hypothesis that several nanocrystalline phases are present in the amorphous matrix. The XRD diffractogram also suggest that there is a negligible amount of oxides present in the AC-HVAF AMCs, since the oxide phases are known to have a detrimental effect on the formation of the amorphous structure [3]. The crystalline phases present in the AMCs were identified as Fe 2 C, Cr 7 C 3 , M 23 C 6 and Cr 2 B…”