Long-Term Corrosion Tests of Prototypical SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) Coatings

Abstract

An iron-based amorphous metal with good corrosion resistance and a high absorption crosssection for thermal neutrons has been developed and is reported here. This amorphous alloy has the approximate formula 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 is known as SAM2X5. Chromium (Cr), molybdenum (Mo) and tungsten (W) were added to provide corrosion resistance, while boron (B) was added to promote glass formation and the absorption of thermal neutrons. Since this amorphous metal has a higher boron content than conventional borated stainless steels, it provides the nuclear engineer with design advantages for criticality control structures with enhanced safety.15-17 While melt-spun ribbons with limited practical applications were initially produced, large quantities (several tons) of gas atomized powder have now been produced on an industrial scale, and applied as thermal-spray coatings on prototypical half-scale spent nuclear fuel containers and neutron-absorbing baskets. These prototypes and other SAM2X5 samples have undergone a variety of corrosion testing, including both salt-fog and long-term immersion testing. The modes and rates of corrosion have been determined in the various environments, and are reported here. While these coatings have less corrosion resistance than melt-spun ribbons and optimized coatings produced in the laboratory, substantial corrosion resistance has been achieved.

Maximizing the Glass Fraction in Iron-Based High Velocity Oxy-Fuel Coatings

“…The ability to develop new iron-based material formulations, such as SAM2X5, which, when applied as a coating, exhibits equivalent or, in some cases, superior corrosion resistance than wrought nickel-based superalloys, involves optimizing all of these key factors. [1][2][3][4][5][6] The chemistry of the coating and its ability to develop an inherently stable protective oxide layer that is nonspalling is paramount to achieving high corrosion resistance. By the use of favorable alloying elements, which preferentially migrate and form in the oxide layer, the protective nature of the oxide that is formed can be altered and optimized.…”

Effect of Oxidation and Crystallization on Pitting Initiation Behavior of Fe-Based Amorphous Coatings

“…Owing to their excellent corrosion resistance and low material cost, Fe-based amorphous coatings offer considerable potential for industrial application in fields such as the military, nuclear power, oil and gas, and manufacturing. Farmer [1,2] attempted to apply Fe-based amorphous coatings on containers used for the transportation, aging, and disposal of spent nuclear fuel and high-level radioactive wastes. The in-transmission neutron absorption cross section for thermal neutrons of Fe 49.7 Cr 17.7 Mn 1.9 Mo 7.4 W 1.6 B 15.2 C 3.8 Si 2.4 (SAM2X5) with a high boron content is four times greater than that of borated stainless steel, and twice as that of nickel-based alloy (C-4) with added Gd.…”