Abstract
The oxidation behaviors of Cr, Cr93.4Al6.6, Cr58.1Al41.9, and Cr34.5Al65.5 coatings, deposited by using multi-arc ion plating technology, at high temperature were studied. The weight gain, oxide thickness, morphology, and phase composition of the coatings before and after oxidation were analyzed in detail. The results show that there is an Al content window available for tuning the oxidation behaviors of the CrAl-based coatings. The Cr93.4Al6.6 coating is considered to be most protective and can effectively improve the high-temperature oxidation resistance of the substrate; whereas, too high an Al content has a harmful effect on the antioxidant properties of the coatings. The oxidation mechanism of Cr and CrAl coatings were also discussed.
Highlights
Zr alloy is widely used in fuel cladding due to its superior high-temperature mechanical properties [1,2], high-temperature corrosion resistance, and low thermal neutron absorption cross-section
The Atomic Energy Commission (CEA) in the framework of the French Nuclear Institute, in partnership with AREVA and Electricite De France (EDF), used magnetron sputtering to deposit a Cr coating on the surface of the Zircaloy-4 (Zr-4) substrate, and the samples were oxidized under different high-temperature water vapor environments
Wei et al [14] found that, when a 20 μm Cr coating is oxidized in the air at 800 ◦C, a dense Cr2O3 film is formed on the surface, which has excellent oxidation resistance
Summary
Zr alloy is widely used in fuel cladding due to its superior high-temperature mechanical properties [1,2], high-temperature corrosion resistance, and low thermal neutron absorption cross-section. Zircaloy will oxidize with water/vapor, causing the fuel cladding to fail and producing a large amount of hydrogen [3] that accumulates in the shell mixed with oxygen and air and explodes. This is how the explosion at the Fukushima nuclear power plant in March 2011 came about. The world nuclear industry proposed accident tolerant fuel (ATF), by adding a coating to the surface of the traditional Zircaloy cladding, to improve its resistance to high-temperature water vapor oxidation. The main drawback for high-temperature applications of the aforementioned conventional Cr coatings is their limited oxidation resistance and oxidization to volatile CrO3 above around 1000 ◦C
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