Zirconium alloy

About: Zirconium alloy is a research topic. Over the lifetime, 6548 publications have been published within this topic receiving 78954 citations. The topic is also known as: zircaloy.

High Temperature Oxidation Behavior of Amorphous Zr–Ni Alloys in Air

Abstract: Oxidation behavior of amorphous Zr 33 Ni 67 and Zr 65 Ni 35 alloy ribbons of ca. 20 μm thickness was studied in air at 800 K by DSC, TGA, XRD and SEM/EDX. It was found that the preferential oxidation of Zr takes place on both Zr-Ni alloys. Zirconium in the alloy was almost completely oxidized with a high oxidation rate before the oxidation of Ni started because of the small alloy thickness. The oxidation process of the pre-crystallized Zr 33 Ni 67 alloy was essentially the same as for the amorphous counter part. The oxidation rate followed the parabolic rate law after the completion of preferential oxidation of zirconium, and the parabolic rate constant was ca. 5.4 x 10 -3 g 2 . m -4 .s -1 . The oxidation of the amorphous Zr 65 Ni 35 alloy had two parabolic stages within the experimental time span up to 18000 s ; the parabolic rate constant was 2.2 x 10 -3 g 2 . m -4 . s -1 in the first stage and 1.02 x 10 -2 g 2 .m -4 .s -1 in the second stage which began by the cracking of the surface film. Oxidation products were ZrO 2 and NiO, metallic nickel remained on both alloys, and Zr 2 Ni and ZrNi, on the Zr 65 Ni 35 alloy within the experimental time span. Tetragonal and monoclinic ZrO 2 were produced. Tetragonal ZrO 2 was major on the Ni-rich alloy, and the monoclinic ZrO 2 on the Zr-rich alloy. Porous cocoon- or worm-like NiO developed on the surface by diffusion of nickel through pinholes and/or cracks of the Zr-enriched protective surface film. Most of the oxidized nickel was, however, embedded inside.

Influence of Environment on the Corrosion of Zirconium and Its Alloys in High‐Temperature Steam

Abstract: Measurements of weight gains and film capacities of Zr and Zr alloys in steam and O at atmospheric and high pressures are reported. At best, the behavior of resistant alloys and of Van Arkel Zr in steam inhibited with boric acid is comparable to that of Van Arkel Zr in O. It was concluded that in steam, but not in O, the pressure drop due to the flow of gas through porous oxide is a significant factor in the effects observed. Alloying elements, and a1so boric acid inhibition, decrease the film cracking or porosity, which, with unalloyed Zr, leads to very rapid corrosion in high-pressure steam. With some more resistant materials there appears to be a compensation effect whereby films formed in high-pressure steam are less porous than those formed at atmospheric pressure. Detailed topographical studies of the early stages of film growth and breakdown on Van Arkel Zr in steam and in O are described. In addition to uniform film growth, at rates varying with grain orientation, rapid localized attack is found in steam. Such attack is accelerated by an increase of pressure and appears to be diminished by additions of Cu and by boric acid inhibition. The localizedmore » corrosion is considered to be due to the same type of film failure as is responsible for cracking or porosity in thicker, more uniform, films at a later stage of corrosion. The implications of the findings for the development of steam-resistant alloys are considered. (auth)« less