Observation of the effect of surface roughness on the oxidation of Zircaloy-4

Abstract

a b s t r a c tZirconium alloys are used as fuel cladding in light water reactors. Surface preparation techniques that might impair oxidation resistance would limit the lifetime of the cladding and therefore prevent higher burn-up of fuels. The work presented here investigates the impact of surface roughness on the oxidation kinetics of Zircaloy-4 in 400 • C steam for exposures up to 275 days. The work shows well defined differences in oxidation kinetics between sample preparations following ∼84 days oxidation. Scanning electron microscopy (SEM) and image analysis of samples in cross section allows for an assessment of the variation in surface roughness between samples at different stages of oxidation.

In-situ digital image correlation for fracture analysis of oxides formed on zirconium alloys

“…This work determines the fracture strength of oxides formed thermally on zirconium alloys, and offers a route to investigate other thin films and coatings. It also demonstrates the potential impact of the surface roughness in promoting fracture of the oxide layer, which could reduce the protective nature of the oxide layer [44].…”

“…These include the impact of initial surface roughness [44], interfacial roughness which develops during oxidation [7,[15][16][17]45], and the tetragonal to monoclinic phase transformation [20,46]. These cracks have been directly linked with breakdown of the protective character of the oxide and acceleration in the corrosion kinetics, via the creation of fast ingress routes for oxygen containing species [7,11,12,16,17].…”

Effect of SiO2 Dispersion on Chlorine-Induced High-Temperature Corrosion of High-Velocity Air-Fuel Sprayed NiCrMo Coating

“…Cl -and Cl2 diffuse through the oxide grain boundaries ("electrochemical" mechanism) and oxide's defects ("active-corrosion" mechanism) respectively to reach the coating/oxide scale interface. Vaporization of the metallic chlorides occurs in this step, which leads to formation of the gap at the coating/chloride layer [45]. Fig.…”

“…The previous work performed in an ambient air environment at 600 °C for 168 h indicated that reducing the surface roughness to Ra<0.1 μm resulted in the weight gain of the NiCrMoSiO2 coating being reduced by ~71% compared to the non-polished coating. Such behavior could be attributed to either the higher level of residual stresses (above the roughness peaks) which lead to oxide spallation/cracking, or higher surfcae area exposed to the environment in the as-spryaed coatings [45]. Fig.…”

Peridynamic simulations of the tetragonal to monoclinic phase transformation in zirconium dioxide

“…In oxides formed on zirconium alloys cracks are known to form parallel and close to the metal oxide interface (N. P Platt et al, 2015;P. Platt et al, 2015a), and perpendicular to the metal-oxide interface at higher temperatures (Omar et al, 2015;Parry et al, 2013).…”