The focus of this review is the state of knowledge of the oxidation behaviour in steam of alloys with potential for use as pressure parts in steam boilers. The rate of oxide growth on steam-touched surfaces and the characteristics of that oxide are of increasing interest as the quest for improvements in cycle efficiency leads to progressively higher operating temperatures and pressures. The consequences of increased rate of growth of these oxides are of concern because of implications for tube overheating and oxide exfoliation. Mitigation of such problems requires a mechanistic understanding of the influences of alloy composition and microstructure, and especially of the evolution with time of specific scale structures. Similarly, the relative effects of factors such as time, temperature and operating parameters must be understood. The oxidation behaviour of the class of ferritic steels that forms the bulk of the heat transfer surface in steam boilers is of particular importance since allo...

A review of the oxidation behaviour of structural alloys in steam

Abstract Surface-modified zirconium (Zr)-based alloys, mainly by fabricating protective coatings, are being developed and evaluated as accident-tolerant fuel (ATF) claddings, aiming to improve fuel reliability and safety during normal operations, anticipated operational occurrences, and accident scenarios in water-cooled reactors. In this overview, the performance of Zr alloy claddings under normal and accident conditions is first briefly summarized. In evaluating previous studies, various coating concepts are highlighted based on coating materials, focusing on their performance in autoclave hydrothermal corrosion tests and high-temperature steam oxidation tests. The challenges for the utilization of coatings, including materials selection, deposition technology, and stability under various situations, are discussed to provide some valuable guidance to future research activities.

https://www.degruyter.com/downloadpdf/j/corrrev.2017.35.issue-3/corrrev-2017-0010/corrrev-2017-0010.xml

Protective coatings on zirconium-based alloys as accident-tolerant fuel (ATF) claddings

We propose a simple method for the efficient and rapid synthesis of one-dimensional hematite (α-Fe2O3) nanostructures based on electrical resistive heating of iron wire under ambient conditions. Typically, 1–5 μm long α-Fe2O3 nanowires were synthesized on a time scale of seconds at temperatures of around 700 ° ⊂. The morphology, structure, and mechanism of formation of the nanowires were studied by scanning and transmission electron microscopies, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman techniques. A nanowire growth mechanism based on diffusion of iron ions to the surface through grain boundaries and to the growing wire tip through stacking fault defects and due to surface diffusion is proposed.

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Simple and rapid synthesis of α-Fe2O3 nanowires under ambient conditions

Direct combustion of recyclable metal fuels for zero-carbon heat and power

Oxidation of fuel cladding candidate materials in steam environments at high temperature and pressure

The oxidation behaviour of metals and alloys at high temperatures in atmospheres containing water vapour: A review

Offshore oil production with floating platforms and FPSO-type production vessels has grown continuously in the last decades. When in service, the structural elements of these vessels draw a maximum depth of about 20 m meters. Therefore, the need for in situ repairs is within depths of this order and wet welding should be considered as a solution since it has the advantages of simplicity, low cost, and accessibility. This work presents results from a research program whose main objectives were to develop consumables and welding techniques to produce underwater welded joints with structural quality with the shielded metal arc welding process. The experimental results were obtained from joints welded inside a hyperbaric simulator using a mechanized gravity feeding system at depths up to 20 m. The most important result was the development of a class AWS 70XX low alloy Ni-Mo ferritic stick electrode. Good weld metal properties such as elongation, toughness, porosity, and diffusible hydrogen were achieved. The results allowed the prediction of tensile strength, yielding strength, elongation, hardness, and toughness from the Ni, Mo, and Carbon contents. Depth had no significant influence on the mechanical properties and porosity up to 20 m. Field tests with diver-welders at depths of 5 m and 10 m have also been performed. The possibility of producing welded joints that meet the “Class A” requirements of the AWS D3.6M: 2017 code is discussed. 

M. Monteiro

Papers

The oxidation behaviour of metals and alloys at high temperatures in atmospheres containing water vapour: A review

Development of oxyrutile low alloy ferritic electrode for wet welding