Showing papers on "Zirconium alloy published in 2016"

On the mechanical and electrical properties of copper-silver and copper-silver-zirconium alloys deposits manufactured by cold spray

Abstract: In this work, several copper alloy deposits were manufactured by cold spray with helium as accelerating and carrier gas. Electrical conductivity was measured to establish the potential of cold spray as a manufacturing process for high strength (>500 MPa) and high conductivity (>90% IACS) copper alloys. The deposits which are characterized by a low oxygen content (

High-Temperature Oxidation of Zircaloy-4 in Oxygen–Nitrogen Mixtures

Abstract: Isothermal oxidation experiments with cladding tube segments of Zircaloy-4 (Zr-1.3%Sn) in oxygen–nitrogen model mixtures were performed at 800, 1000, and 1200 °C for 6, 1 h, and 15 min, respectively. The gas compositions varied between 0 and 100 vol% nitrogen including 1 and 99 vol%. A strong accelerating effect of nitrogen on the oxidation kinetics was seen for a wide range of boundary conditions. At 800 °C, oxidation in all mixtures with 1–99 % nitrogen resulted in higher reaction rates compared to the pure gases, especially after transition from protective to non-protective oxide scales. At 1000 and 1200 °C, only starvation of oxygen in mixtures with low oxygen contents resulted in lower rates compared to pure oxygen. The oxide scales formed in the mixtures were very porous due to the formation of zirconium nitride at the metal-oxide interface and its oxidation during continuing reaction. The extension of the oxide-nitride zone increased with temperature and with nitrogen content in the gas mixture. Nitrogen seems also to affect the pre-transition reaction kinetics. The mechanism of the faster oxidation kinetics of zirconium alloys in atmospheres containing nitrogen will be discussed in this paper.

A study of the zirconium alloy protection by Cr3C2–NiCr coating for nuclear reactor application

Abstract: The protection of the zirconium alloy by Cr 3 C 2 –NiCr coating has been evaluated. The corrosion resistant carbide-based cermet coatings were deposited on the zirconium alloy substrate using high velocity oxygen fuel technique and were exposed to high-temperature air and steam environment from 700 °C to 1000 °C. To examine the performance of the coating in supercritical water, the coating was tested in autoclave at 400 °C/10.3 MPa for 72 h. The thermal shock experiments were conducted to examine the bonding of the coating. It was suggested that the coating encompassing compatible electronegativity and thermal expansion coefficient with zirconium alloys and favorable toughness could be selected as a candidate for fuel cladding protection layer.

Doping in the Valley of Hydrogen Solubility: A Route to Designing Hydrogen-Resistant Zirconium Alloys

Abstract: Hydrogen embrittlement of metallic alloys is critical to the aging and failure of components in power plants and infrastructure. Embrittlement begins with hydrogen penetrating the protective oxide film that naturally grows on a surface in air. The authors apply concepts from semiconductor defect physics and catalysis to develop materials engineering strategies for thwarting hydrogen uptake. For ZrO${}_{2}$ film on a Zr alloy, a model system that is important for materials in nuclear reactors, they demonstrate that one can use doping to tune the chemical potential of electrons in ZrO${}_{2}$ either to minimize the solubility of hydrogen, or to facilitate its evolution as H${}_{2}$ gas from the surface.

Weld Bead Size, Microstructure and Corrosion Behavior of Zirconium Alloys Joints Welded by Pulsed Laser Spot Welding

Abstract: Pulsed laser spot welding of intersection points of zirconium alloys straps was performed. Weld bead size, microstructure and the corrosion behavior of weld bead were investigated. With the increasing laser peak power or number of shots, the weld width of the beads increased, the protrusion decreased and the dimple increased with further increase in heat input. The fusion zone consisted of a mixture of αZr and residual βZr phases. After annealing treatment, βNb and Zr(Fe, Nb)2 second phase particles were precipitated inter- and intragranular of αZr grains adequately. The oxide thickness of annealed weld bead was about 3.90 μm, decreased by about 18.1% relative to the 4.76 μm of as-welded specimen corroded at 400 °C and 10.3 MPa for 20 days. The corrosion resistance of annealed specimen was better than that of as-welded specimen, since the second phase particles exerted better corrosion resistance, and the content of Nb in βZr and the fraction of βZr decreased after the annealing treatment.

Effect of titanium ion implantation and deposition on hydrogenation behavior of Zr-1Nb alloy

Abstract: In order to study the effect of titanium ion implantation and deposition on hydrogenation behavior of Zr–1Nb alloy, the samples were subjected to plasma immersion implantation and deposition (PIII&D) of titanium ions at the bias voltage of 0.5–1.5 kV using a filtered metal vapor vacuum arc source. The crystalline structure, surface morphology and depth distributions of elements in the surface layer of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and glow-discharge optical emission spectroscopy (GD-OES), respectively. Hydrogen saturation was performed from hydrogen atmosphere at 673 K temperature and 2 atm. pressure. It was found that hydrogen absorption rate by Zr–1Nb alloy decreased after PIII&D. The modified layers contained a mixing zone of titanium and zirconium, which decreases with increasing bias voltage. Hydrogenation causes the formation of titanium hydrides and lattice distortions of α–Zr at the low bias voltage that does not occur at higher bias voltages. The hydrogenation behavior of modified zirconium alloy was discussed.