Zr Alloy Substrate Research Articles

Development of cold spray process for oxidation-resistant FeCrAl and Mo diffusion barrier coatings on optimized ZIRLO™

The cold spray process has been investigated for the deposition of FeCrAl coatings on optimized ZIRLO™ fuel cladding tubes in order to enhance oxidation resistance at high temperatures (>1000 °C) that would be encountered in loss of coolant accident (LOCA) scenarios. The FeCrAl alloy provides excellent oxidation resistance, however Fe forms a eutectic with Zr at temperatures as low as 928 °C resulting in massive inter-diffusion and associated melting. Therefore, a Mo interlayer coating was developed also using the cold spray process to serve as a diffusion barrier between the Fe-based coating and the Zr-alloy substrate. To achieve a combination of desired properties for the dual-layered coating-substrate, an optimization study of spray parameters such as propellant gas pre-heat temperature, helical spray speed, and the number of spray passes was conducted. This parametric study was aimed at achieving dense coatings with desired thickness and coverage of the substrate, and good adhesion of the Mo interlayer coating with subsequent top FeCrAl coating and the Zr-alloy substrate. The optimal FeCrAl-Mo coating protected the Zr-alloy cladding tubes from oxidation at high temperatures of 1200 °C, while at the same time preventing diffusion-induced eutectic melting in the substrate.

High Temperature Oxidation Property of SiC Coating Layer Fabricated by Aerosol Deposition Process

AbstractThis study investigated the high temperature oxidation property of SiC coated layer fabricated by aerosol deposition process. SiC coated layer could be successfully manufactured by using pure SiC powders and aerosol deposition on the Zr based alloy in an optimal process condition. The thickness of manufactured SiC coated layer was measured about 5 μm, and coating layer represented high density structure. SiC coated layer consisted ofα-SiC andβ-SiC phases, the same as the initial powder. The initial powder was shown to have been crushed to the extent and was deposited in the form of extremely fine particles. To examine the high temperature oxidation properties, oxidized weight gain was obtained for one hour at 1000°C by using TGA. The SiC coated layer showed superior oxidation resistance property than that of Zr alloy (substrate). The high temperature oxidation mechanism of SiC coated layer on Zr alloy was suggested. And then, the application of aerosol deposited SiC coated layer was also discussed.

Nano/micro tribological behaviors of a self-assembled graphene oxide nanolayer on Ti/titanium alloy substrates

In this study, reduced graphene oxide (RGO) layer is prepared on a self-assembled monolayer (SAM) of 3-aminopropyltriethoxysilane (APTES) modified surface of deposited Ti substrates or Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy substrate. The surface morphology was measured by SEM and AFM. Tribological behaviors in nano scale by AFM and in micro scale by UMT-2 were investigated and compared with titanium substrate, APTES SAM and GO-APTES nanolayer. XPS, water contact angle (WCA) and ellipsometry tests were carried out as assistant methods to discuss the tribological mechanisms. In both nano and micro scale tribological tests, the prepared film holds remarkable tribological properties. It also shows good anti-wear performance in our designed bio-tribological test. Nano and micro tribological mechanisms of the film are discussed.

Electroless Ni-P plating on Mg-10Gd-4.8Y-0.6Zr magnesium alloy with a new pretreatment process

A new pretreatment process for electroless Ni-P plating on Mg-10Gd-4.8Y-0.6Zr was investigated in this paper. The morphology, component, chemical composition and structure of the pretreatment layers and Ni-P coating were analyzed by scanning electronic microscopy, energy dispersive spectroscopy and X-ray diffraction spectroscopy. The structure of Ni-P coating was also detected by transmission electron microscopy (TEM). Potentiodynamic polarization analysis and salt spray test were used to test the corrosion resistance of the Ni-P coating. Experimental results indicate that: metal Cr generated in the new pretreatment process, which provided active points for later zinc immersion process, was beneficial to nickel deposition. The subsequent Ni-P coating was amorphous, in which the content of P was 9.43wt.%. It was uniform and its thickness reached about 50μm at 2h deposition. Compared to Mg-10Gd-4.8Y-0.6Zr alloy substrate, the corrosion potential of the coated alloy shifted by 1090mV positively and the corrosion current density decreased one order of magnitude in 3.5wt.% NaCl solution. The salt spray test time of Ni-P coating was 210h. All of these results suggest that the electroless nickel plating procedure researched in this paper is suitable for Mg-10Gd-4.8Y-0.6Zr alloy.

Incorporation of gadolinium and boron into Zirconium alloy: Surface alloying of immiscible materials using an intense pulsed ion beam

We investigate the potential for incorporation by surface alloying of two elements, gadolinium (Gd) and boron (B), into Zr-alloy substrates, by the application of an intense ion beam pulse to a conventionally pre-applied Gd or B thin film coating to the substrate. The beam is produced by the Repetitive High Energy Pulsed Power-1 (RHEPP-1) ion beam facility at Sandia National Laboratories. Surface alloying is desirable in this case for two reasons: (1) conventional alloying is not possible because both Gd and B have negligible solubility in Zr at room temperature, and (2) a conventionally applied coating without surface alloying may be expected to delaminate in the harsh end-environment where the elements are used (e.g. fission reactors). While surface alloying has been a topic of investigation both by the present and prior researchers, the goal of the present work is the detailed study incorporating heat flow simulations and a full complement of materials analysis tools to characterize surface alloying of Zr-alloy substrates with Gd and B. Use of code simulations is essential for predicting appropriate film thickness and ion beam treatment fluences, which are specific to a given film-substrate system. Characterization after ion beam surface treatments confirmed successful alloying of both Gd and B by significant extension of their solid solubility in Zr-alloy substrates. While Gd surface alloying of Zr-alloys resulted in unacceptable oxidation in thermal and environmental conditions mimicking a nuclear reactor environment, B surface alloying resulted in acceptable corrosion resistance comparable to the as-received Zr-alloys.

Oxide Glass/Amorphous Metal Alloy Laminated Membrane for Hydrogen Separation

Abstract A five-layered membrane composed of an amorphous Ni–Nb–Zr alloy substrate (ca. 30 μm), thin proton–electron mixed conductive tungsten phosphate glass films (ca. 50 nm) and Ni coatings (ca. 20 nm) was fabricated by pulsed laser deposition and vacuum evaporation. A flux of hydrogen passed through the laminated membrane without Pd at 673 K at ca. 2×10−6 mol·cm−2·s−1, and no degradation was observed in the 10 h operation. The present results suggest that amorphous Ni–Nb–Zr alloy passivated with WO3-based oxide glass is a promising material for H2 filtering in a medium temperature range.

Characterization of micro-arc ceramic coatings on Ti-2Al-2.5Zr alloy substrates

Titanium oxide coatings were synthesized on Ti-2Al-2.5Zr alloy substrates by micro-arc oxidation (MAO) technique. The surface features of the coatings were studied by scanning electron microscopy. The micro-arc discharge channels of the Ti-2Al-2.5Zr alloy decrease while the discharge channel size increases clearly with an increase in treating time. With an increase of the coating thickness the porous layer thickness increases apparently. Phase composition of the surface layers of the coatings was evaluated by X-ray diffraction and X-ray photoelectron spectroscopy. The results of XRD and XPS analysis show that the MAO coating mainly consists of anatase and rutile TiO 2.

Optimisation and characterisation of tungsten thick coatings on copper based alloy substrates

Tungsten is a promising armour material for plasma facing components of nuclear fusion reactors because of its low sputter rate and favourable thermo-mechanical properties. Among all the techniques able to realise W armours, plasma spray looks particularly attractive owing to its simplicity and low cost. The present work concerns the optimisation of spraying parameters aimed at 4–5mm thick W coating on copper–chromium–zirconium (Cu,Cr,Zr) alloy substrates. Characterisation of coatings was performed in order to assess microstructure, impurity content, density, tensile strength, adhesion strength, thermal conductivity and thermal expansion coefficient. The work performed has demonstrated the feasibility of thick W coatings on flat and curved geometries. These coatings appear as a reliable armour for medium heat flux plasma facing component.