Search results for " Corrosion"
showing 10 items of 152 documents
Numerical modelling of the galvanic coupling in aluminium alloys: A discussion on the application of local probe techniques
2010
Abstract A discussion is proposed on the determination of the input values and the experimental validation of finite element modelling of the galvanic coupling in aluminium alloys by local probe techniques such as the Scanning Vibrating Electrode Technique (SVET) and the microcapillary electrochemical cell (microcell). Polarization curves obtained by the microcell were introduced as input conditions in the model based on Laplace or Nernst–Planck equation. SVET measurements were performed to determine the coupling current distribution on an Al/Al4%Cu bimetallic system. Agreement was found between simulated and experimental current distributions depending on the input conditions and the solve…
Influence of the microstructure and laser shock processing (LSP) on the corrosion behaviour of the AA2050-T8 aluminium alloy
2011
International audience; The corrosion behaviour of AA2050-T8 was studied after polishing and after laser shock processing (LSP) treatment using the electrochemical microcell technique and the SVET. After polishing, pitting at constituent particles and intergranular corrosion were observed. By contrast, no intergranular corrosion developed after LSP. Microcell measurements revealed that LSP increases the pitting potential. SVET measurements revealed that local anodic currents are systematically lower on LSP-treated surfaces than on polished ones. The current density on the LSP-treated surface remains constant around 50 μA cm−2 up to 123 min after immersion, while on the polished surface it r…
Local electrochemical impedance spectroscopy study of the influence of ageing in air and laser shock processing on the micro-electrochemical behaviou…
2011
International audience; In the present paper, the micro-electrochemical behaviour of AA2050-T8 in 0.1 M NaCl was first studied after polishing by means of local electrochemical impedance spectroscopy and field-emission scanning electron microscopy/electron dispersive spectroscopy (FE-SEM/EDS). The influence of ageing in air and LSP was then investigated. Ageing in air for three months led to an increase in the charge transfer resistance. This was clearly observed in sites surrounding constituent particles where the charge transfer resistance was in the order of 1 MΩ cm2 (instead of 10-3 MΩ cm2 after polishing). Increased passivity around particles was confirmed from FE-SEM/EDS analysis. On …
Corrosion resistance of the FeAlC permanent magnet alloy
1998
Abstract The correlation between corrosion behaviour rate of hard magnetic FeAlC alloys and their microstructure and phase composition is presented. Potentiokinetic polarization curves of the tested material in acid (pH = 1 and 2) and neutral (pH = 7) sulphate solutions have been measured. For open-circuit condition, kinetic curves of etching of the samples in 0.5 M H2SO4 have been determined. The resistance of the tested magnets against atmospheric corrosion has been evaluated using a salt-spray test. The atmospheric corrosion rate is 1.5–2 times slower than that found for Nd-Fe-B type magnets. The FeAlC alloys show good corrosion resistance in neutral environments and corrode at rates…
Beta forging of Ti-6Al-4V: Microstructure evolution and mechanical properties
2013
Titanium alloys are finding an increasing use in the aeronautical field, due to their characteristics of high mechanical properties, lightness and corrosion resistance. Moreover these alloys are compatible with the carbon fibre reinforced plastics that are also finding a wide use in the aeronautical field. On the other hand the use of these alloys implies some drawbacks, for example titanium alloys are often considered more difficult to form and generally have less predictable forming characteristics than other metallic alloys such as steel and aluminum. In this paper was studied both the microstructure evolution and the mechanical properties of a Ti-6Al-4V rolled bar after hot forging. The…
Influence of the mode of introduction of a reactive element on the high temperature oxidation behavior of an alumina-forming alloy. Part I: Isotherma…
2004
Several routes of yttrium introduction were applied to test the high temperature oxidation performance of a FeCrAl alloy. Isothermal oxidation tests were described in a previous paper (Part I of this paper in this journal, 2004, 55, 352). Cyclic oxidation tests were performed in air under atmospheric pressure on blank specimens, Y 2 O 3 sol-gel coated-, Y 2 O 3 metal-organic chemical vapor deposited (MOCVD)-, yttrium ion implanted-alloys, as well as on a steel containing 0.1 wt.% of yttrium as an alloying element. For the 20 hours cycles, all the samples, except FeCrAl-0.1Y, exhibit weight losses after a few cycles, indicating drastic spallation of the oxide scales. The MOCVD coated specime…
Reactive Element (Y,Ce) Effect on Stresses Determined In-Situ during Iron Oxidation at 800°C
2001
In-situ stress determinations by X-ray diffraction have been performed during pure iron oxidation (p(O 2 ) = 2 x 10 -3 Pa, T = 800°C). On yttrium implanted specimens the stress level is close to zero before oxidation. On CeO 2 coated specimens, the initial compressive stress due to surface polishing is not modified by the coating. During oxidation, the in-situ compressive stress value determined in the Fe (1-x) O scale, is not strongly dependent upon the reactive element nature. Nevertheless, the stress evolution during cooling and residual stresses determined after cooling to room temperature are very different. Blank and CeO 2 coated specimens show relatively high compressive stresses whe…
Influence of Chlorine, Sulphur and Water Vapor on High Temperature Corrosion of Fe, Cr, Ni Alloys for Waste Incinerators
2006
The behavior of three different materials with respect to their Fe, Cr, Ni contents have been studied between 450°C and 700°C, in waste incinerators combustion conditions, where it occurs a main influence of chlorine, sulfur and water vapor. This works analyzes the behavior of these materials which depends on their capability to form melted compounds and on the nature of these melted phases. Also as the corrosion mechanism is influenced by the presence or missing of any corrosive species, the study focalizes on the specific influence of SO2 and alkaline chorine. Effect of additive ashes on the corrosion behavior of tested materials is also studied. The mechanism of corrosion in waste incine…
A Grain-Scale Model of Inter-Granular Stress Corrosion Cracking in Polycrystals
2017
In this contribution, we propose a cohesive grain-boundary model for hydrogen-assisted inter-granular stress corrosion cracking at the grain-scale in 3D polycrystalline aggregates. The inter-granular strength is degraded by the presence of hydrogen and this is accounted for by employing traction-separation laws directly depending on hydrogen concentration, whose diffusion is represented at this stage through simplified phenomenological relationships. The main feature of the model is that all the relevant mechanical fields are represented in terms of grain-boundary variables only, which couples particularly well with the employment of traction-separation laws.
Mechanical properties and corrosion behaviour of low carbon martensitic stainless steel after machining
2014
The influence of different combinations of cutting conditions on the mechanical behaviour (microhardness), the microstructure and the corrosion behaviour in NaCl solution (using the electrochemical microcell technique and pulse potentiodynamic testing) of a low carbon martensitic stainless steel (grade X4CrNiMo16.5.1 stainless steel) after tempering treatment was studied. Microhardness was increased on the machined surface. In addition, the electrochemical experiments have shown that the machined materials have a heterogeneous electrochemical behaviour. Significant effect of machining on pitting corrosion was noticed. The pitting potential was found to decrease as the microhardness increase…