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1.
The aim of this paper is to study the effect of N+ ion implantation on corrosion and phase formation on the implanted surfaces of Ti-6Al-4V and Ti-6Al-7Nb alloys. Nitrogen ion was implanted on Ti-6Al-4V and Ti-6Al-7Nb alloys at an energy of 70 and 100 keV, respectively using a 150 keV accelerator at different doses ranging from 5 × 1015 to 2.5 × 1017 ions/cm2. Electrochemical studies have been carried out in Ringer’s solution in order to determine the optimum dose that can give good corrosion resistance in a simulated body fluid condition. The implanted surfaces of such modified doses were electrochemically passivated at 1.0 V for an hour. Secondary ion mass spectroscopy was used to study and characterize titanium oxide and titanium nitride layers produced on implanted surface and to correlate them with the corrosion resistance. The nature of the passive film of the implanted-passivated specimen was compared with the unimplanted-passivated as well as as-implanted specimens.  相似文献   

2.
Corrosion of Zircaloy-4 and its welds in nitric acid medium   总被引:1,自引:0,他引:1  
Zirconium and its alloys are considered as candidate materials for various applications in spent nuclear fuel reprocessing plants involving nitric acid of various concentrations at different temperatures. In the present work an attempt was made to study the corrosion behaviour of Zircaloy-4 (Zr-with Sn-1.5%, Fe-0.22%, Cr-0.1%) in wrought and welded forms in comparison with other candidate materials like commercially pure Titanium (CP-Ti), Ti-5%Ta and Ti-5%Ta-2%Nb. Manual TIG welding and electron beam welding was carried out with Zircaloy-4 pipes of 5 mm thick and 120 mm diameter, and radiography was made for choosing defect-free regions for making samples for corrosion investigations. Three phase corrosion testing in liquid, vapour and condensate regions was conducted in boiling 11.5 M nitric acid medium using a specially designed experimental set up. The results indicated that Zircaloy-4 exhibit superior corrosion resistance in both wrought and welded conditions in comparison with other materials. The electron beam welded samples did not show any deterioration and performed similar to wrought alloy. The detailed results of microstructure, microhardness, corrosion rate, morphology of attack and nature of surface film formed are presented in this paper. The results of the present investigation indicated that Zircaloy-4 could be a candidate material for nitric acid medium of high concentration and temperature in reprocessing plants and other industries.  相似文献   

3.
The electrochemical behaviour of Cu-40Zn alloy, in 3% NaCl medium pure and polluted by 2 ppm of S2− ions, has been studied in the absence and presence of the 3-amino-1,2,4 triazole (ATA) as corrosion inhibitor. Electrochemical measurements (polarisation curves and electrochemical impedance spectroscopy) showed that sulphides accelerate the alloy corrosion. The studies revealed that ATA inhibits both cathodic and anodic reactions, indicating a mixed type of inhibition. The inhibiting effect was higher in presence of S2− ions than in its absence. Scanning electron microscopy analysis showed that the inhibitor acts by preventing the adsorption of S2− ions, and formation of Cu2S at the alloy surface. The inhibition efficiency reaches 98% at a concentration of 5 × 10−3 M.  相似文献   

4.
The corrosion characteristics of bare, heat treated and cobalt coated titanium alloys were studied and compared with that of SS 316 in molten carbonates (Li/K = 62/38 vol.%) at 650 °C under oxygen atmosphere using electrochemical and surface characterization techniques. Immersion test of titanium alloys conducted in cathode environment followed by atomic absorption spectroscopy (AAS) indicated leaching of molybdenum from the alloy. Coating the alloy with Co was found to decrease the molybdenum dissolution rate. X-ray diffraction results showed the formation of LiTiO2 and Li2TiO3 on the surface of the titanium alloys and formation of LiFeO2 and Fe2O3 in the case of SS 316. SEM and EDAX analysis of the post-test samples revealed the loss of Mo, Sn and Zr from the titanium alloys and loss of Cr and Ni from SS 316. Electrochemical studies showed that the conductivity of the corrosion scale was higher for cobalt electroplated alloy when compared to other titanium alloys and lower than that of SS 316. Cobalt coated titanium alloy exhibited higher polarization resistance than other alloys. The present study confirmed that the surface modification of titanium alloy lead to the formation of a protective layer with better corrosion barrier properties and better electronic conductivity in molten carbonate fuel cell cathode operating conditions.  相似文献   

5.
A novel protective coating, consisting of three layers (top: diamond-like carbon, middle: aluminum nitride, bottom: aluminum), was deposited on the surface of AZ31 magnesium alloy layer by layer. Nano-indenter, electrochemical system and tribological tester were performed to investigate the hardness, wear resistance and corrosion resistance of the coated AZ31 magnesium alloy, respectively. The DLC/AlN/Al coating improved the magnesium alloy's surface hardness and reduced its friction coefficient, which consequently induced a great improvement of the magnesium alloy's wear resistance. Furthermore, the corrosion resistance of the AZ31 magnesium alloy with the DLC/AlN/Al coating was also enhanced with the corrosion current density decreasing from 2.25 × 10−5 A/cm2 to 1.28 × 10−6 A/cm2 in a 3.5 wt.% NaCl solution.  相似文献   

6.
Isothermal compression testing of Ti-22Al-25Nb alloy was carried out at deformation temperatures between 940 and 1060 °C with strain rate between 0.001 and 10 s−1, and a height reduction of 50%. The hot deformation behavior of Ti-22Al-25Nb alloy was characterized based on an analysis of the stress-strain behavior, kinetics and the processing map, for obtaining optimum processing windows and achieving desired microstructures during hot working. The constitutive equation was established, which described the flow stress as a function of the strain rate and deformation temperature. The apparent activation energies were calculated to be 788.77 kJ/mol in the α2 + β/B2 + O phase region and 436.23 kJ/mol in the α2 + B2 phase region, respectively. Based on Dynamic Material Model and the Murty instability criterion, the processing map for the Ti-22Al-25Nb alloy was constructed for strain of 0.6. The map exhibits a stable domain for the temperature range of 940-1060 °C and strain rate range of 0.001-0.1 s−1 with two peaks in power dissipation of 51 and 56%, occurring at 940 °C/0.001 s−1 and 1060 °C/0.001 s−1, respectively. One is associated with lamellar globularization, and the other displays a phenomenon of recrystallization. Therefore, the desired processing condition of the Ti-22Al-25Nb alloy is 940 °C/0.001 s−1 in the α2 + β/B2 + O phase field. Moreover, the material also undergoes flow instabilities at strain rates higher than 1 s−1. This instability domain exhibits flow localization and adiabatic shear bands which should be avoided during hot processing in order to obtain satisfactory properties.  相似文献   

7.
A systematic study of the isothermal corrosion testing and microscopic examination of Fe3Al alloy in liquid zinc containing small amounts of aluminum (less than 0.2 wt.%) at 450 °C was carried out in this work. The results showed the corrosion of Fe3Al alloy in molten zinc was controlled by the dissolution mechanism. The alloy exhibited a regular corrosion layer, constituted of small metallic particles (diameter: 2-5 μm) separated by channels filled with liquid zinc, which represented a porosity of about 29%. The XRD result of the corrosion layer formed at the interface confirmed the presence of Zn and FeZn6.67. The corrosion rate of Fe3Al alloy in molten zinc was calculated to be approximately 1.5 × 10−7 g cm−2 s−1. Three steps could occur in the whole process: the superficial dissolution of metallic Cr in the corrosion layer, the new phase formation of FeZn6.67 and the diffusion of the dissolved species in the channels of the corrosion layer.  相似文献   

8.
The present paper studies the effect of ion implantation of 2 × 1016 ions/cm2 of Ce+ and 2 × 1016 ions/cm2 of La+ at 150 keV on the corrosion behaviour of hot-dip galvanised steel. After implantation, galvanised steel was characterised by means of XPS previous to and following immersion in the medium. The results revealed incorporation of cerium and lanthanum on the surface as Ce2O3 and La2O3, respectively. Electrochemical impedance spectroscopy was carried out in order to evaluate its corrosion behaviour in 0.6 M NaCl during 1 month of immersion. The corrosion resistance was improved by an increase in the charge transfer resistance of the implanted specimens in the medium. This effect could be associated with changes in the morphology/microstructure of the corrosion products layer rather than in its composition variations.  相似文献   

9.
The hydrogen absorption behaviour during acid etching for the surface modification of commercial pure Ti, Ti-6Al-4V and Ni-Ti superelastic alloys has been investigated on the basis of the surface morphology, electrochemical behaviour and hydrogen thermal desorption analysis. To simulate the conventional acid etching for the improvement of the biocompatibility of Ti alloys, the specimens are immersed in 1 M HCl, 1 M H2SO4 or 0.5 M HCl + 0.5 M H2SO4 aqueous solution at 60 °C. Upon immersion, commercial pure Ti absorbs substantial amounts of hydrogen irrespective of the type of solution. In H2SO4 or HCl + H2SO4 solutions, the hydrogen absorption occurs for a short time (10 min). For Ti-6Al-4V alloy, no hydrogen absorption is observed in HCl solution, whereas hydrogen absorption occurs in other solutions. For Ni-Ti superelastic alloy, the amount of absorbed hydrogen is large, resulting in the pronounced degradation of the mechanical properties of the alloy even for an immersion time of 10 min, irrespective of the type of solution. The hydrogen absorption behaviour is not necessarily consistent with the morphologies of the surface subjected to corrosion and the shift of the corrosion potential. The hydrogen thermal desorption behaviour of commercial pure Ti and Ni-Ti superelastic alloy are sensitively changed by acid etching conditions. The present results suggest that the evaluation of hydrogen absorption is needed for each condition of acid etching, and that the conventional acid etching often leads to hydrogen embrittlement.  相似文献   

10.
TiNi shape memory alloy has been modified by Ta plasma immersion ion implantation technology to improve corrosion resistance. The results of the polarization tests show that the corrosion resistance of TiNi alloy in Ringer's solution at 310 K has been improved by the Ta ion implantation and the Ta/TiNi sample with a moderate incident dose of 1.5 × 1017 ions/cm2 exhibits the best corrosion resistance ability. The surface characterization and chemical composition of the Ta/TiNi samples were determined by Auger electron spectroscopy (AES), Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) methods. AFM images reveal that compact aggregates of nano-grains uniformly disperse on the surface of the Ta/TiNi samples. AES and XPS analyses on the Ta/TiNi sample show that the component of the surface layer is mainly composed of TiO2 and Ta2O5, which is benefit to the corrosion resistance ability and biocompatibility.  相似文献   

11.
Hybrid coatings based on organically modified silicate (Ormosil)-NiZn ferrite/polyaniline (10-30 wt.%) were synthesized through a sol-gel technique. Tetraethylenepentamine, 3-glycidoxypropyltrimethoxysilane, tetraethoxysilane and Ni0.5Zn0.5Fe2O4/polyaniline were used as precursors for the hybrid coatings. These hybrid films were deposited via spin coating onto an aluminum alloy to improve the corrosion protection. The effects induced by the NiZn ferrite/polyaniline content on the chain dynamics, ferromagnetic behavior and corrosion performances of the coated samples were investigated. The rotating-frame spin-lattice relaxation times and scale of the spin-diffusion path length indicated that the configuration of the hybrid films was highly cross-linked, dense and adhered to the aluminum alloy substrates. The magnetic properties of the resulting hybrids showed super-paramagnetic behavior, such as zero coercive force (coercivity = 0 G) and a low blocking temperatures (45 K). Potentio-dynamic and salt-spray analysis revealed that the hybrid films provided an exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates.  相似文献   

12.
A photon rupture method, film removal by a focused pulse of pulsed Nd-YAG laser beam irradiation, has been developed to enable oxide film stripping at extremely high rates without contamination from the film removal tools. In the present study, Zn-55mass%Al alloy and Al-9mass%Si alloy-coated steel specimens covered with protective nitrocellulose film were irradiated with a focused pulse of a pulsed Nd-YAG laser beam at a constant potential in 0.5 kmol m−3 H3BO3-0.05 kmol m−3 Na2B4O7 (pH = 7.4) with 0.01 kmol m−3 of chloride ions to investigate the initial stage of localized corrosion. At low potentials, oxide films on both coated alloys were reformed after the nitrocellulose films were removed by this method. The oxide film formation kinetics follows an inverse logarithmic law, in agreement with Cabrera-Mott theory. However, at high potentials, localized corrosion producing corrosion products occurs at the area where nitrocellulose film was removed. Nevertheless, when the applied potential is less noble, the dissolution current of the Zn-55mass%Al-coated steel samples is higher than that of Al-9mass%Si-coated samples.  相似文献   

13.
The Al ion implantation into AZ31 magnesium alloy was carried out in a MEVVA 80-10 ion implantation system at an ion energy of 40-50 keV with an ion implantation dose ranging from 2 × 1016 to 1 × 1017 ions/cm2 at an elevated temperature of 300 °C induced by an ion current density of 26 μA/cm2. The concentration-depth profile of implanted Al in AZ31 alloy measured by Rutherford backscattering spectrometry (RBS) is a Gaussian-type-like distribution in a depth up to about 1200 nm with the maximum Al concentration of about 8 at.%. The X-ray diffraction (XRD) analysis revealed the formation of α-Mg(Al) phase, intermetallic β-Mg17Al12, and MgO phase on the Al ion implanted samples. The potentiodynamic anodic polarization curves of the Al ion implanted samples in the 0.01 mol/l NaCl solution with a pH value of 12 showed increases of the corrosion potential and the pitting breakdown potential, and a decrease of the passive current density, respectively. The Al ion implanted samples with 6 × 1016 ions/cm2 achieved the high pitting breakdown potential to about − 480 mV (SCE). In the 0.08 mol/l NaCl solution with pH = 12, the Al ion implanted samples with 1 × 1017 ions/cm2 showed an increased pitting breakdown potential to about − 1290 mV (SCE), from around − 1540 mV (SCE) of unimplanted samples. It is indicated that different corrosion mechanisms are responsible for improvement in corrosion resistance of the AZ31 magnesium alloy in the NaCl solutions with the varied concentrations.  相似文献   

14.
Titanium dioxide (TiO2) films have been deposited onto stainless steel substrates using atomic layer deposition (ALD) technique. Composition analysis shows that the films shield the substrates entirely. The TiO2 films are amorphous in structure as characterized by X-ray diffraction. The electrochemical measurements show that the equilibrium corrosion potential positively shifts from − 0.96 eV for bare stainless steel to − 0.63 eV for TiO2 coated stainless steel, and the corrosion current density decreases from 7.0 × 10− 7 A/cm2 to 6.3 × 10− 8 A/cm2. The corrosion resistance obtained by fitting the impedance spectra also reveals that the TiO2 films provide good protection for stainless steel against corrosion in sodium chloride solution. The above results indicate that TiO2 films deposited by ALD are effective in protecting stainless steel from corrosion.  相似文献   

15.
The effects of nitrogen ion implantation on corrosion behaviour of 304L stainless steel in 1 N HNO3 medium were investigated using surface analytical and electrochemical techniques. Nitrogen ion was implanted at 70 keV in the dose range of 1 × 1015, 1 × 1016, 1 × 1017 and 2.5 × 1017 N+/cm2, respectively. Grazing incidence X-ray diffraction results for unimplanted and up to dose of 1 × 1016 N+/cm2 showed co-existence of γ-Fe and α′-Fe and, at higher doses (1 × 1017 and 2.5 × 1017) preferential formation of chromium nitride was observed. X-ray photoelectron spectroscopy investigation confirmed the formation of chromium nitride at higher doses. Electrochemical corrosion investigation revealed nobler open circuit potential, decrease in corrosion current densities, passive current densities and increase in polarization resistance with increase in dose rate. Surface morphology analysis after polarization study using atomic force microscope showed grain boundary dissolution for unimplanted specimens and resistance to surface dissolution with increase in dose rate for implanted specimens.  相似文献   

16.
The corrosion behaviour of Ti-15Mo alloy in 0.15 M NaCl containing 0.01, 0.03, 0.06 and 0.5 M NaF is evaluated and its protective ability is compared with that of CP-Ti and Ti-6Al-4V alloy, to ascertain their suitability for dental implant application. The steady state current density of CP-Ti and, Ti-15Mo and Ti-6Al-4V alloys in 0.15 M NaCl containing 0.03 M NaF at 200 mV vs. SCE is found to be 1, 2 and 6 μA/cm2, respectively, which indicate that all of them could offer a better corrosion resistance in the potential range that could exists in the oral environment.  相似文献   

17.
An attempt was made to understand the effect of silicate based plasma electrolytic oxidation (PEO) coating on the stress corrosion cracking (SCC) behaviour of an AZ61 wrought magnesium alloy. The SCC behaviour of untreated and PEO coated specimens was assessed using slow strain rate tensile tests at two different nominal strain rates, viz. 1 × 10−6 s−1 and 1 × 10−7 s−1, in ASTM D1384 test solution at ambient conditions. The PEO coating was found to improve the general corrosion resistance to a significant extent; however, the improvement in the resistance to stress corrosion cracking was only marginal.  相似文献   

18.
Light-emitting poly(3-methylthiophene) (P3MT) nanowires with a diameter of ∼200 nm were fabricated using an electrochemical polymerization method based on an anodic alumina oxide (Al2O3) nanoporous template. The relatively high energy (3 MeV) Cl2+ ions were irradiated onto the P3MT nanowires with dosages from 1 × 1013 to 1 × 1015 ions/cm2. To study the effect of high energy ion irradiation on P3MT nanowires, we measured UV/vis absorbance, Raman spectra, and laser confocal microscope photoluminescence (PL) on the nanometer scale. The relative atomic concentrations of carbon elements in the pristine and the 3 MeV Cl2+ ion-irradiated P3MT nanowires were investigated through XPS experiments. As the dosage of the 3 MeV Cl2+ ion irradiation increased, we observed that the P3MT nanowires changed to a partially carbonized form, and that the PL efficiency of the systems decreased.  相似文献   

19.
Electrochemical techniques, weight loss method and surface analysis were used to study the synergistic inhibition offered by Zn2+ and piperidin-1-yl-phosphonic acid (PPA) to the corrosion of Armco iron in 3% chloride solution. It is observed that the combination between PPA and Zn2+ shows excellent inhibition efficiency. The potentiodynamic polarization curves reveal that 5 × 10−3 mol l−1 of PPA has only 76.7% inhibition efficiency whereas the mixture containing 5 × 10−3 mol l−1 PPA -20%Zn2+ has 90.2% inhibition efficiency. This suggests that a synergistic effect exists between Zn2+ and PPA. The Fourier transform infrared (FTIR) spectrum of the film formed on iron indicates phosphonates zinc salt formation. A suitable mechanism of corrosion inhibition is proposed based on the results obtained. The surface film analysis showed that in the absence of Zn2+, the protective film consists of Fe2+-PPA complex formed on the anodic sites of the metal surface, whereas in the presence of Zn2+, the protective film consists of Fe2+-PPA complex and Zn(OH)2.  相似文献   

20.
In the present investigation, surface modification of Ti-6Al-7Nb alloy with nitrogen ions is considered as a method to improve its performance with respect to corrosion. Nitrogen ion was implanted on Ti-6Al-7Nb alloy at an energy of 70 and 100 keV using a 150 keV accelerator at different doses between 1×1016 and 3×1017 ions/cm2. Gracing incidence X-ray diffraction was employed on the implanted specimens to understand the phases formed with increasing doses. The implanted samples were subjected to electrochemical study in Ringer's solution in order to determine the optimum dose that can give good corrosion resistance in a simulated body fluid condition. The OCP of the implanted specimens were found to shift in the noble direction in comparison with unimplanted specimen. The passive current density and area of the repassivation loop were found to decrease as the dose values increased. The electrochemical impedance spectroscopic results indicate that the polarization resistance was higher for the dose of 2.5×1017 ions/cm2 implanted at both energy of 70 and 100 keV. Nitrogen ion implantation enhanced the passivability and reduces the corrosion kinetics of the alloy surface with increasing tendency for repassivation. Nature of the surface and reason for the variation and improvement in corrosion resistance are discussed in detail.  相似文献   

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