Comparison of corrosion behavior of zirconium bombarded with self-ion and molybdenum ion

In order to study the effects of zirconium and molybdenum ion bombardment on the aqueous corrosion behavior of zirconium, one group of specimens was implanted with zirconium ions with ions surface densities ranging from 1 × 10¹⁵ to 2 × 10¹⁷ ions/cm² at about 170 °C, using a metal vapor vacuum arc (MEVVA) source operated at an extraction voltage of 50 kV. The other group of specimens was bombarded with molybdenum ion with ions surface densities ranging from 1 × 10¹⁶ to 5 × 10¹⁷ ions/cm² at about 160 °C, using a MEVVA source operated at an extraction voltage of 40 kV. The valence states and depth distribution of elements in the surface of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. Polarization curves measurement was employed to evaluate the aqueous corrosion resistance of the zirconium samples in a 1N H₂SO₄ solution. It was found that the aqueous corrosion resistance of zirconium implanted with 5 × 10¹⁶ Zr ions/cm² is the best in first group samples. For molybdenum ion implantation, the aqueous corrosion resistance of samples declined with raising ions surface densities. The natural corrosion potentials of zirconium samples bombarded with self-ions are more negative than that of the as-received zirconium. While, as for molybdenum ion implantation, the results are opposite. Finally, the mechanisms of the corrosion behavior of the zirconium samples implanted with zirconium and molybdenum ions are discussed.     

Experimental investigation on corrosion and hardness of ion implanted AISI 316L stainless steel

The AISI 316L stainless steel has been widely used both in artificial knee and hip joints in bio-medical applications. In the present study AISI 316L SS was implanted with two different ions: nitrogen and helium at 100 keV with a dose of 1 × 10¹⁷ ions/cm² at room temperature. The crystallographic orientation and surface morphology were studied using X-ray diffraction (XRD) and scanning electron microscope (SEM). The effects of ion implantation on the corrosion performance of AISI 316L stainless steel was evaluated in 0.9% NaCl solution using electro chemical test both on the virgin and implanted samples. The subsequent Tafel analysis shows that the ion implanted specimens were more corrosion resistant when compared to the bare specimens. Microhardness was also measured by Vickers method by varying the loads. The results of the studies indicated that there was a significant improvement in both corrosion resistance and hardness of implanted samples.     

Surface analysis of argon-implanted zircalloy-2 and influence of bubble formation on the corrosion behavior

In order to simulate the irradiation damage, argon ions were implanted into zircalloy-2 alloy with a fluence ranging from 1×10¹⁶ to 1×10¹⁷ ions/cm², using an implanter at an extraction voltage of 190 kV, at liquid nitrogen temperature. Then the effect of argon ion implantation on the aqueous corrosion behavior of zircalloy-2 alloy was studied. The valence states of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) was used to examine the microstructure of the argon-implanted samples. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the argon ion implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zircalloy-2 alloy in a 1 M H₂SO₄ solution. It was found that the bubbles were formed on the surface of implanted samples; the bubbles grew larger with increasing argon fluence. The microstructure of argon-implanted samples changed from amorphous to partial amorphous, then to polycrystalline and finally to amorphous. The bubble forming and changing and microstructure changes affected the corrosion properties of implanted samples. Finally, the mechanism of the corrosion behavior of argon-implanted zircalloy-2 alloy is discussed.     

Effect of Titanium ion implantation on the oxidation behaviour of zircalloy-4 at 500 °C

The beneficial effect of titanium ion implantation on the oxidation behaviour of zircalloy-4 at 500 °C was investigated. Titanium ions were implanted by a MEVVA source at an energy of 40 keV with dose 5×10¹⁶, 1×10¹⁷, and 2×10¹⁷ ion/cm² at the maximum temperature 130 °C. Weight gain curves of the as-received and implanted zircalloy-4 were measured after oxidation in air at 500 °C for 100 min. It was found that improvement was achieved in the oxidation behaviour of titanium ion implanted samples compared with that of the as-received one. The valence of the oxides in the scale was analyzed by X-ray photoemission spectroscopy. Glancing angle X-ray diffraction was used to examine the phase transformation in the oxide films and is showed that the addition of titanium transformed the phase from monoclinic zirconia to hexagonal zirconia. Finally, the mechanism of improvements oxidation behaviour is discussed.     

Role of aluminum ion implantation on microstructure, microhardness and corrosion properties of titanium alloy

Ti-Al-Zr alloy was implanted with Al at cumulative doses between 1 × 10¹⁷ and 1 × 10¹⁸ ions/cm². The results indicate that the Al-implanted layers are ∼0.1 μm thick and are composed almost entirely of an amorphous layer. Implanted layer hardness is dose dependent and is increased by more than a factor of 4 for the high-dose implanted specimen when compared with that of the substrate material. The corrosion resistance of the sample was markedly improved after aluminum implantation.     

Studies on the corrosion behavior of cerium-implanted zircaloy-4 with GAXRD

In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zircaloy-4, specimens were implanted by cerium ions with a fluence range from 1×10¹⁶ to 1×10¹⁷ ions/cm² at maximum 150°C, using MEVVA source at an extracted voltage of 40 kV. The valence and elements penetration distribution of the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the cerium ion implantation in the oxide films. Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zircaloy-4 in a 1 N H₂SO₄ solution. It was found that a significant improvement in the aqueous corrosion behavior of zircaloy-4 implanted with cerium ions compared with that of the as-received zircaloy-4. The improvement effect will declined with raising the implantation fluence. The bigger is the fluence, the less is the improvement. Finally, the mechanism of the corrosion behavior of the cerium-implanted zircaloy-4 is discussed.     

Properties of implanted PET by W ion using MEVVA implantation

Polyethylene terephthalane (PET) has been modified with W ions from a metal vapour arc source (MEVVA). W ions were implanted at 136 keV to doses ranging from 5×10¹⁵ to 2×10¹⁷/cm². The surface of the implanted PET darkened with increasing ion dose, when the metal ion dose is greater than 1×10¹⁷ cm⁻² the colour changed to metallic bright. The surface resistance obviously decreases with increasing dose. The resistivity is stable after long-term storage. TEM photos revealed the presence of W nanometer particles on the surface resulting from the high does implantation. The depth of implanted layer is approximately between 180 and 100 nm for W-implanted PET to doses of 2×10¹⁷/cm² and 5×10¹⁶/cm², respectively. The conductivity and wear resistance have been improved significantly due to W ion implantation. It can be seen that nanometer particles of W precipitation, and carbides have been formed in the implanted layer. The nano-hardness of the implanted PET has been measured by a nano-indenter. The results show that the surface hardness, modulus and wear resistance could be increased.     

Effect of calcium-ion implantation on the corrosion resistance and bioactivity of the Ti6Al4V alloy

The corrosion resistance and bioactivity of Ti6Al4V alloy after calcium-ion implantation were examined. Polished samples were implanted with a dose of 10¹⁷ Na⁺/cm² at a beam energy of 25 keV. The chemical composition of the surface layer formed during the implantation was determined by XPS and SIMS. The bioactivity of the samples was evaluated by soaking them in a simulated body fluid (SBF) at 37 °C for 168 and 720 h. The corrosion resistance in SBF at 37 °C was determined by electrochemical methods after exposure in SBF for various times. The surfaces of the samples before and after examinations were observed by optical microscopy, SEM-EDS and AFM.The results of the corrosion examinations indicated that under stationary conditions and after short-term exposures, the calcium-ion implanted titanium alloy had an increased corrosion resistance, but during the anodic polarization, calcium-implanted samples underwent pitting corrosion. The microscopic observations show that the precipitations of calcium phosphates are present on the surface, but they do not form a continuous layer.     

Improvement of wear and hardness of steel by nitrogen implantation

This paper reports a study of the influence of atomic nitrogen implantation on the improvement of hardness and wear of AISI 8642 steel. The hardness and wear tests were carried out over the dose range 10¹⁷ -7×10¹⁷ ions/cm² and energy 200 keV. Characterization of the surface and depth profiling of the implanted samples was performed using RBS and XRD techniques. Tribological tests for measuring friction and wear were made on a pin-on-disk stand with different loads for implanted and non-implanted samples. Hardness was measured with a Vickers diamond square-faced pyramid indenter. Nitrogen implantation of steel increased the hardness by about 150% in comparison to the non-implanted samples. The influence of a ‘long-range effect’ established beyond the implanted zone during the ion implantation process on the increase of hardness was discussed. No improvement of the friction coefficient was observed in the steel samples due to nitrogen implantation. On the other hand, the wear at a dose 7×10¹⁷ ions/cm² decreased by a factor of about 20 times compared with the non-implanted steel.     

Effect of sodium-ion implantation on the properties of the surface layers formed on CoCrMo alloy (Endocast SL)

This paper is concerned with the surface modification of a cobalt alloy (Endocast) by sodium-ion implantation and with the effect of this modification on its corrosion resistance. The Na ions were implanted at doses of 1×10¹⁷ and 2×10¹⁷ ions/cm² at energy of 25 keV. The chemical composition of the surface layers formed during the implantation was examined by secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS), and their microstructure by transmission electron microscopy (TEM). The corrosion resistance was determined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 °C. Prior to the measurements, the samples were exposed to the test conditions for 13 h to allow the corrosion potential E_corr to stabilize, and for 181, 733 and 2200 h to investigate how the long-time exposures affect the corrosion resistance. The surfaces of the samples were examined by optical microscopy and by SEM-EDS. The TEM results indicate that the surface layers formed during the Na-implantation are amorphous. The results of the electrochemical examinations obtained for the Na-implanted Endocast samples indicate that the corrosion resistance of the alloy is reduced.     

Studies on the corrosion behavior of lanthanum-implanted zircaloy

In order to study the effects of the lanthanum ion implantation on the aqueous corrosion behavior of zircaloy, specimens were implanted with lanthanum ions using a MEVVA source at an energy of 40 keV, with a dose range from 5 × 10¹⁶ to 2 × 10¹⁷ ions/cm² at about 150°C. The surface structure was investigated by X-ray Diffraction (XRD) and the valence of the lanthanum ions in the surface layer was analyzed by X-ray Photoemission Spectroscopy (XPS). Three-sweep potentiodynamic polarization measurement was employed to evaluate the aqueous corrosion behavior of zircaloy in a 0.5 M H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zircaloy compared with that of the as-received zircaloy. The mechanism of the corrosion resistance improvement of the lanthanum-implanted zircaloy is probably due to the addition of the lanthanum oxide dispersoid into the zircaloy matrix.Financed by Institute of Low Energy Nuclear Physics, Radition Beam and Materials Laboratory, Beijing Normal University     

Cyclic oxidation behaviour of cerium implanted AZ31 magnesium alloys

AZ31 samples were implanted with 90 keV cerium ions with a dose of 1 × 10¹⁷ ions/cm². Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and Glancing angle X-ray diffraction (GAXRD) were used in order to investigate the characterization of elements in the implanted surface. The results indicate that after cerium implantation a pre-oxidation layer with double structure was formed. The influence of cerium implantation on the cyclic oxidation behaviour of AZ31 samples was studied at 773 K in air for 96 h, and the morphologies of the oxide scales were examined by scanning electron microscopy (SEM). It was found that the oxidation resistance of the implanted sample has been improved. The mechanisms to explain the experimental results were also proposed.     

Implantation of silicon ions into a surface layer of the Ti6A14V titanium alloy and its effect upon the corrosion resistance and structure of this layer

The effect of silicon ion implantation upon the corrosion resistance and structure of the surface layers formed during the implantation in the Ti6A14V titanium alloy was examined. The silicon doses were 0.5, 1.5, 3.0 and 4.5 × 10¹⁷Si⁺/cm², and the ion beam energy was 100 keV. The corrosion resistance of the samples exposed to a 0.9% NaCl solution at a temperature of 37 °C was measured using electrochemical methods. The structure of the surface layers formed during the implantation was examined by a transmission electron microscope (TEM). The results of the corrosion resistance examinations have shown that the unimplanted and 0.5 × 10¹⁷Si⁺/cm² implanted samples undergo uniform corrosion. At higher silicon doses, the samples show pitting corrosion. The highest corrosion resistance was shown by the alloy implanted with 0.5 × 10¹⁷Si⁺/cm². It has been found that, after a long-term (1200 h) exposure to a 0.9% NaCl solution, the corrosion resistance of the samples is greater than that observed after a short-term exposure. TEM examinations have shown that, beginning from a dose of 1.5 × 10¹⁷Si⁺/cm², the surface of the Ti6A14V alloy samples becomes amorphous. Heating of the 1.5 × 10¹⁷Si⁺/cm² implanted samples at 200 and 500 °C does not change their structure, whereas after heating at 650 °C, the amorphous phase vanishes.     

Studies on the corrosion behavior of yttrium-implanted zircaloy-4

In order to study the effects of yttrium ion implantation on the aqueous corrosion behavior of zircaloy-4, specimens were implanted with yttrium ions using a MEVVA source at an energy of 40 keV, with a dose range from 1 × 10¹⁶ to 1 × 10¹⁷ ions/cm² at about 150°C. Transmission electron microscopy (TEM) was used to obtain the structural character of the yttrium-implanted zircaloy-4. The valence of the yttrium ions in the surface layer was analyzed by X-ray photoemission spectroscopy (XPS). Three-sweep potentiodynamic polarization measurement was employed to evaluate the aqueous corrosion behavior of zircaloy-4 in a 1 N H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zircaloy-4 compared with that of the as-received zircaloy-4. The mechanism of the corrosion resistance improvement of the yttrium-implanted zircaloy-4 is probably due to the addition of the yttrium oxide dispersoid into the zirconium matrix.     

Wear resistance of TiN coatings implanted with Al and N ions

Titanium nitride (TiN) coatings were prepared on HS 6-5-2 high-speed steel cutting inserts and next implanted either with Al ions (fluence 2×10¹⁷ ions/cm²) or with Al and N ions (fluence (1+1)×10¹⁷ ions/cm²) on the rake face. Microhardness and friction coefficient of the implanted surfaces were examined. A noticeable increase of microhardness in Al implanted inserts has been observed.The elemental composition and structural properties of the surface layer were examined by glow discharge optical emission spectroscopy (GDOES) and gliding angle X-ray diffraction (XRD).The tests of turning of 40 H constructional steel with the cutting inserts have shown an improvement in the implanted inserts, especially marked in those implanted with Al+N.     

Effect of nitrogen ion implantation on the sprayed ZnSe thin films

The ZnSe thin films were deposited onto glass substrates by the spray pyrolysis method using mixed aqueous solutions of ZnCl₂ and SeO₂ at the substrate temperature 430 °C. These films were implanted with 130 keV nitrogen ions to various doses from 1 × 10¹⁶ to 1 × 10¹⁷ ions/cm². We have analysed the properties of the nitrogen ion-implanted ZnSe thin films using X-ray diffraction and optical transmittance spectra. The values of optical bandgap have been determined from the absorption spectra. The bandgap of the N⁺ doped films decreased from 2.70 eV for undoped film to 2.60 eV for maximum doping probably due to band-tailing, whereas the absorption coefficient values increased with the increase of the implantation dose.     

Microstructure and electrochemical properties of Zircaloy-4 under Fe ion irradiation

To investigate the microstructure and electrochemical properties of Zircaloy-4 induced by Fe ion irradiation with the energy of 150 keV at liquid nitrogen temperature, transmission electron microscope analysis (TEM) was employed to analyze the surface layer of the samples irradiated at a dose ranging from 1×10¹³ to 1×10¹⁶ ions/cm², and potentiodynamic polarization measurements were used to evaluate the corrosion resistance of Zircaloy-4 in a 1 N H₂SO₄ solution at room temperature. TEM analyses show that Fe ion irradiation lead to a structural change and amorphous phase formation on the surface of the samples. Moreover, it is indicated from the corrosion tests that with an increase of the irradiation dose, the passive current density increases at first and then decreases rapidly, while the natural corrosion potential goes down at first and then up rapidly. The critical point, where the corrosion properties are transformed from a damaging stage to protecting stage, is at the damage level of 3.19 dpa. Finally, the mechanism for the change of corrosion resistance of the Zircaloy-4 samples is discussed.     

Formation of compounds by high-flux nitrogen ion implantation in titanium

Polycrystalline titanium was implanted with nitrogen ions at energies from 30 to 60 keV and with doses from 1 × 10¹⁶ to 1.5 × 10¹⁸ N⁺-ions cm^–2 at room temperature. The implanted titanium layers were investigated by high-voltage electron microscopy and transmission high-energy electron diffraction. The formation of titanium nitride, titanium carbonitride and titanium carbide phases were considered in relation to their dependence on nitrogen ion implantation dose. In the dose range from 1 × 10¹⁶ up to 1.5 × 10¹⁸ N⁺-ions cm^–2 the cubic phase -TiN _x was formed. In the dose range between 1 to 2.5 × 10¹⁷ and 1.5 × 10¹⁸N⁺-ions cm^–2 the tetragonal phase -Ti₂N was found in addition to the -TiN _x phase. The lattice structure of these titanium nitride phases is a function of the nitrogen ion implantation dose. Additionally, the presence of titanium carbonitrido TiC _y O _x and titanium carbide TiC _y phases can be proved. The analysed titanium nitride, titanium carbUnitride and titanium carbide phases are represented in a state diagram as a function of implantation dose.     

HI-ERDA, Micro-Raman and HRXRD studies of buried silicon oxynitride layers synthesized by dual ion implantation

Silicon oxynitride (Si_xO_yN_z) buried insulating layers were synthesized by dual implantation of nitrogen (¹⁴N⁺) and oxygen (¹⁶O⁺) ions sequentially into single crystal silicon in the ratio 1:1 at 150 keV to ion-fluences ranging from 1 × 10¹⁷ to 5 × 10¹⁷ cm⁻². Heavy ion elastic recoil analysis (HI-ERDA) studies of as implanted samples show Gaussian like distributions of nitrogen and oxygen. After annealing at 800 °C, both the nitrogen and oxygen distributions appear as flat plateau like regions near projected range showing the formation of a continuous buried oxynitride layer. Micro-Raman study of as implanted samples shows a broad peak at 480 cm⁻¹ for all fluences. It signifies a complete amorphization of silicon due to high fluence implantation. The annealing at 800 °C results in the reduction of the intensity of the broad peak observed at 480 cm⁻¹ and also gives rise to an additional peak at 517 cm⁻¹. It shows partial recrystallization of damaged silicon due to annealing. The X-ray rocking curves studies from high-resolution X-ray diffraction (HRXRD) of the samples implanted with different fluences have also further confirmed partial recrystallization of damaged silicon on annealing.     

Influence of the ion implantation of nitrogen and boron and TiN coatings on the corrosion of VT-6 titanium alloy

We study the corrosion-electrochemical properties of VT-6 titanium (α + β)-alloy in solutions of hydrochloric and sulfuric acids after high-energy ion implantation with nitrogen (E = 30 keV) for a dose of 2 · 10¹⁷ ion/cm² with subsequent annealing in a vacuum, with boron (E = 100 keV) for a dose of 1 · 10¹⁵ ion/cm², and with nitrogen and boron, as well as in the presence of ion-plasma titanium-nitride coating. It is shown that the modification of the surface increases the corrosion resistance of titanium in highly concentrated solutions of the acids. Note that the corrosion resistance of the titanium-nitride coating whose thickness does not exceed 10μm is somewhat lower than the corrosion resistance of the implanted alloy. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 89–94, May–June, 2008.