Surface modification of Ti-4Al-2V alloy by nitrogen implantation

Ti-4Al-2V is a new type of alpha titanium alloy that suitable for the application in high-temperature and high-pressure water/steam environment. Ti-4Al-2V can be used in marine engineering, nuclear power industry. In this paper the surface characterization of the Ti-4Al-2V implanted with 75 keV nitrogen with fluences of 3 × 10¹⁷ and 8 × 10¹⁷ N⁺/cm² is investigated by glancing-incidence XRD, XPS and microhardness. The results show that new phase TiN are formed after N implantation in the surface region. The nitrogen implantation increases the surface hardness up to 340 and 260% for fluence of 8 × 10¹⁷ and 3 × 10¹⁷ N⁺/cm², respectively. The enhancement of hardness is related to the formation of TiN and irradiation induced hardness.     

RBS,infrared and diffraction compared analysis of SiC synthesis in C implanted silicon

Monocrystalline (111) and (100) silicon substrates were implanted with singly charged carbon ions, and synthesis of silicon carbide through thermal processes was considered. Implantation energies from 10 to 40 keV were used with fluences ranging between 5×10¹⁶ and 5×10¹⁷ ions cm^?2. Analysis of the material obtained was performed using Rutherford backscattering, infrared spectra and electron diffraction. Correlations between corresponding data reported here give evidence of the respective influence of implantation energy, fluence, substrate orientation and annealing temperature.     

A modified blister test to study the adhesion of thin coatings based on local helium ion implantation

A modified blister test has been developed based on helium ion implantation into selected areas of the metal substrate prior to the coating deposition. After a post-deposition thermal annealing, blisters are formed by agglomeration of the implanted gas at the ceramic–metal interface. This method can be used to control the pressure in the blister which eventually may lead to delamination at the periphery of the blister. A microsieve with a regular array of circular holes is used during the implantation to assure the initial blister size. Two different microsieves were employed in this work, with pore diameters of 1.5 and 4.5 μm, respectively. The distance between the centres of neighbour pores is twice the pore diameter. Scanning Electron Microscopy (SEM) and Confocal Scanning Optical Microscopy (CSOM) observations allowed the determination of the blistering parameters such as the radius, the height and the blister volume. From the gas content and these parameters, the work of adhesion or energy release rate can be obtained.In this work, we present the first results of this blister test applied to W–C:H films and multilayers of Ti and Al deposited by Physical Vapour Deposition on polycrystalline copper substrates. The copper substrates were implanted with 34 keV He⁺ ions up to fluences of 3 and 5×10¹⁶ cm⁻² before the deposition of the coatings and annealed afterwards in vacuum at temperatures from 773 to 1073 K for 30 min. Delamination of the Ti/Al multilayer coatings was already detected after annealing at 873 K with an energy release rate estimated to be 0.5 J m⁻² at a typical helium pressure of 10⁷ Pa. No delamination but only helium swelling was observed for W–C:H coatings annealed at 1073 K. Results of experiments on uncoated copper samples are also shown in order to explain the mechanism of helium bubble growth and helium release that causes the creation of the blisters.     

Effects of the experimental conditions of chemical vapour deposition on a TiC/TiN double-layer coating

Deposits of titanium nitride (TiN) were formed on TiC-coated 94wt.%WC-6wt.%Co substrates by chemical vapour deposition using a TiCl₄, H₂ and N₂ gas mixture. The effects of the deposition temperature, the total flow rate of the reactant gases and the partial pressure of TiCl₄ on the deposition rate, the preferred orientation and the surface morphology of the TiN deposit were investigated. The controlling mechanism of the TiN deposition reaction and its relationship with the deposition temperature and the total flow rate of the reactant gases were also investigated.The deposition rate and the TiN crystal growth along the (220) preferred orientation are increased with an increase in the deposition temperature and an increase in the partial pressure of TiCl₄ at a total flow rate of less than 700 cm³ min^-1. The particle size of the TiN deposit is reduced with an increase in the partial pressure of TiCl₄ and is increased with an increase in the deposition temperature at a total flow rate of less than 700 cm³ min^-1. When the total flow rate is greater than 700 cm³ min^-1, the deposition rate, the TiN crystal growth along the (220) preferred orientation and the particle size of the TiN deposit no longer vary.When the deposition temperature is lower than 1000 °C, the TiN deposition reaction is controlled by the surface reaction; at a temperature above 1000 °C, the reaction is controlled by mass transport. When the total flow rate is less than 700 cm³ min^-1, the deposition reaction is controlled by mass transport; with a total flow rate greater than 700 cm³ min^-1, the reaction is controlled by the surface reaction.     

Effects of nitrogen ion implantation and implantation energy on surface properties and adhesion strength of TiN films deposited on aluminum by magnetron sputtering

The performance of tribological coatings depends greatly on the adhesion strength between the coatings and substrates. In this work, we investigated the influence of the ion implantation energy of nitrogen on the adhesion and surface properties of TiN deposited on aluminum substrate. Aluminum samples were implanted with 15 keV, 30 keV and 40 keV nitrogen ions before TiN films were deposited using magnetron sputtering in a custom-designed multi-functional ion implanter. The adhesion properties of the implanted TiN films were assessed using nano-scratch tests and were observed to vary with the nitrogen ion implantation energy. Our frictional test results show that an appropriate ion implantation energy and dose can improve the frictional behavior of TiN films deposited on aluminum.     

Structural characterization of TiN coatings on Si substrates irradiated with Ar ions

The present study deals with TiN/Si bilayers irradiated at room temperature (RT) with 120 keV Ar ions. The TiN layers were deposited by d.c. reactive sputtering on Si(100) wafers to a thickness of ～ 240 nm. After deposition the TiN/Si bilayers were irradiated to the fluences of 1 × 10¹⁵ ions/cm² and 1 × 10¹⁶ ions/cm². Structural characterization was performed with Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM), grazing angle X-ray diffraction (XRD) and atomic force microscopy (AFM). The results showed that the variation of the lattice constants, mean grain size and micro-strain can be attributed to the formation of the high density damage region in the TiN film structure. It has been found that this damage region is mainly distributed within ～ 100 nm at surface of the TiN layers.     

Nano-scratch study of pulsed laser-deposited hydroxyapatite thin films implanted at high energy with N+ and AR+ ions

In this study we report a method to improve the adherence of hydroxyapatite (HA) thin films, using an ion beam implantation treatment. Crystalline HA films were grown by a pulsed laser deposition technique (PLD), using an excimer KrF* laser. The films were deposited at room temperature in vacuum on Ti-5Al-2.5Fe alloy substrates previously coated with a ceramic TiN buffer layer and then annealed in ambient air at (500–600)°C. After deposition the films were implanted with N⁺ and Ar⁺ ions accelerated at high energy (1–1.5 MeV range) at a fixed dose of 10¹⁶ cm^–2. The intrinsic mechanical resistance and adherence to the TiN buffer layer of the implanted HA films have been evaluated by nano-scratch tests. We used for measurements a spherical indenter with a tip radius of 5 m. Different scratch tests have been performed on implanted and unimplanted areas of films to demonstrate the effects of N⁺ and Ar⁺ ion implantation process on the films properties. Results show an enhancement of the dynamic mechanical properties in the implanted zones and influence of the nature of the implanted species. The best results are obtained for films implanted with nitrogen. The modes of failure of the films under loading are described.     

Surface modification of 316L stainless steel with magnetron sputtered TiN/VN nanoscale multilayers for bio implant applications

Nanoscale multilayered TiN/VN coatings were developed by reactive dc magnetron sputtering on 316L stainless steel substrates. The coatings showed a polycrystalline cubic structure with (111) preferential growth. XPS analysis indicated the presence of peaks corresponding to Ti2p, V2p, N1s, O1s, and C1s. Raman spectra exhibited the characteristic peaks in the acoustic range of 160–320 cm⁻¹ and in the optic range between 480 and 695 cm⁻¹. Columnar structure of the coatings was observed from TEM analysis. The number of adherent platelets on the surface of the TiN/VN multilayer, VN, TiN single layer coating exhibit fewer aggregation and pseudopodium than on substrates. The wear resistance of the multilayer coatings increases obviously as a result of their high hardness. Tafel plots in simulated bodily fluid showed lower corrosion rate for the TiN/VN nanoscale multilayer coatings compared to single layer and bare 316L SS substrate.     

工艺参数对EB-PVD制备YSZ涂层的影响

为探讨电子束物理气相沉积(EB-PVD)制备8 mol.%氧化钇稳定氧化锆(8YSZ)涂层过程中工艺参数对涂层致密性、表面粗糙度和晶粒择优取向生长的影响,利用扫描电镜、原子力显微镜和X射线衍射技术对涂层的上述性能进行了分析.分析结果表明,随沉积速率由750 nm/min下降至20 nm/min,YSZ涂层的晶粒逐渐聚合长大,晶粒之间的孔隙减少,涂层的气体扩散系数相应地由2.41×10-4cm4/(N·s)下降至6.56×10-5cm4/(N·s).YSZ涂层的表面粗糙度随靶基距的提高逐渐降低,涂层的晶体学取向随蒸汽粒子入射角的改变而改变,入射角为30°时(111)晶面具有平行于涂层表面排列的趋势,入射角为45°时(311)和(420)晶面具有平行于表面排列的趋势,而入射角为60°时(220)和(331)晶面具有平行于表面排列的趋势.     

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.     

Surface hardening in N<Superscript>+</Superscript> implanted polycarbonate

The influence of low energy nitrogen ions on the surface hardness of polycarbonate has been studied by implanting some of these specimens with 100 keV N⁺ ions at a beam current of 1 μA/cm² in the dose range of 1 × 10¹⁵ to 1 × 10¹⁷ ions cm^?2. Knoop microhardness has been found to be increased nearly 24 times at a load of 9.8 mN, for the dose of 1 × 10¹⁷ ions cm^?2. The structural changes occurred in implanted specimens were studied by Raman analysis, UV–Visible spectroscopy, and X-ray diffraction techniques. Raman studies point toward the formation of a structure resembling hydrogenated amorphous carbon. Disordering in the surface structure (I _D/I _G ratio) has also been found to increase with ion fluence using Raman technique. UV–Visible spectroscopic analysis shows a clear enhancement in Urbach energy (disorder parameter) from a value of 0.61 eV (virgin sample) to 1.72 eV (at a fluence of 1 × 10¹⁷ N⁺ cm^?2) with increasing ion dose. The increase in Urbach energy has been found to be correlated linearly with the increase in Knoop microhardness number. Results of X-ray diffraction analysis also indicate disordering in implanted layers as a result of implantation. In the present work, the possible mechanism behind the formation of harder surfaces due to implantation has been discussed in detail.     

Effect of ion bombardment on thin hafnium nitride films

The use of ion bombardment in the modification of the surface mechanical properties of hafnium nitride has been investigated. Initially the deposition rate and the composition of the films prepared under different conditions of bias potential, partial pressure of N₂ and substrate temperature during r.f. sputtering were analyzed by Rutherford backscattering spectrometry and ¹⁴N(d, ∝)¹²C nuclear reaction. The concentration of hafnium in the film was dependent on both the substrate temperature and the partial pressure of N₂ during sputtering. Films bombarded with 500 keV Kr⁺ ions at different doses (10¹⁵-10¹⁷ ions cm^-2) indicate only moderate changes in the microhardness compared with similar studies of TiN films. However, the HfN films showed a greater improvement in adhesion compared with TiN films at lower ion doses. Ion channeling studies on single-crystal stainless steel substrates did not show any evidence of ion-induced mixing or recoil implantation of hafnium into the substrate. Preliminary measurements of the sputtering yield at high energies indicate that the modifications in microhardness and adhesion of the films may be explained by possible recoil implantation of some nitrogen into the substrate.     

Influence of deposition temperature on the superconductivity of Y1−x HoxBa2Cu3O7 −δfilms produced by dc-magnetron sputtering

Experimental results of research on the influence of deposition temperature (T _s) on crystal structure and superconductivity of Y_1?x HoxBa₂Cu₃O_{7 ?δ} (YHBCO) films deposited by dcmagnetron sputtering are reported. X-ray diffraction analysis showed that the films grew with preferential orientation of thec-axis normal to the substrate surface in the range of temperature 750–820°C. The single-crystal structure of the YHBCO films grown epitaxially at the optimal substrate temperatures of 820, 800, 760, and 750°C, respectively, have been established by rocking curves, Φ-scan, and electron channeling pattern (ECP). Typical values of the critical current density (A · cm^?2) at 77 K and 0.1 T field are 2.1×10⁵, 4×10⁵, 6.2×10⁵, and 3.1×10⁵ for thex=0, 0.2, 0.4, 0.7 films respectively, measured by a Quantum Design magnetrometer (H∥c).     

Effect of silicon ion implantation on the properties of a cast Co–Cr–Mo alloy

The effect of silicon ion implantation upon the corrosion resistance and structure of the cast Co–Cr–Mo alloy of the Vitalium type, was examined. The silicon fluences were 1.5, 3.0 and 4.5 × 10¹⁷Si⁺ cm^-2. The surface layer of the Vitalium samples implanted with these silicon doses was found to become amorphous. Further annealing of the samples at 200 °C resulted in the Cr₃Co₅Si₂ phase being formed, whereas the amorphous layer was preserved. The Vitalium samples submerged in the 0.9% NaCl solution underwent mainly uniform corrosion, irrespective of whether or not they had been implanted with Si⁺ ions. With increasing doses of implanted silicon and after annealing at 200 °C (samples implanted with 1.5 × 10¹⁷Si⁺ cm^-2), the corrosion resistance increased. The thickness of the oxide layer formed during the anodic polarization depended on the implanted silicon doses. This revised version was published online in November 2006 with corrections to the Cover Date.     

Electrodeposition of dicalcium phosphate dihydrate coatings on stainless steel substrates

Cathodic reduction of an aqueous solution containing dissolved calcium and phosphate ions results in the deposition of micrometer thick CaHPO₄·2H₂O (dicalcium phosphate dihydrate) coatings on stainless steel substrates. The coating obtained at a low deposition current (8 mA cm^???2) comprises lath-like crystallites oriented along 020. The 020 crystal planes are non-polar and have a low surface energy. At a high deposition current (12 mA cm^???2), platelets oriented along 121? are deposited. CaHPO₄·2H₂O is an important precursor to the nucleation of hydroxyapatite, the inorganic component of bones. Differently oriented CaHPO₄·2H₂O coatings transform to hydroxyapatite with different kinetics, the transformation being more facile when the coating is oriented along 121?. These observations have implications for the development of electrodeposited biocompatible coatings for metal endoprostheses for medical applications.     

Effect of Rough-Surfaced Diamond Content on the Microstructure,Tribological Behavior,and Corrosion Resistance of Ni/Diamond Composite Coatings

This study fabricates certain Ni/diamond composite coatings using a coelectrodeposition method and then evaluates the effect of diamond content on the morphology, phase structure, microhardness, wear, and corrosion resistance of such coatings, while exploring their tribological and anticorrosion mechanisms. It is demonstrated that the addition of diamond can change the preferred orientation of Ni from (200) to (111), and its texture coefficient value can be boosted from 23.3% to 64.4% with the increase of diamond content. In the experiment, at a diamond content of 3 g L⁻¹, the deposited diamond particles are more and evenly dispersed across the composite, with the microhardness of nickel-based coatings reaching an optimum value of 613 HV. In addition, the coefficient of friction is reduced to a minimum value of 0.627, while the wear rate is kept at only 1.79 × 10⁻⁵ mm³ Nm⁻¹, indicating a high wear resistance. Electrochemical test results demonstrate that the Ni/diamond composite coatings produced at 3 g L⁻¹ create the maximum charge transfer resistance (5429.3 Ω cm²) and the minimum corrosion current density (2.19 μA cm⁻²), features that can deliver the best corrosion resistance.     

Nitrogen ion implantation for improvement of the mechanical surface properties of aluminum

The results of the surface treatment of commercial aluminum by nitrogen ion implantation at 120 keV and implanted fluences ranging from 3×l0¹⁷ to 1.1×10¹⁸ ions/cm² are reported. The treatment was found to lead to the formation of the hexagonal phase AIN, a decrease in strain and an increase of crystallite sizes. The modification of the surface layer so produced was thought to be a cause of a measured increase in surface microhardness and corresponding decrease in friction coefficient and wear measured in pure methanol. Oxygen found in the surface layers was also thought to play a significant role in determining tribological performance.     

Defect formation in silicon implanted with ∼1 MeV/nucleon ions

Defect formation processes in silicon implanted with ∼1 MeV/nucleon boron, oxygen, and argon ions have been studied using microhardness and Hall effect measurements. The results indicate that ion implantation increases the surface strength of silicon single crystals owing to the formation of electrically inactive interstitials through the diffusion of self-interstitials from the implantation-damaged layer to the silicon surface. The radiation-induced surface hardening depends significantly on the nature of the ion, its energy, and the implant dose. In the case of low-Z (boron) ion implantation, the effect had a maximum at an implant dose of ∼5 × 10¹⁴ cm⁻², whereas that for O⁺ and Ar⁺ ions showed no saturation even at the highest dose reached, 1 × 10¹⁶ cm⁻². When the ion energy was increased to ∼3 MeV/nucleon (210-MeV Kr⁺ ion implantation), we observed an opposite effect, surface strength loss, due to the predominant generation of vacancy-type defects.     

Surface composition and near-surface hardness studies on high dose boron-implanted 304 stainless steel

The modification of boron-implanted near surface of 304 stainless steel having strained and strain-free surfaces was studied. The energy of the boron ion was 130 keV at a dose of 2·5×10¹⁷ ions cm⁻². Ion-implantation is known to modify the tribological properties of metals, however, it is not well-understood as to how such a shallow implanted layer can affect the microhardening. A full understanding of the process involved is yet to emerge. In the present work the ion implanted layer was characterized for boron depth profiles using AES and XPS. The implanted layer is observed to contain B₂O₃, Fe₂B, FeB and CrB₂ compounds with small fractions of chromium and iron oxides. The strain-free surface of 304 SS shows an increase in microhardness by ∼ 80% after boron ion implantation at 2 gf and the strained surface by ∼ 30% at the same load. The annealing effects on microhardness for mechanically polished and implanted samples were also investigated in the temperature range 100 to 400°C. The possible correlation of near-surface microhardness increase with boride formation is discussed.     

Determination of mechanical properties of pulsed laser-deposited hydroxyapatite thin film implanted at high energy with N+ and Ar+ ions, using nanoindentation

Hydroxyapatite (HA) is extensively studied for various applications in bone implantology. We report here a comparison between the effects of ion beam implantation treatment using nitrogen and argon ions, on the mechanical characteristics of HA films grown by pulsed laser deposition. We used for deposition a KrF* excimer laser. Crystalline and stoichiometric HA films were grown on Ti-5Al-2.5Fe alloy substrate, previously coated with a TiN buffer layer. After deposition, the film were implanted with ions of N⁺ and Ar⁺ of high energy (1–1.5 MeV range) and dose set at 10¹⁶ at cm^–2. The hardness and elastic modulus were determined by nanoindentation tests using a spherical tipped nanoindenter with a 5 m-tip radius. From the load-displacement curves, we put into evidence an enhancement of the mechanical characteristics of the HA films after implantation, especially for those implanted with N⁺ ions. This improvement of the mechanical characteristics is related to the changes of surface morphology and the densification of the HA layer after ion treatment.