Applications of combined ion implantation for improved tribological performance

Ion implantation set-up on the base of ion gun with target sputtering by Penning discharge plasma was created. The set-up allows to conduct implantation of ions of various materials with an implantation current of 100 μA/cm² at acceleration voltage of up to 30 kV. Combined implantation of TiB₂ compound and Argon or Nitrogen were applied for surface properties modification of WC-Co hard alloy and SKD11 steel. The effect of implantation on mechanical and tribological properties has been studied and discussed with respect to implantation fluence. It was shown that the main effect of implantation is the modification of thin surface layer with formation of Ti, B, N₂ — base compounds, which leads to modification of surface adhesion interaction and wear resistance improvement. Examples of application to real products are presented.     

Effect of nitrogen ion irradiation on the nano-tribological and surface mechanical properties of ultra-high molecular weight polyethylene

Generation of wear debris is the principal obstacle limiting the durability of ultra-high molecular weight polyethylene (UHMWPE) in biomedical applications. Aiming to enhance UHMWPE wear resistance, surface modification with swift heavy ion irradiation (SHI) appears as a potential and attractive methodology. Contrary to ion implantation techniques, the swift heavy ions range can reach tens to hundreds microns and its extremely high linear energy is able to induce effective chemical modifications using low fluence values. Nano-wear performance and surface mechanical properties of samples of pristine and SHI irradiated (using N₂⁺ ions at 33 MeV and a fluence of 1 × 10¹² ions/cm²) were characterized by depth sensing indentation (DSI) and scanning probe microscopy (SPM). It turned out that modifications induced by irradiation at the surface layers were successful to reduce nano-wear volume and creep deformation. These improvements were related to beneficial changes in hardness, elastic modulus, hardness to elastic modulus ratio and friction coefficient.     

The aqueous corrosion behaviour of an ion implanted 12% chromium steel

Ion implantation has shown beneficial effects in the field of wear and oxidation. This paper is a study of the influence of ion implantation on the corrosion performance of a 12% chromium ferritic steel, 3CR12. 80 keV ions were implanted at concentrations of 5 × 10¹² to 1 × 10¹⁷ ions cm^?2. The effect of implantation of 4 ion types (Mo, V, Ph, N) each at 4 dosages was studied potentiostatically in 1 N H₂SO₄ and 0.1 N NaCl solutions. Uniform corrosion loss calculations would imply that the effect of implantation is not long lasting in 1 N H₂SO₄. This could imply that changes in the potentiostatic curves are brought about by ions in solution. Pb-Implanted 3CR12 showed increased pitting resistance with increasing dosage, whereas Pb-implanted 3CR12 showed poorer pitting resistance. Mo and V implantation showed similar behaviour for the lower doses in that both species enhanced pitting resistance but the results showed poorer pitting resistance for the higher doses. The most important limitation of ion implantation is the shallow depth of penetration and whether or not implantation effects last over sufficent periods of time for practical application is still in question.     

Microstructure and corrosion resistance of tantalum after nitrogen ion implantation

This paper investigates the effect of nitrogen ion implantation on surface structure as well as resistance against tantalum corrosion. Bulk Ta surface was implanted with 30?keV nitrogen ions at a temperature of 100°C with doses between 1?×?10¹⁷ and 1?×?10¹⁸?ions/cm². The implanted samples were characterised by atomic force microscopy, X-ray diffraction analyses and the corrosion test to identify structural, compositional and electrochemical changes at various doses. The experimental results indicate the formation of hexagonal tantalum nitride (TaN_0.43), in addition to the fact that by increasing the ion dose, nitrogen atoms occupy more interstitial spaces in the target crystal, a case which can significantly improve corrosion resistance. The maximum extent in the improvement of the micro hardness was 75% and the reduction in the corrosion current was 83%. According to scanning electronic microscopy and corrosion results, in the dose of 1?×?10¹⁸?ions/cm² the highest corrosion resistance was received against the H₂SO₄ corroding media.     

Nitrogen-PBII modification of ultra-high molecular weight polyethylene: Composition, structure and nanomechanical properties

Plasma based ion implantation of nitrogen was performed on mechanically polished UHMWPE model samples by applying 27.13 MHz RF energized low pressure N₂ plasma with 15-30 kV pulses and fluences up to 5 · 10¹⁷ ions/cm². Surface compositional and structural alterations and nanomechanical property changes were investigated by XPS, Raman and by nano-indentation and nano-scratch techniques. The implanted N amounted up to 13-20 at.% (N/C = 0.18-0.30), while a significant amount of oxygen could also be detected on the surface. Three types of chemical states of the incorporated nitrogen were detected, related to linear sp² CN-C and to planar and non-planar sp³ type C-N bonds. The applied PBII treatment led to severe dehydrogenation of the polyethylene resulting in conversion of the surface into a nitrogen-containing DLC type structure. Up to four-fold increase of the hardness at 50-100 nm depth was measured compared to the untreated samples. The scratch volume, characterising the wear resistance, decreased also significantly down to 25-35% of the original value.     

Effect of nitrogen ion implantation on the localized corrosion behavior of titanium modified type 316L stainless steel in simulated body fluid

Nitrogen ion implantation on titanium-modified type 316L stainless steel (SS) at the energy of 70 keV was carried out at different doses ranging from 1×10¹⁵ to 2.5×10¹⁷ ions/cm². These samples were subjected to open circuit potential (OCP)—time measurement, cyclic polarization, and accelerated leaching studies—in order to discover the optimum dose that can provide good localized corrosion resistance in a simulated body fluid condition. The results showed that the localized corrosion resistance improved with an increase in doses up to 1×10¹⁷ ions/cm², beyond which it started to deteriorate. The results of the accelerated leaching studies showed that the leaching of the major alloying elements was arrested upon nitrogen ion implantation. Gracing incidence x-ray diffraction studies showed the formation of chromium nitrides at a dose of 2.5×10¹⁷ ions/cm². X-ray photoelectron spectroscopy studies revealed the presence of these chromium nitrides in the passive film, which was attributed to the decreased corrosion resistance at a higher dose. Secondary ion mass spectroscopy studies on the passive film showed the variation in the depth profile upon nitrogen ion implantation. Thus, nitrogen ion implantation can be effectively used as a method to improve the corrosion resistance of the orthopedic implant devices made of titanium-modified type 316L SS. The nature of the passive film and its influence on corrosion resistance are discussed in this article.     

Low-energy ion beam treatment of α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>(0001) and improvement of photoluminescence of ZnO thin films

A low energy N₂ ^? ion beam impinged on a α-Al₂O₃(0001) single crystal surface in the range of fluence 5×10¹⁵/cm²?1×10¹⁸/cm² at room temperature. After ion bombardment, chemical bonding on the modified sapphire surface was investigated by x-ray photoelectron spectroscopy. Below a fluence of 1×10¹⁵/cm², only a non-bonded N1s peak at the binding energy 398.7 eV was found, but further irradiation up to 2×10¹⁷/cm² induced Al?O?N bonding at around 403 eV. The occurrence of Al?N bonding was identified at ion fluence higher than 5×10¹⁷/cm² at 396.6 eV. II–VI ZnO thin films were grown on an untreated/ion-beam-induced sapphire surface by pulsed laser deposition (PLD) for the investigation of the modified-substrate effect on photoluminescence. The ZnO films grown on modified sapphire containing Al?O?N bonding only, and both Al?O?N and Al?N bonding showed a significant reduction of the peak related to deep-level defects in photoluminescence. These results are explained in terms of the formation of Al?N?O and Al?O?N layers and relaxation of the interfacial strain between Al₂O₃ and ZnO.     

Nano-wear, nano-hardness and corrosion-resistance of electroplated nickel surfaces after co-implantation of Cr and N2 ions

In this work, a successful sequential co-implantation treatment of Cr⁺ and N₂⁺ ions into electrodeposited nickel plates is presented. The goal of this treatment is the simultaneous enhancement of the wear resistance, mechanical stability and corrosion-protection properties of the Ni surfaces. The ion-implanted surfaces have been characterized by glow-discharge optical-emission spectroscopy, X-ray diffraction, nano-hardness, roughness, nano-wear and potentio-dynamic corrosion tests. It has been observed that the implantation of Cr⁺ or N₂⁺ alone is not sufficient to achieve simultaneously the enhancement of both the wear-resistance and the corrosion-protection properties. Conversely, the sequential implantation of Cr⁺ and N₂⁺ at 140 keV and fluencies of 3 × 10¹⁷ and 1.5 × 10¹⁷ ions/cm² respectively, permits the formation of a functional surface capable of reducing both the corrosion rate and the wear rates, with respect to those exhibited by the un-implanted Ni surfaces.This treatment can be used to protect the surfaces of micro-embossing/stamping dies based on electroformed Nickel, as an alternative to other coating strategies. Furthermore, the ion implantation assures the non-modification of the net-shape and surface finish of these types of dies, which is of crucial importance when they are used for high-precision micro-texturing/imprinting applications.     

Composition and structure of Al ions implanted Fe at elevated temperatures

Al ions with ion energy of 120 keV are implanted into Fe under ion current density of 3.18 μA/cm² to implantation doses of 5 × 10¹⁶ and 1 × 10¹⁷ ions/cm² at room temperature and elevated temperatures of 250 and 500 °C, respectively. At 250 °C, the distribution depth of implanted Al reaches 160 nm with a peak concentration of 6 at.% at the dose of 5 × 10¹⁶ ions/cm², and 180 nm with 10 at.% at 1 × 10¹⁷ ions/cm², analyzed by Rutherford backscattering spectroscopy, respectively. At 500 °C, the implantation depth is 200 nm and the maximum concentration of Al is 10 at.% at the dose of 1 × 10¹⁷ ions/cm². With 5 × 10¹⁶ ions/cm², the intermetallics Al₁₃Fe₄ is formed in the Fe samples at 500 °C, revealed by X-ray diffraction. With 1 × 10¹⁷ ions/cm², the phase is also detected at 250 °C. The concentration-depth profiles of implanted Al in Fe samples at the room temperature, 250 °C and 500 °C are calculated by a mass transfer model that is built based on the transport of ions in matter and the irradiation enhanced diffusion. The calculated concentration-depth profiles are in reasonable agreement with those obtained from the experiments.     

Development and irradiation performance of stencil masks for heavy-ion patterned implantation

Heavy-ion implantation is a powerful tool to conduct atomic injection and to create buried nanoparticles with good depth-controllability in dielectric material. Metal nanoparticle composites, especially, the metal ion implanted insulators (e.g. SiO₂) with patterned nanoparticles are promising for plasmonic applications, possessing an enhanced surface plasmon resonance and nonlinear optical property as compared with randomly implanted specimens [1]. Contact masked implantation is one practical method for patterned implantation, which has advantage of reliable 2D nanoparticle spatial controllability without any abreactions. In this experiment, the Si stencil mask was made from top Si layer of SOI wafer by using e-beam lithography and plasma deep etching. The mask can be fabricated with required aspect ratio (from 3 up to 100), fine pore shape, surface flatness, and mechanical hardness. 60 keV Cu ion irradiation damage test shows that, below the fluence of 1 × 10¹⁷ ions/cm², Si stencil mask can keep dimensional stability.     

Corrosion behaviour of nitrogen implanted titanium in simulated body fluid

Abstract

Titanium is one of the most important materials for medical applications, as a result of its uniquely high biocompatibility. The effect of nitrogen implantation on the biocompatibility and the corrosion resistance of cp titanium are reported. Grazing incidence X-ray diffraction studies showed that implantation formed a δ-TiN_x phase. Electrochemical tests in HBSS showed an optimal decrease in corrosion current density for specimens implanted with 3 × 10¹⁷ ions cm^-2 at 25 keV, compared with unimplanted titanium. Following implantation and immersion in a commercial physiological solution, phases are precipitated which are rich in calcium and phosphorus, and these hydroxyapatite precursors indicate that this implantation regime confers optimal properties of corrosion resistance and biocompatibility.     

Ion implantation of superhard ceramic cutting tools

Despite numerous reports of tool life increase by ion implantation in machining operations, ion implantation applications of cutting tools remain limited, especially for ceramic tools. Mechanisms of tool-life improvement by implantation are not clearly established due to complexity of both implantation and tool-wear processes. In an attempt to improve performance of cubic boron nitride (CBN) tools for hard machining by ion implantation, a literature survey of ion-implanted cutting tools was carried out with a focus on mechanisms of tool-wear reduction by ion implantation. Implantation and machining experiments were then conducted to investigate implantation effects on CBN tools in hard machining. A batch of CBN tools was implanted with nitrogen ions at 150 keV and 2.5×10¹⁷ ions/cm² and further used to cut 61 HRc AISI 52100 steel at different conditions. Results show that ion implantation has strong effects on partsurface finish, moderate effect on cutting forces, but an insignificant impact on tool wear. Friction coefficients, estimated from measured cutting forces, are possibly reduced by ion implantation, which may improve surface finish. However, surprisingly, 2-D orthogonal cutting to evaluate tribological loading in hard machining showed no difference on contact stresses and friction coefficients between implanted and nonimplanted CBN tools. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana.     

Ag和Ta离子双注入改善Ti6Al4V合金耐磨性能

采用Ag和Ta离子双注入对医用Ti6Al4V合金进行表面改性, 即以Ag离子1.0×10¹⁷ cm^-2 先注入、以Ta离子1.5×10¹⁷ cm^-2 后注入合金样品表面. 采用纳米力学探针研究离子注入前、后Ti6Al4V样品表面硬度随压入深度的变化, 利用多功能摩擦磨损试验机分析离子注入前、后样品的耐磨性, 利用XRD和XPS研究样品表面的物相组成和元素化合态. 结果表明, 离子注入后样品磨损量降低了77%. 耐磨损性能的明显改善归因于样品硬度增加, 磨损开始阶段保持低摩擦系数的时间较长和离子注入后合金固溶强化.     

Corrosion resistance of Al ion implanted AZ31 magnesium alloy at elevated temperature

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.     

Mechanical properties of carbon steel depending on the rate of the dose build-up of nitrogen and argon ions

The effect of pulsed irradiation with argons and nitrogen ions on the mechanical properties, morphology, and structure of the surface layers of carbon steel St3 (0.2% C, 0.4% Mn, 0.15% Si, and Fe for balance) has been investigated depending on the rate of dose build-up at an average ion current density of 10, 20, and 40 μA/cm². It has been established that the fatigue life and microhardness of surface layers increase in the entire studied range of dose build-up rates. This seems to be due to the hardening of the surface layers, which resulted from the generation of radiation defects and the irradiation-dynamic effect of fast ions. The sample irradiated by argon ions at the lowest of the selected dose build-up rates j _av = 10 μA/cm² withstands the largest number of cycles to failure.     

In vitro corrosion evaluation of nitrogen ion implanted titanium in simulated body fluid

Surface modification of commercially pure (CP) titanium was attempted by nitrogen ion implantation to investigate corrosion resistance in simulated body fluid. Nitrogen ion was implanted at 70 keV energy for different doses ranging from 5 × 10¹⁵ to 2.5 × 10¹⁷ ions/cm². In Vitro Open Circuit Potential (OCP-time measurements and cyclic polarization studies were carried out to evaluate the corrosion resistance of the implanted specimens with reference to the unimplanted one. Specimens implanted at 4 × 10¹⁶ and 7 × 10¹⁶ ions/cm² showed optimum corrosion resistance, and implantation beyond this dose deteriorated the corrosion resistance. Gracing Incidence X-ray diffraction (GIXD) was employed on implanted specimens to understand the phases formed with increasing doses. The results of the present investigation indicated that nitrogen ion implantation can be used as a viable method for improving corrosion resistance of titanium. Nature of the surface and reason for the variation and improvement in corrosion resistance are discussed in detail.     

Plasma nitriding of plastic mold steel to increase wear- and corrosion properties

In this study, the wear- and corrosion resistance of the layers formed on the surface of a precipitation hardenable plastic mold steel (NAK55) by plasma nitriding were investigated. Plasma nitriding experiments were carried out at an industrial nitriding facility in an atmosphere of 25% N₂ + 75% H₂ at 475 °C, 500 °C, and 525 °C for 10 h. The microstructures of the nitrided layers were examined, and various phases present were determined by X-ray diffraction. Wear tests were carried out on a block-on-ring wear tester under unlubricated conditions. The corrosion behaviors were evaluated using anodic polarization tests in 3.5% NaCl solution.The findings had shown that plasma nitriding does not cause the core to soften by overaging. Nitriding and aging could be achieved simultaneously in the same treatment cycle. Plasma nitriding of NAK55 mold steel produced a nitrided layer consisted of a compound layer rich in ε-nitride and an adjacent nitrogen diffusion layer on the steel surface. Increasing the nitriding temperature could bring about increase in the thickness of the nitrided layer and the nitride volume fraction. Plasma nitriding improved not only surface hardness but also wear resistance. The anti-wear property of the steel was found to relate to the increase in the thickness of the diffusion layer. Corrosion study revealed that plasma nitriding significantly improved corrosion resistance in terms of corrosion potential and corrosion rate. Improvement in corrosion resistance was found to be directly related to the increase in the nitride volume fraction at the steel surface.     

Hardness,wear and microstructure of carbon implanted AISI M2 high speed steel

The hardness, wear behaviour and microstructure of AISI M2 high speed steel implanted with carbon ions are discussed. The samples were implanted at an energy of 100 keV. The doses ranged from 1×10¹⁷ C⁺/cm² to 3×10¹⁸ C⁺/cm². Hardness increases due to ion implantation, but no significant dose dependence is found. For lower doses the wear effects mainly the pin, but from doses of 5×10¹⁷ C⁺/cm² onwards a pronounced ploughing of the disk is observed. The abrasive wear rate decreases with increasing dose. Microstructural investigations reveal the presence of ε-carbide and graphitic carbon in the implanted volume. A possible correlation between hardness and wear is discussed based on the microstructural results.     

Effect of nitrogen ion implantation dose on torsional fretting wear behavior of titanium and its alloy

Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO₂ ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.     

Effect of rate of dose build-up of manganese ions on changes in mechanical properties, morphology, and composition of surface layers of carbon steel

The effect of a dose build-up rate of 5 × 10¹⁶ ion/cm² under irradiation with manganese ions with an energy of 45 keV and at a current density of 10?C50 ??A/cm² on the mechanical properties, morphology, and composition of the surface layers of carbon steel St3sp has been investigated. It is shown that, among the dose build-up rates used, the optimal rate for surface hardening corresponds to an ion-current density of 10 ??A/cm². Based on these experimental data, a model of the processes that occur during the implantation of steel with Mn ions has been proposed.