Application of ion implantation to improve the wear resistance of 52100 bearing steel

Bearings fabricated from 52100 steel are susceptible to adhesive wear which results in reduced performance of arrospace system components. To improve the wear resistance of 52100 steel, implantation of titanium ions was performed. Ion- implanted surfaces were characterized by electron microscopy and Auger electron spectroscopy.Wear tests, using the load-friction-wear technique, showed a 24% decrease in the breakaway coefficient of friction and an 11% decrease in the saturated value for titanium-implanted specimens as well as a modification of the adhesive wear behavior.     

Établissement par spectrométrie Auger d'un profil de concentration dans une interface épitaxique: Cas du couple AuAg

In this paper we present the results of our study of the depth profile of the concentration of AuAg and AgAu bilayers using Auger electron spectroscopy during ionic sputtering. We demonstrate a new way of performing the transformation of the graph representing the height of the Auger peaks versus sputtering time to a graph representing concentration versus depth. This profile allows us to find the AuAg interdiffusion coefficient and to note the shift of the interface C = 0.5.     

Effect of titanium implantation on the friction and surface chemistry of a Co-Cr-W-C alloy

The effects of the implantation of titanium ions, to a fluence of 5 × 10¹⁷ Ti ions cm^-2 at 190 keV, on the tribological behavior of a centrifugally cast cobalt-based alloy (Stoody 3) were investigated by friction tests against a variety of alloy and carbon counterfaces. Dry sliding friction coefficients were compared with those made on similarly prepared, but non-implanted, and fatty-acid-coated samples. High friction coefficients (μ_K ≈ 0.6) for the alloy-Stoody 3 couples coincided with the formation of debris, with the same composition as the softer of the mating alloys, in the wear scars. Much lower μ_K values were measured on titanium-implanted (μ_K ≈ 0.25) and acid-coated (μ_K ≈ 0.1) surfaces. Optical microscopy indicated a change in the surface texture of the implanted surfaces attributable to sputtering. Auger spectroscopy showed that vacuum carburization of both carbide and matrix phases of the Stoody alloy occurred during implantation. The friction and wear mechanisms involved are discussed.     

Abrasion resistance,microhardness and microstructures of single-phase niobium nitride films

The relative abrasive wear resistance of single-phase niobium nitride films deposited at 900 and 500 °C was measured. Wear resistance versus depth profiles of films abraded against 1–5 μm diamond were obtained by weight loss methods. A β phase Nb₂N film was five to 20 times more abrasion resistant, but only slightly (40%) harder, than the σ phase NbN films made at the same temperature. The β-N₂N film was deformed plastically during wear, reorienting the [002] c axis perpendicular to the plane of the substrate. The abrasion resistance of the σ-NbN films was initially proportional to the microhardness. Two films had changes in their abrasion resistance as wear proceeded: for one film the change was attributable to deviations in stoichiometry and for the other film it was attributable to increased lattice distortion.     

Characterization of ion beam modified ceramic wear surfaces using Auger electron spectroscopy

An investigation of the surface chemistry and morphology of the wear surfaces of ceramic material surfaces modified by ion beam mixing has been conducted using Auger electron spectroscopy and secondary electron microscopy. Studies have been conducted on ceramic/ceramic friction and wear couples made up of TiC and NiMo-bonded TiC cermet pins run against Si₃N₄ and partially stabilized zirconia disc surfaces modified by the ion beam mixing of titanium and nickel, as well as unmodified ceramic/ceramic couples in order to determine the types of surface changes leading to the improved friction and wear behaviour of the surface modified ceramics in simulated diesel environments. The results of the surface analyses indicate that the formation of a lubricating oxide layer of titanium and nickel, is responsible for the improvement in ceramic friction and wear behaviour. The beneficial effect of this oxide layer depends on several factors, including the adherence of the surface modified layer or subsequently formed oxide layer to the disc substrate, the substrate materials, the conditions of ion beam mixing, and the environmental conditions.     

Reinforcing effect of carbon nanotubes on PEEK composite filled with carbon fibre

Abstract

The main objective of the present paper is to develop high wear resistance carbon fibre reinforced polyether ether ketone composite with addition of multiwall carbon nanotubes. These compounds were well mixed in a batch mixer, and compounded polymers were fabricated into sheets of known thickness by compression moulding. Samples were tested for wear resistance with respect to different concentration of fillers. The wear resistance properties of these samples depend on filler aspect ratio. Wear resistance of composite with 20 wt-% of carbon fibre increases when multiwall carbon nanotubewas introduced. The worn surface features have been examined using scanning electron microscope. Photomicrographs of the worn surfaces revealed higher wear resistance with the addition of carbon nanotube. Also better interfacial adhesion between carbon and vinyl ester in carbon reinforced vinyl ester composite was observed.     

New plasma surface-treated memory alloys: Towards a new generation of “smart” orthopaedic materials

This paper describes the corrosion resistance, surface mechanical properties, cyto-compatibility, and in-vivo performance of plasma-treated and untreated NiTi samples. Nickel–titanium discs containing 50.8% Ni were treated by nitrogen and carbon plasma immersion ion implantation (PIII). After nitrogen plasma treatment, a layer of stable titanium nitride is formed on the NiTi surface. Titanium carbide is also found at the surface after carbon plasma implantation. Compared to the untreated samples, the corrosion resistances of the plasma PIII samples are better by a factor of five and the surface hardness and elastic modulus are better by a factor of two. The concentration of Ni leached into the simulated body fluids from the untreated samples is 30 ppm, whereas that from the plasma-treated PIII are undetectable. Although there is no significant difference in the ability of cells to grow on either surface, bone formation is found to be better on the nitrogen and carbon PIII sample surfaces at post-operation 2 weeks. All these improvements can be attributed to the formation of titanium nitride and titanium carbide on the surface.     

Selected area and in-depth auger analysis of thin films

Auger electron spectroscopy (AES) has rapidly developed from a purely research oriented technique into an extremely versatile analytical method with unique features for qualitative and quantitative materials characterization. The low escape depth (5–10 Å) of the emitted Auger electrons makes it ideal for surface analysis and for depth profile impurity distribution analysis when combined with in situ ion sputtering.Both surface and depth profile analysis can be accomplished on a selected area by the use of optical or primary electron beam scanning techniques. Results are presented which illustrate the significance of the analytical capabilities of AES in the qualitative and quantitative analysis of thin film electronic materials used in the fabrication of precision thin film resistors, capacitors and conductors.     

Improvement of metal properties by ion implantation

Ion implantation is being investigated as a technique for the beneficial modification of surface-sensitive and life-limiting properties of metals including resistance to wear and fatigue. Ion implantation is a process of accelerating ions to high velocities and directing them into the near-surface regions of materials (e.g. alloys) to produce in essence a different material (alloy) in the near-surface region. Ion implantation can produce a graded alloy from the surface to the unchanged underlying bulk alloys so that both the surface and the bulk alloys can be independently optimized. The implanted layer is typically hundreds to thousands of ångströms deep with implanted atom concentrations of up to fifty atomic per cent or more. The sliding-wear rate between various steel alloys was significantly reduced by implanting one of the surfaces with selected elemental species such as nitrogen, carbon and titanium. Experiments were conducted on a number of materials including stainless steel, too steel, bearing alloys and silicon nitride. The implantation technique has also been reported to increase fatigue lifetimes in low-carbon steel by a factor of 50–100. Experimentation is now being directed towards other materials of major technological interest such as titanium alloys. The effect of ion implantation on (1) the wear and fatigue properties and (2) the microstructural characteristics of implanted materials with selected examples is discussed.     

TiC coatings deposited onto carbon and molybdenum surfaces by electron beam evaporation

TiC coatings were deposited onto graphite and molybdenum substrates by an electron beam evaporation method. A titanium film 1000–10000 Å thick was evaporated onto the graphite substrate which was then heated at 1000 °C for 5 min to form the TiC film by an interdiffusion process. In the case of the molybdenum substrate, a double-layer film consisting of titanium and carbon (Ti/C/Mo) was prepared by evaporation and the subsequent heat treatment was performed at 700 °C or at 1000 °C for 5 min. The properties of the coatings were examined by various surface analysis techniques including Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Rutherford backscattering (RBS). The atomic ratio of carbon to titanium in these coatings was found to be 0.9. The in-depth profiles obtained by XPS examination showed that the coating prepared at 700 °C had a carbon layer between the TiC layer and the molybdenum substrate, while that prepared at 1000 °C had an Mo₂C layer between the coating and the substrate.     

Ti+注入H13钢的注入层研究

Ti (10 0kV ,3× 10 17cm- 2 )注入H13钢 ,表面注入层的化学组成和微观结构发生了很大的变化。俄歇分析表明 ,注入元素Ti在钢表面层的剖面浓度分布呈近似高斯分布 ,在 4 0nm处Ti的浓度达到最大值。离子束真空碳化导致在钢的表面形成一层约 2 0nm的“富碳层”。透射电镜分析表明 ,表面层的微观形貌由注入前的板条状马氏体结构转变成注入后的微胞状结构。电子衍射则证实 ,表面注入层已出现非晶化 ,并且有约 5nm的TiC颗粒析出。摩擦磨损实验进一步表明 ,注入后钢的摩擦系数降低 70 % ,磨损率降低 98%。     

The effects of N+ implantation on the wear and friction of type 304 and 15-5 PH stainless steels

Ion implantation of N⁺ into mechanically polished type 304 and 15-5 PH stainless steels was studied to determine its effect on dry wear and friction behavior. Implantation of 4.0 × 10¹⁷ N⁺ cm^-2 at 50 keV yielded a depth profile with a peak concentration of about 45 at.% at a depth of 70 nm which dropped to about 10 at.% at 120 nm. Wear and friction were studied in an unlubricated pin-on-disc configuration using type 304 and 440C stainless steel pins. Both N⁺-implanted steels exhibited reduced wear at low loads but no significant reduction in the coefficient of friction was found. At the lowest normal load studied (12.3 gf), the average maximum wear depth of the implanted 15-5 PH stainless steel disc (about 0.1 μm) was reduced to approximately 10% of that for the corresponding unimplanted pin-on-disc pair after 1000 cycles. At normal loads of 50 gf or above (corresponding to hertzian stresses of 1160 MPa or higher) all beneficial effects were gone. Vacuum heat treatment at 923 K for 1.8 ks of an identically implanted type 304 stainless steel specimen eradicated the benificial effects of the nitrogen implantation. The N⁺-implanted discs show similar reductions in wear to discs implanted with titanium and carbon, but the N⁺-implanted discs do not exhibit the reductions in the coefficient of friction seen with the discs implanted with titanium and carbon.     

Mechanical characterization of anti-infectious,anti-allergic,and bioactive coatings on orthopedic implant surfaces

In total joint replacement much effort has been made to reduce implant loosening. We investigated different implant coatings (copper integrated titanium dioxide (TiO₂–Cu), titanium nitride (TiN), plasma polymerized allylamine (PPAAm), and calcium phosphate (CaP)) regarding the adhesion strength and wear resistance. Standardized scratch and adhesive tests were applied. Abrasive wear was measured with artificial bone and bone cement using a special testing machine. All tested coatings have higher bonding strengths than the 22 N/mm² required for medical implant surface coatings by ASTM standard 4711-F. Using bone cement, wear testing revealed higher wear rates in most cases. Polished surfaces reduce the amount of wear, whereas rough surfaces highly increase the wear rate due to three-body wear, especially ceramic surfaces. In general, the application of bone cement in conjunction with modified implant surfaces can lead to an increase in wear rate.     

Study of aeroabrasive wear of hot-pressed materials of the B4C-TiB2 system

The results of the studies of aeroabrasive wear of hot-pressed materials of the B₄C-TiB₂ system at different angles of abrasive particles attacks have been considered. It has been shown that the materials wear resistance is essentially affected by the relation of phases in the composite. The formation of 5–10 wt % titanium diboride in a B₄C composite have been defined to provide a high wear resistance because of the increase of the fracture toughness K _Ic from 3.8 to 4.4 MPa·m^1/2 on retention of the high hardness (H _V = 20–23 GPa).     

Research on new rapid and deep plasma nitriding techniques of AISI 420 martensitic stainless steel

Cyclic plasma oxynitriding and cyclic plasma nitriding catalyzed by rare earth La of AISI 420 martensitic stainless steel were performed and compared with conventional plasma nitriding. The nitrided layers were investigated by means of an optical microscope, microhardness tester, Auger electron spectroscopy (AES), X-ray diffraction (XRD), wear machine, scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that the wear resistance of AISI 420 martensitic stainless steel is improved significantly by the two new rapid and deep plasma nitriding techniques. The new techniques increase the surface hardness of the nitrided layers and make the microhardness profiles gentler, which are consistent with the nitrogen concentration depth profiles. Meanwhile, the nitrided effect improves with increasing cycles. It was also found that the optimum phase compositions of nitrided layers with more γ′ phases and less ? phases for long-term service conditions can be obtained by the two new techniques, which is in agreement with the microstructure. In addition, traces of Fe₃O₄ were found in the cyclic plasma oxynitrided sample. Combining the SEM and EDS analysis indicated the existence of La in the nitrided layer of the sample under cyclic plasma nitriding catalyzed by rare earth La.     

Microstructure and properties of composite (B + C) diffusion layers on low-carbon steel

Combined surface hardening with boron and carbon was used for low-carbon 5120 steel. The microstructure, carbon profiles and chosen properties of borided layers produced on the carburized 5120 steel have been examined. These composite (B + C) layers are termed borocarburized layers. The microhardness profiles and wear resistance of these layers have been studied. In the microstructure of the borocarburized layer two zones have been observed: iron borides (FeB + Fe₂B) and a carburized layer. It has been found the depth (100–125 m) and microhardness (1500–1900 HV) of iron borides zone. The carbon content (0.83–1.46 wt pct) and microhardness (950 HV) beneath iron borides zone have been determined. The microhardness gradient in borocarburized layer has been reduced in comparison with the only borided layer. An increase of distance from the surface is accompanied by a decrease of carbon content and microhardness in the carburized zone. The carbon and microhardness profiles of borided, carburized and borocarburized layers have been presented. A positive influence of composite layers (B + C) on the wear resistance was determined. The wear resistance of the borocarburized layer was determined to be greater in comparison with that for only borided or only carburized layers.     

The effect of amorphous silicon capping on titanium during TiSi2 formation by RTA

Thin film reactions of the Ti/(1 0 0)Si structure and the amorphous-Si/Ti/(1 0 0)Si structure are performed by rapid thermal annealing (RTA) in argon at temperatures of 500–800° C. Auger depth profiling shows that the as-deposited titanium film of the Ti/(1 0 0)Si structure and the as-deposited amorphous silicon (a-Si) film of the a-Si/Ti/(1 0 0)Si structure exhibit a roughly exponential oxygen distribution decreasing from the surface when exposed to air. An electronic spectroscopy for chemical analysis (ESCA) shows that the oxygen in the a-Si film forms Si0₂ and the oxygen in the titanium film forms titanium oxide. For the Ti/(1 0 0)Si structure, the oxygen tends to be redistributed uniformly throughout the titanium film near the onset of silicide formation during RTA. As silicide formation progresses, the redistributed oxygen is snowplowed back toward the surface owing to oxygen solubility difference between Ti and TiSi₂. Consequently, the oxygen concentration in the unreacted titanium layer increases. This increased oxygen concentration retards the silicide growth even though there remains an unreacted titanium layer. The oxygen redistribution in the titanium film correlates well with the rapid increases in the sheet resistance near the onset of silicide formation. When a-Si is sputter-deposited sequentially on the titanium film without breaking the vacuum, the oxygen in a-Si is not redistributed during RTA. Thus there is no rapid increase in the sheet resistance, and the saturated sheet resistance is lower than that of Ti/(1 0 0)Si structure. The reason is that the conversion of deposited titanium film into TiSi₂ is made completely because the a-Si film on the titanium film prevents oxygen infiltration into the titanium film.     

Effect of particulate additions on the contact damage resistance of hot-pressed Si3N4

Silicon nitride matrix composites containing particles of SiC, TiC, and BN were fabricated and tested for improved contact damage resistance at 900° C in an oxidizing atmosphere. Contact damage resistance was characterized with profilometry, scanning electron microscopy, bend tests, and coefficient of friction measurements. The results of these tests indicated that composites containing TiC particles showed dramatically improved friction and wear behaviour compared to the SiC- and BN-containing composites, as well as the monolithic Si₃N₄. Auger spectroscopy indicated that the improved behaviour was due to the formation of a lubricious oxide containing both titanium and silicon on the surface of the composite and the transfer of some of the oxide to the rider.     

The effect of different methods to add nitrogen to titanium alloys on the properties of titanium nitride clad layers

In this investigation, titanium nitride (TiN) reinforcements are synthesized in situ on the surface of Ti–6Al–4V substrates with gas tungsten arc welding (GTAW) process by different methods to add nitrogen, nitrogen gas or TiN powder, to titanium alloys. The results showed that if nitrogen gas was added to titanium alloys, the TiN phase would be formed. But if TiN powder was added to titanium alloys, TiN + TiN_x dual phases would be presented. The results of the dry sliding wear test revealed that the wear performance of the Ti–6Al–4V alloy specimen coated with TiN or TiN + TiN_x clad layers were much better than that of the pure Ti–6Al–4V alloy specimen. Furthermore, the evolution of the microstructure during cooling was elucidated and the relationship among the wear behavior of the clad layer, microstructures, and microhardness was determined.     

Effect of shotpeening on sliding wear and tensile behavior of titanium implant alloys

Titanium has good biocompatibility and so its alloys are used as implant materials, but they suffer from having poor wear resistance. This research aims to improve the wear resistance and the tensile strength of titanium alloys potentially for implant applications. Titanium alloys Ti–6Al–4V and Ti–6Al–7Nb were subjected to shotpeening process to study the wear and tensile behavior. An improvement in the wear resistance has been achieved due to surface hardening of these alloys by the process of shotpeening. Surface microhardness of shotpeened Ti–6Al–4V and Ti–6Al–7Nb alloys has increased by 113 and 58 HV_(0.5), respectively. After shotpeening, ultimate tensile strength of Ti–6Al–4V increased from 1000 MPa to 1150 MPa, higher than improvement obtained for heat treated titanium specimens. The results confirm that shotpeening pre-treatment improved tensile and sliding wear behavior of Ti–6Al–4V and Ti–6Al–7Nb alloys. In addition, shotpeening increased surface roughness.