Influence of Deposition Positions on Fretting Behaviors of DLC Coating on Ti-6Al-4V

Abstract

The influence of diamond-like carbon (DLC) coating positions—coated flat, coated cylinder, and self-mated coated surface tribopairs—on the fretting behaviors of Ti-6Al-4V were investigated using a fretting wear test rig with a cylinder-on-flat contact. The results indicated that, for tests without coating (Ti-6Al-4V–Ti-6Al-4V contact), the friction (Q_max/P) was high (0.8–1.2), wear volumes were large (0.08–0.1?mm³) under a large displacement amplitude of ±40 µm and small (close to 0) under a small displacement amplitude of ±20 µm, and the wear debris was composed of Ti-6Al-4V flakes and oxidized particles. For tests with the DLC coating, under low load conditions, the DLC coating was not removed or was only partially removed, Q_max/P was low (≤0.2), and the wear volumes were small. Under high load conditions, the coating was entirely removed, Q_max/P was high (0.6–0.8), and the wear volumes were similar to those in tests without coating. The wear debris was composed of DLC particles, Ti-6Al-4V flakes, and oxidized particles. The DLC coating was damaged more severely when deposited on a flat surface than when deposited on a cylindrical surface. The DLC coating was damaged more severely when sliding against a DLC-coated countersurface than when sliding against the Ti-6Al-4V alloy.     

Tribological Behaviour of Orthopaedic Ti-13Nb-13Zr and Ti-6Al-4V Alloys

The aim of this study is to compare the tribological behaviour of novel orthopaedic implant alloy Ti-13Nb-13Zr with that of the standard Ti-6Al-4V ELI alloy, available in four different microstructural conditions produced by variations in the heat treatments. The friction and wear tests were performed by using a block-on-disc tribometer in Ringer’s solution at ambient temperature with a normal load of 20–60 N and sliding speed of 0.26–1.0 m/s. It was found that variations in microstructures produced significant variations in the wear resistance of Ti-6Al-4V ELI alloy. The wear losses of materials solution treated (ST) above the β transus temperature are significantly lower compared with those of materials ST in the (α + β) phase field and are almost insensitive to applied load and sliding speed. Wear loss of the (α + β) ST Ti-6Al-4V ELI alloy continuously increased as applied load was increased and was highest at the highest sliding speed. The Ti-6Al-4V ELI alloy in all microstructural conditions possesses a much better wear resistance than cold-rolled Ti-13Nb-13Zr alloy. Friction results and morphology of worn surfaces showed that the observed behaviour is attributed to the predominant wear damage mechanism.     

Mechanical properties of the alloy Ti-6Al-4V irradiated with swift Kr ion

The radiation damage effect on the friction coefficient, wear, and microhardness of the alloy Ti-6Al-4V after 250 MeV krypton ion irradiation was studied. Tribological measurements were made in air, oxygen, and argon atmospheres and in a vacuum. The smallest friction coefficient for the irradiated samples occurred in argon and the vacuum. The wear of the unirradiated samples and those irradiated with low fluences (<10¹³ cm⁻²) increased in the vacuum and argon atmosphere. Wear was significantly reduced after irradiation with the fluence of 10¹⁴ cm⁻². The microhardness of the alloy Ti-6Al-4V increased by over 25% after irradiation with a large fluence.     

The Tribological Behavior of a Ti-46Al-2Cr-2Nb Alloy Under Liquid Paraffine Lubrication

The tribological behavior of a Ti-46Al-2Cr-2Nb alloy prepared by hot-pressed sintering was investigated under liquid paraffine lubrication against AISI 52100 steel ball in ambient environment and at varying loads and sliding speeds. For comparison, the tribological behavior of a common Ti-6Al-4V alloy was also examined under the same testing conditions. The worn surfaces of the two alloys were analyzed using a scanning electron microscope. The friction coefficient of the Ti-46Al-2Cr-2Nb alloy in the range of 0.13–0.18 was significantly lower than that of the Ti-6Al-4V alloy (0.4–0.5), but comparable to that under dry sliding, which indicated that TiAl intermetallics could be more effectively lubricated by liquid paraffine than titanium alloys. Applied load and sliding speed have little effect on the friction coefficient of the Ti-46Al-2Cr-2Nb alloy. The wear rate of the Ti-46Al-2Cr-2Nb alloy was about 45–120 times lower than that of Ti-6Al-4V alloy owing to Ti-6Al-4V alloy could not be lubricated effectively. The wear rate of the Ti-46Al-2Cr-2Nb alloy increased with increasing applied load, but decreased slightly at first and then increased with increasing sliding speed. The wear mechanism of the Ti-46Al-2Cr-2Nb intermetallics under liquid paraffine lubrication was dominated by main plowing and slight flaking-off, but that of the Ti-6Al-4V alloy was plastic deformation and severe delamination.     

The corrosion-wear behaviour of thermally oxidised CP-Ti and Ti-6Al-4V

The use of commercial purity titanium (CP-Ti) and Ti-6Al-4V alloys in bio-medical implant applications has been limited by their poor resistance to surface degradation processes. In this paper the corrosion-wear behaviour of untreated and thermally oxidised CP-Ti and Ti-6Al-4V have been compared. Oxidation of both alloys at 625 °C for 36 h resulted in the formation of an exterior layer of TiO₂ (rutile) that had a hardness ∼1000 HV. Corrosion-wear tests were made in reciprocation sliding contact with an α-Al₂O₃ ball immersed in physiological saline (0.89% NaCl) at room temperature. The oxidation treatment retarded the corrosion-wear of both CP-Ti and Ti-6Al-4V. For the untreated alloys, surface damage was dominated by micro-asperity shearing which resulted in rapid wear. Corrosion-wear of the oxidised materials was slower but more complex. The exterior TiO₂ layer formed on the oxidised Ti-6Al-4V alloy provided little protection, it was rapidly removed during the first 60 min of testing, by a process involving interfacial fracture. Conversely, the TiO₂ layer, albeit thinner, provided protection for the oxidised CP-Ti. Here, the layer becomes smoothly worn by a process that is proposed to be caused by the mechanical dissociation of the TiO₂-layer. For both oxidised titanium alloys the hardened oxygen diffusion zone (ODZ), formed beneath the TiO₂ layer, provided good protection from corrosion-wear. In both cases the ODZ was smoothly worn by a combination of abrasion and corrosion-wear processes. The latter process, termed Type I corrosion-wear, involves the repetitive mechanical degradation of the passive film that forms through aqueous corrosion. However, this is a relatively slow process.     

不同摩擦副条件下Ti-6Al-4V合金的微磨粒磨损行为

采用TE66微磨粒磨损实验机对医用Ti-6Al-4V钛合金在不同摩擦副条件下的微磨粒磨损行为进行研究,考察滑行距离、载荷对其微磨粒磨损的影响,通过观察磨斑形貌,分析其磨损机制。研究结果表明:Ti-6Al-4V合金的磨损量随滑移距离和载荷增加而增加,磨损率则相反,并且硬度较高的Si3N4陶瓷球对合金造成的磨损量和磨损率均低于ZrO2陶瓷球;在不同摩擦副条件下,随着滑行距离和载荷的增加,Ti-6Al-4V合金的磨损机制均由三体磨损转变为二三体混合磨损,所不同的是与Si3N4陶瓷球对摩时合金的混合磨损区域要少于与ZrO2陶瓷球对摩时。     

电弧离子镀沉积TiN/AlN-TiAlN复合膜的耐磨性

采用高纯铝、钛靶材,通过电弧离子镀工艺在TC4基材上沉积制备了TiN/AlN-TiAlN复合多层膜,用HV-1000型显微硬度计测试了膜层的硬度,用球盘磨损试验对比研究了膜层和基材的耐磨性。结果表明:膜层硬度为2856HV,耐磨性相比基材提高6倍以上。     

Comparative study on tribology and microhardness of laser synthesized Ti-Al2O3/Zn coatings on Ti-6Al-4V alloy

ABSTRACT

The study of laser cladding of 90Ti-10Al₂O₃, 90Ti-8Al₂O₃-2Zn and 90Ti-4Al₂O₃-6Zn coatings onto Ti-6Al-4V alloy, with intention to produce defect-less, high microhardness and wear resistant coating was carried out. The coatings were deposited onto Ti-6Al-4V alloy at 900 W laser power and 0.6 m/min laser scan speed. Microstructures and phase constituents of the developed coatings were investigated by using a scanning electron microscope (SEM) and X-ray diffractometer correspondingly. Vickers microhardness tester and pin-on-disk tribometer were employed to characterize microhardness and wear behaviour of the Ti-Al₂O₃/Zn coatings respectively. SEM was also used to examine the worn track. It was observed that 90Ti-10Al₂O₃ coating yielded optimal microhardness along with maximal wear resistance in comparison to the other coatings and Ti-6Al-4V alloy. It has been established that laser cladding of Ti-Al₂O₃ coating with Zn contents on Ti-6Al-4V alloy alleviates the formation of cracks, however, microhardness and wear properties are negatively affected.     

A study of the cutting-induced heating effect on the machined surface in ultra-precision raster milling of 6061 Al alloy

Ti-6Al-4V alloy is an attractive material in many industries due to its unique and excellent combination of strength to weight ratio and their resistance to corrosion. However, because of its low thermal conductivity and high chemical reactivity, Ti-6Al-4V alloy is generally classified as a difficult-to-cut material that can be characterized by low productivity and rapid tool wear rate even at conventional cutting speeds. It is well known that tool wear has a strong relationship with the cutting forces and a sound knowledge about correlation between cutting forces variation and tool wear propagation is vital to monitor and optimize the automatic manufacturing process. In the present study, high-speed end-milling of Ti-6Al-4V alloy with uncoated cemented tungsten carbide tools under dry cutting conditions is experimentally investigated. The main objective of this work is to analyze the tool wear and the cutting forces variation during high-speed end-milling Ti-6Al-4V alloy. The experimental results show that the major tool wear mechanisms in high-speed end-milling Ti-6Al-4V alloy with uncoated cemented tungsten carbide tools are adhesion and diffusion at the crater wear along with adhesion and abrasion at the flank wear. The cutting force component in the negative y-direction is more dominant of the three components and displays significantly higher magnitudes than that of the other two components in x- and z-directions. The variation of cutting force component F _y has a positive correlation with the tool wear propagation, which can be used as a tool wear indicator during automatic manufacturing process.     

Surface morphology in engineering applications: Influence of roughness on sliding and wear in dry fretting

Influence of initial surface roughness on friction and wear processes under fretting conditions was investigated experimentally. Rough surfaces (Ra=0.15-2.52 μm) were prepared on two materials: carbon alloy (AISI 1034) and titanium alloy (Ti-6Al-4V). Strong influence of initial surface roughness on friction and wear processes is reported for both tested materials. Lower coefficient of friction and increase in wear rate was observed for rough surfaces. Wear activation energy is increasing for smoother surfaces. Lower initial roughness of surface subjected to gross slip fretting can delay activation of wear process and reduce wear rate; however, it can slightly increase the coefficient of friction.     

Assessment of the machinability of Ti-6Al-4V alloy using the wear map approach

The high strength to density ratio of titanium alloys coupled with excellent corrosion resistance even at elevated temperatures make them ideal for aerospace applications. Moreover, the biocompatibility of titanium also enables its widespread use in the biomedical and food processing industries. However, the difficulty in machining titanium and its alloys along with the high cost of its extraction from ore form presents a major economic constraint. In the context of machining economics, the wear map approach is very useful in identifying the most suitable machining parameters over a feedrate–cutting velocity plane. To date, wear maps have only been prepared for the machining of ferrous alloys. In this article, a review of the machinability of Ti-6Al-4V alloy is presented with emphasis on comparing the wear performance of various tool materials. In addition, a new wear map for Ti-6Al-4V alloy is presented based on unified turning tests using H13A grade carbide inserts. This wear map can be used as a guide in the selection of cutting variables that ensure the least tool wear rates. This article contrasts the occurrence of a safety zone in the case of machining steels to that of an avoidance zone for Ti-6Al-4V alloy.     

Laser cladding of ti-6al-4v with bn for improved wear performance

Titanium and its alloys suffer from galling, seizing, ploughing and adhesion during sliding contacts. A laser-cladding method, to enhance the wear performance of titanium, was investigated. A 1.5 kW continuous-wave CO₂ gas laser was used to clad hexagonal BN powder with and without the addition of NiCrCoAlY on a Ti-6Al-4V alloy substrate. X-ray diffraction, scanning electron microscopy, optical metallography, and Vickers' micro-hardness tests were employed to characterize the clad layers. A pin-on-block reciprocating wear machine was used to evaluate the sliding wear characteristics of age-hardened, laser surface-melted and laser-clad Ti-6Al-4V alloys. Results indicated that the clad layers consisted of TiN, TiB₂, and various alloy phases. Claddings with excellent adhesion and thicknesses up to 600 μm, with a maximum hardness of 1600 HV, were obtained. Wear tests showed a substantial improvement (10–200 times) in wear resistance of claddings over age-hardened and surface-melted layers. The improved wear performance is attributed to the high hardness and low friction properties of clad layers.     

Tool wear in turning of titanium alloy after thermohydrogen treatment

The influence of hydrogen contents on the tool wear has been mainly focused on the flank wear of the common tool,and the influence of hydrogen contents on the rake crater wear(main wear type) of the tool,particularly for the fine granular material tool,has been less investigated comprehensively.In this paper,for the purpose of researching the influence of hydrogen contents on tool wear,the titanium alloy Ti-6Al-4V is hydrogenated at 800 ℃ by thermohydrogen treatment technology and the turning experiments are carried out by applying uncoated WC-Co cemented carbide tool.The three-dimensional video microscope is used to take photos and measure tool wear.The results show that both of crater wear depth(KT) and average flank wear width(VB) firstly decreases and then increases with the increasing of hydrogen content.The maximum reducing amplitude of KT and VB is about 50% and 55%,respectively.Under the given conditions,the optimum hydrogen content is 0.26%.It is considered that the reduction of cutting temperature is an important factor for improving tool wear after the Ti-6Al-4V alloy is properly hydrogenated.Furthermore,the reasons of hydrogen effect on the tool wear are chiefly attributed to comprehensive effect of hydrogen contents on microstructure,physical properties and dynamic mechanical properties of the Ti-6Al-4V alloy.The proposed research provides the basic data for evaluating the machinability of hydrogenation Ti-6Al-4V alloy,and promotes practical application of thermohydrogen treatment technology in titanium alloys.     

Investigation on diffusion wear during high-speed machining Ti-6Al-4V alloy with straight tungsten carbide tools

During high-speed machining Ti-6Al-4V alloy, high-temperature at the tool–chip interface and the concentration gradient of chemical species between tool material and workpiece material support the activation of diffusion process, and therefore the crater wear forms on the rake surface of the cutting tool at a short distance from the cutting edge. In this paper, the diffusion analysis was theoretically proposed. The constituent diffusion at the contact interface between tool material and Ti-6Al-4V alloy at high-temperature environment, the crater wear on the rake surface of the tool, and the chips collected from high-speed milling Ti-6Al-4V alloy with straight tungsten carbide tools were analyzed by the scanning electron microscope with energy dispersive X-ray spectroscopy. The constituents inside the tool could diffuse into the workpiece and the diffusion layer was very thin and close to the interface. Compared with the diffusion of tungsten and carbon atoms, the pulling out and removing of the tungsten carbide (WC) particles due to cobalt diffusion dominated the crater wear mechanism on the rake surface of the cutting tool.     

Sliding wear behaviour of ion implanted ultra high molecular weight polyethylene against a surface modified titanium alloy Ti-6Al-4V

A study has been made of the sliding wear behaviour of untreated and ion implanted ultra high molecular weight polyethylene (UHMWPE) against a surface modified titanium alloy (Ti-6Al-4V) using a pin on disc apparatus. It was found that the presence of water lubrication and a very smooth counterface was necessary to maintain low wear rates of the UHMWPE. A ‘zero wear’ effect was observed when nitrogen implanted UHMWPE was tested against very smooth counterfaces (R_a ≈ 0.03 μm) of either surface oxidized or nitrogen implanted Ti-6Al-4V under water lubrication. The enhanced mechanical and physical properties of the surface treated materials are believed to be responsible for the improved wear performance.     

Corrosive Wear and Mechanical Properties of Ni/Al2O3 Micro- and Nanoparticulates-Reinforced Coatings on Ti-6Al-4V Alloy

Nanocomposite coatings can endow a plated surface with various properties such as wear resistance, high-temperature corrosion protection, oxidation resistance, and self-lubrication. This work studies the corrosion and corrosive wear resistance of electroplated nickel nanocomposite coatings on Ti-6Al-4V alloy in a Hank's solution, adding various concentrations of an Al₂O₃ powder in plating solution, with particle diameters of 20–30 nm and 1 μm for comparisons. The experimental results showed that the content of Al₂O₃ incorporated into the electroplated nickel composite coating increased with the concentration of Al₂O₃ powder in the electroplating solution, and increasing the surface hardness, corrosion, and corrosive wear resistance of electroplated nickel micro- and nanocomposite coatings caused smearing of the nodule boundary and elimination of voids in the deposits. The Al₂O₃ nanoparticulates were embedded and distributed more uniformly than the Al₂O₃ microparticulates in the nickel matrix after a heat treatment of 400°C, producing a more continuous and dense coated composite layer on the Ti-6Al-4V substrate. This phenomenon is responsible for the Ni/Al₂O₃ composite coating with superior surface hardness, providing high corrosion resistance and corrosive wear protection to the Ti-6Al-4V alloy substrate in Hank's solution.     

Influence of Rapidly Solidified Structures on Wear Behavior of Ti-6AI-4V Laser Alloyed with TiC

In this paper the influence of rapidly solidified structures on the wear behavior of Ti-6Al-4V laser alloyed with TiC is studied by using an unlubricated sliding wear test. The results show that laser surface alloying with TiC can significantly increase wear resistance of Ti-6Al-4V. The wear of Ti-6Al-4V is characterized by adhesive de-lamination and melting showing a severe wear mechanism, while after alloying with TiC, it is changed into a mild wear mechanism characterized by a smooth, worn surface. This is attributed to directional fast-growing dendrites capped by a TiN/TiC film with high hardness and framed α marlensites obtained in rapid solidification.     

A comparative evaluation of the wear of ultra-high molecular weight polyethylene abraded by Ti-6Al-4V

The study was initiated to assess the suitability of Ti-6Al-4V as a metal which articulates against Ultra High Molecular Weight (UHMW) polyethylene in total joint applications. The wear surfaces of Ti alloy were prepared to different levels of surface roughness and the effect of various surface chemical treatments were examined. A specially designed annular contact laboratory wear tester was developed to provide the surface loading and articulation. Comparative tests were also performed using 316 LVM stainless steel and Co-Cr-Mo alloy metallic wear components. All annular contact wear tests were performed in mammalian Ringer's solution environments and were evaluated using standard statistical techniques. Scanning electron microscope (SEM) analysis of the wear surfaces indicates the formation of a polyethylene transfer film on all metal surfaces. The surface of the UHMW polyethylene samples after testing was considerably rougher than the original articulating metallic surface; the transfer film on the metal surfaces was responsible for this. It was concluded that Ti-6Al-4V is satisfactory for total joint replacement when used in combination with UHMW polyethylene. Proper surface preparation may allow lower rates of wear than conventional orthopaedic alloys.     

Response of Ti–6Al–4V and Ti–24Al–11Nb alloys to dry sliding wear against hardened steel

Titanium alloys have been of great interest in recent years because of their very attractive combination of high strength, low density and corrosion resistance. Application of these alloys in areas where wear resistance is also of importance calls for thorough investigations of their tribological properties. In this work, Ti–6Al–4V and Ti–24Al–11Nb alloys were subjected to dry sliding wear against hardened-steel counter bodies and their tribological response was investigated. A pin-on-disc type apparatus was used with a normal load of 15–45N and sliding speed of 1.88 ms⁻¹. In the steady state, it was demonstrated that Ti–24Al–11Nb had a substantially higher wear resistance (about 48 times) than that of the Ti–6Al–4V alloy tested under a normal load of 45 N. Severe delamination is found to be responsible for the low wear resistance of Ti-6Al-4V. In the case of Ti–24Al–11Nb, two wear mechanisms have been suggested: delamination with a lower degree of severity and oxidative wear. It is thought that the ability of Ti–24Al–11Nb to form a protective oxide layer during wear results in a much lower wear rate in this alloy.     

Effect of grain refinement and modification on the dry sliding wear behaviour of eutectic Al-Si alloys

The present study deals with an investigation of dry sliding wear behaviour of grain refined and or modified eutectic (Al-12Si) Al-Si alloy by using a Pin-On-Disc machine. The indigenously developed Al-1Ti-3B and Al-10Sr master alloys were used as grain refiner and modifier for the grain refinement of α-Al dendrites and modification of eutectic Si, respectively. Various parameters have been studied such as alloy composition, sliding speed, sliding distance and normal pressure. The cast alloys, master alloys and worn surfaces were characterized by SEM/EDX microanalysis. Results suggest that, the wear resistance of eutectic Al-Si alloys increases with the addition of grain refiner (Al-1Ti-3B) and or modifier (Al-10Sr). Further, the worn surface studies show that adhesive wear was observed in Al-12Si alloy in the absence of grain refiner and modifier. However, an abrasive and oxidative wear was observed when the grain refiner and modifier are added to the same alloy. Commercially available LM-6 (12.5%Si) alloy was used for comparison.