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.     

Influence of Al2O3 reinforcement on the abrasive wear characteristic of Al2O3/PA1010 composite coatings

In the present study, the abrasive wear characteristics of Al₂O₃/PA1010 composite coatings were tested on the turnplate abrasive wear testing machine. Steel 45 (quenched and low-temperature tempered) was used as a reference material. The experimental results showed that when the Al₂O₃ particles have been treated with a silane coupling agent (γ-aminopropyl-triethoxysilane), the abrasive wear resistance of Al₂O₃/PA1010 composite coatings has a good linear relationship with the volume fraction of Al₂O₃ particles in Al₂O₃/PA1010 composite coatings and the linear correlation coefficient is 0.979. Under the experimental conditions, the size of Al₂O₃ particles (40.5-161.0 μm) has little influence on the abrasive wear resistance of Al₂O₃/PA1010 composite coatings. By treating the surface of Al₂O₃ particles with the silane coupling agent, the distribution of Al₂O₃ particles in PA1010 matrix is more homogeneous and the bonding state between Al₂O₃ particles and PA1010 matrix is better. Therefore, the Al₂O₃ particles make the Al₂O₃/PA1010 composite coatings have better abrasive wear resistance than PA1010 coating. The wear resistance of Al₂O₃/PA1010 composite coatings is about 45% compared with that of steel 45.     

Tribological and corrosion behaviors of Al2O3/polymer nanocomposite coatings

In this paper, the tribological and electrochemical corrosion properties of Al₂O₃/polymer nanocomposite coatings were studied by using micro-hardness test, single-pass scratch test, abrasive wear test, and finally electrochemical technique such as potentiodynamic polarization measurement. The coatings containing Al₂O₃ nanoparticles showed improvement in scratch and abrasive resistance compared with that of polymer coating. The improvement in scratch and abrasive resistance is attributed to the dispersion hardening of Al₂O₃ nanoparticles in polymer coatings. Corrosion test results showed that the embedded Al₂O₃ nanoparticles in polymer matrix do not sacrifice the corrosion resistance of the polymer itself.     

Novel investigation on tribological properties of Ni–P–Ag–Al2O3 hybrid nanocomposite coatings

In this research, silver and alumina particles were co-deposited within Ni–P matrix to obtain Ni–P–Ag–Al₂O₃ hybrid coating. The structure of coatings was analyzed by X-ray diffraction and the tribological properties of deposits were evaluated by pin on disc tribometer. 3D optical profiler and scanning electron microscopy were used to study wear rate and worn surfaces. The results showed that Ni–P–Ag and Ni–P–Ag–Al₂O₃ coatings have the self-lubrication property and maximum hardness (∼1310 HV) and wear resistance were obtained for Ni–P–Al₂O₃ coating. Also, Ni–P–Ag–Al₂O₃ hybrid nanocomposite coating had higher wear resistance than Ni–P and Ni–P–Ag coatings. Moreover, the best conditions was achieved for heat treated hybrid coating in the concentration of 30 mg/L silver and 150 mg/L alumina in the plating solution.     

The Wear Resistance of HVOF Sprayed Composite Coatings

The aim of the study was to determine the interactions between standard antiwear zinc dialkyldithiophosphate (ZDTP)-type additives and composite coatings containing hard phases of Al₂O₃, SiC, and TiN in the nickel matrix. The analysis was conducted for selected ceramic materials with different structures and different tribological behavior of ionic, covalent, and metallic bonds. The composite coatings were deposited on C45 steel using the high-velocity oxygen-fuel (HVOF) process. This process efficiently uses high kinetic energy and controlled thermal output to produce dense, low porosity coatings with highly predictable chemistries that are homogeneous in structure. The coatings can operate under harsh service conditions, because they are characterized by higher durability and higher wear and corrosion resistance. It was necessary to determine the interactions between the ZDTP-type antiwear additives (zinc dialkyldithiophosphates) and the coatings. The tribological properties of nickel and nickel-based composite coatings were examined by means of a T-01 M tester functioning in the ball-on-disc configuration during technically dry friction and boundary lubricated friction with lubricants containing 1% ZDTP. The comparative analysis confirmed different tribochemical activity and, accordingly, different tribological effectiveness of the nickel and nickel-based composite coatings during friction.     

Metal transfer and wear in fine grinding

The transfer and wear characteristics of two widely used abrasive materials (A1₂O₃ and SiC) are studied when grinding two difficult materials (AISI T15 tool steel and Ti-6Al-4V titanium alloy). A newly developed accelerated wear technique (cluster overcut flygrinding) is employed together with Auger electron spectroscopy, X-ray diffraction and scanning transmission electron microscopy. Experimental results suggest that when grinding steel the wear of SiC is primarily due to oxidation, while the wear of Al₂O₃ is primarily due to metal build-up, resulting in microchipping. When a titanium alloy is being ground, both types of abrasive result in a microchipping type of wear, the rate of which decreases when the wheel speed is reduced.     

Synergism between corrosion and wear on CoCrMo−Al2O3 biocomposites in a physiological solution

The use of metal matrix composite structures in biomedical implants can be a solution for decreasing the amount of degradation products. Thus, the present work aims to investigate the synergism between corrosion and wear on CoCrMo matrix 10% (vol) Al₂O₃ particle reinforced composites in phosphate buffer solution (PBS) at body temperature. Corrosion behavior was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization. Tribocorrosion tests were performed under open circuit potential, as well as under cathodic and anodic potentiostatic conditions using a reciprocating ball-on-plate tribometer. Results suggest that the addition of Al₂O₃ particles did not create a significant effect on corrosion behavior of CoCrMo alloy, however, it increased the wear resistance and decreased the corrosion kinetics when sliding in PBS solution.     

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.     

Wear and abrasion of cast Al-Alumina particle composites

Wear rates for cast aluminium and Al-Si alloys containing up to 5 wt.% γ-Al₂O₃ particles (100 μm size) were determined under conditions of adhesive wear and abrasive wear against a hardened steel disc and an alumina abrasive cloth sheet respectively. The adhesive wear rate of aluminium containing 5 wt.% A1₂O₃ dispersions is similar to that of Al-11.8Si eutectic alloy and slightly higher than that of A1-16Si hypereutectic alloy. Al-3wt. %Al₂O₃ and Al-5wt.%Al₂O₃ composites perform better than Al-11.8Si and Al-16Si hypereutectic alloys under abrasive wear conditions. Al-11.8Si and Al-16Si alloys have a lower abrasive wear resistance than pure aluminium. The results indicate that Al₂O₃ particles can be used as a substitute for silicon as the hard dispersed phase in aluminium for wear-resistant and abrasion-resistant applications.     

Wear and corrosion behavior of electrodeposited nickel–carbon nanotube composite coatings on Ti–6Al–4V alloy in Hanks′ solution

Carbon nanotubes (CNT) have received considerable interest in many industries, but composite coatings of CNTs have not yet been sufficiently developed for use in biomedical implants. This investigation elucidates the wear and corrosion behavior of electroplated Ni/CNT composite coatings on Ti–6Al–4V alloy in Hanks’ solution. Experimental results indicate that the CNTs in an electroplated Ni/CNT composite coating increase its hardness to 98.5% higher than that of a pure Ni coating. Additionally, an Ni/CNT composite coating can form stable and dense passive film, which significantly improves wear and corrosion in Hanks′ solution.     

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.     

Fretting wear behaviors of nanometer Al2O3 and SiO2 reinforced PEEK composites

The influence of diameter and content of Al₂O₃ particles on the tribological behaviors under fretting wear mode was investigated. The surface of PEEK composite and steel ball were examined by SEM and EDS, to identify the topography of wear scar and analyze the distribution of chemical elements in the friction counterparts, respectively. It can be found that the filling of Al₂O₃ powder improves the fretting wear resistance of PEEK composite. With the increase of Al₂O₃ diameter, the area of wear scar on specimen increases first and decreases afterward. However, the wear of composites increases monotonically with increasing Al₂O₃ content. Although the filling of 10 wt.% and 200 nm PTFE powder in PEEK makes the lowest wear of all specimens, no synergistic effect was found when Al₂O₃ and PTFE were filled into PEEK composite together. For the friction pair of PEEK composite and steel ball, abrasive wear and adhesive wear dominate the fretting wear mechanism during fretting. Thermal effect plays a very important role during fretting; thus the property of temperature resistance for polymer material would affect the wear degree on the surface of wear scar.     

Experimental study of the speed-dependence tribotechnical characteristics of some plasma-sprayed oxide coatings at elevated temperatures

The effect of the sliding speed on friction and wear characteristics of plasma-sprayed ceramic coatings (Al₂O₃-13% TiO₂, ZrO₂-8% Y₂O₃, Al₂O₃-modified) was studied. Plasma-sprayed coatings are not hard and have high layered structure. Abrasion of coatings in the friction pair with steel and bronze counter-bodies occurs through brittle detachment conglomerated regions with low cohesive resistance. The modified coating (Al₂O₃) has the highest wear resistance and the lower coefficient of friction compared to the coatings (Al₂O₃-13% TiO₂, ZrO₂-8% Y₂O₃) in the studied velocity range (0.1–10 mm/s). Laser melting can be used as an efficient way of increasing the tribotechnical properties of plasma-sprayed oxide coatings.     

Preliminary investigation of the tribological characteristics of composite coatings sliding against ultrahigh molecular weight polyethylene

The performance of several composite coatings sliding against ultrahigh molecular weight polyethylene was evaluated in 3 h screening tests. The most promising coatings were then selected to run in 48 h wear tests, both dry and in the presence of distilled water. Composite coatings containing particles of Al₂O₃ and Cu and of 18-8 stainless steel and Al₂O₃ in epoxy matrices exhibited thermal, frictional and surface wear characteristics similar to those seen when 316 stainless steel was run against ultrahigh molecular weight polyethylene.     

不同石墨烯添加量下MoS2基复合涂层的摩擦磨损及耐腐蚀性能

为改善MoS2基固体润滑涂层的摩擦磨损性能和耐蚀性能,制备了不同石墨烯（GE）添加量的MoS2复合涂层,利用HSR-2M摩擦磨损试验机测试了复合涂层的摩擦磨损性能,并分析了其磨损机理,通过极化曲线、交流阻抗谱（EIS）研究了涂层在3.5%NaCl溶液中的电化学腐蚀行为。试验结果表明,0.8-GE/MoS2复合涂层的摩擦磨损和耐腐蚀性能最优,其平均摩擦因数和磨损率分别为0.232和2.379×10-13 m3/(N·m),较未添加石墨烯的MoS2涂层分别降低了49.56%和43%,腐蚀速率（1.96×10-8 A/cm2）较纯MoS2涂层（5.54×10-6 A/cm2）降低了近2个数量级。石墨烯的二维片状结构具有良好的自润滑性能,在涂层中均匀分布时能有效阻隔腐蚀介质的渗透,因此,石墨烯的添加提高了MoS2基复合涂层的摩擦学性能和耐腐蚀性能,石墨烯的最优添加量为0.8%（质量分数）。     

Effect of Al2O3 Particle Size on Electrical Wear Performance of Al2O3/Cu Composites

Al₂O₃/Cu composites (1.0 vol%) reinforced with different size of α-Al₂O₃ particles were fabricated by a powder metallurgy method and electrical sliding wear tests were performed on a self-made pin-on-disk electrical wear tester. The effect of Al₂O₃ particle size on electrical wear performance of the Al₂O₃/Cu composite was studied, and the wear mechanism of the Al₂O₃/Cu composite was also discussed based on worn surface observations. The results show that the tribological properties of A1₂O₃/Cu composite are closely related to the mechanical properties. With an increase in Al₂O₃ particle size, the wear rates of A1₂O₃/Cu composites have a reverse variation with hardness of A1₂O₃/Cu composites. In the range of 50–100 nm, Al₂O₃/Cu composites have the highest wear resistance and mechanical properties. Microstructural observation revealed that the wear mechanisms of Al₂O₃/Cu composites were mainly adhesive wear and plastic deformation accompanied by a small amount of arc damage. In addition, the plastic deformation area on the pin sample of the frictional end depends on the electrical wear resistance of A1₂O₃/Cu composites.     

Wear behavior and mechanisms of alumina-based ceramic tools in machining of ferrous and non-ferrous alloys

In this paper, the machining performance and wear mechanisms of two alumina-based ceramic cutting tools (Al₂O₃/TiB₂ and Al₂O₃/TiB₂/SiC_w) in continuous turning of hardened steel and nickel based alloy (Inconel 718) were examined. Results showed that in turning of hardened steel performed under identical conditions, Al₂O₃/TiB₂/SiC_w tool exhibited lower flank wear resistance than that of Al₂O₃/TiB₂ tool, the mechanisms responsible for this were determined to be the strong atom bonding between SiC and Fe, and the whisker pullout from the matrix for Al₂O₃/TiB₂/SiC_w ceramic tool. In continuous turning of Inconel 718, the Al₂O₃/TiB₂/SiC_w tool showed greatly improved flank wear resistance compared to Al₂O₃/TiB₂ tool, adhesion and abrasion wear were found to be the dominant wear mechanisms, the adhesion and diffusion of Ni, and Cr of Inconel 718 to the tool rake face may accelerate the tool wear rates.     

The compatibility of TiB2 protective coatings with SiC fibre and Ti-6Al-4V

TiB₂ coatings have been studied as prospective protective layers to inhibit the interfacial reaction between SiC fibres and Ti-alloy matrices. This protective coating has been deposited onto SiC monofilament fibres using a chemical vapour deposition (CVD) technique. The fibre-matrix compatibility of these TiB₂-coated SiC fibres in Ti-6Al-4V composites was evaluated by incorporating the coated fibres into Ti-6Al-4V using a diffusion bonding technique. The interfaces of this composite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis, to evaluate the interfacial microstructures, chemical stability and the efficiency of TiB₂ as a protective coating for SiC fibres in Ti-alloy matrices, and to study the effects of deposition temperature on the interface of the coated fibre. Results show that stoichiometric TiB₂ coatings are stable chemically to both SiC fibres and Ti-6Al-4V and hinder the deleterious fibre-matrix reactions effectively. Boron-rich TiB₂ coatings should be avoided, as they lead to the formation of a needle-like TiB phase at the fibre–matrix interface. These findings provide promising evidence for the value of further exploration of the use of stoichiometric TiB₂ as a protective coating for SiC fibre in Ti-based composites.     

Tribological properties and studies in SBF of Ta2O5/TiN/TiO2 monolayer and bilayer coatings on biomedical Ti6Al4V alloy

In this study, Ta₂O₅, TiN, and TiO₂ are coated with magnetron sputtering method as monolayer and bilayer on Ti6Al4V alloy used in biomedical applications. The deposited coatings are characterized, and their mechanical properties are determined by nanoindentation tests. As a result of the pin-on disc wear test performed in dry environment and room temperature, in vitro corrosion test was applied to the samples with high wear resistance, and the information about the tribological properties was obtained. Experimental results show that the existence of the intermediate layer has also significant effect on the corrosion resistance of the coatings. The biocompatibility of the Ta₂O₅/TiO₂ coating was examined by keeping it in simulated body fluid (SBF) due to its noticeable wear and corrosion resistance properties, the growth of apatite, which is described as an indicator of biocompatibility, occurred on the sample surface after 7 day.

     

Effects of Surface Pretreatment of Ti-6AI-4V on the Adhesion and Wear Lifetimes of Sputtered MoS2 Coatings

Improving the adhesion and wear endurance lifetimes of the solid lubricant molybdenum disulfide (MoS₂) on titanium (Ti) alloys was studied in this experimental investigation. Ti-6Al-4V alloy specimens were implanted with gas ions or coated with ceramic layers prior to coating with sputtered MoS₂ to investigate the adhesion and wear lifetimes of the MoS₂ coatings. The greatest improvement in scratch adhesion (2.4 times Ti-6Al-4V coated directly with MoS₂) was observed for an MoS₂/diamond-like carbon/Si multilayer coating. Sliding wear tests revealed the greatest lifetime improvement (3.2 ×) was for an MoS₂/TiC dual-layer coating. Increased MoS₂ adhesion was observed for pretreated surfaces with a Vickers microhardness greater than 800 kgf/mm². Increased adhesion of MoS₂ for bond layers with lower elastic moduli (estimated) is suggested. Therefore the ratio hardness/elastic modulus may be a potential figure of merit for surface pretreatment selection.