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.     

Superplastic-like forming of Ti-6Al-4V alloy

Superplastic forming of titanium alloys is used for producing structural components, since it is an effective way to manufacture complex-shaped parts in a one-step operation. An optimized sheet-forming process has been designed incorporating a non-isothermal heating system to establish a fast forming process. This work sought to expand the advantages of the technology to the forming of Ti-6Al-4V alloy at 800 °C and shorter cycle time. The minimum thicknesses area was found at the outward corners, showing a maximum percent thinning of 54 %. In addition to stress variations, the cracks resulting from hot drawing and the oxidation on the sheet surface are the other reasons leading to thickness reduction. From the oxidization behavior of Ti-6Al-4V alloy, it was revealed that the decrease in forming temperature from 900 to 800 °C significantly reduced the formation rate of oxide film on the sheet surface. The study also showed that the main microstructure evolution of Ti-6Al-4V alloy under these conditions was recrystallization.     

Ti-6Al-4V钛合金板与304L不锈钢网的扩散焊

分别在800℃、825℃、850℃焊接温度、30 m in保温时间,3 MPa焊接压力下,进行Ti-6A l-4V钛合金板与304L不锈钢网的真空扩散焊接。对接头组织结构与化学元素扩散进行了扫描电镜与能谱分析,并测试了接头的剪切强度。结果表明:不添加中间过渡层金属,可以成功地实现钛合金板与不锈钢网的扩散焊接,并使接头的剪切强度达到90 MPa以上。不锈钢网中的Fe、N、iCr扩散并固溶到钛合金中,稳定了β相,使钛合金在一定深度上,其组织由原来的α+β双相结构转变为单相的β相。不锈钢中的Cr,由于钛合金中Ti的扩散进入,而在界面发生了上坡扩散现象。这种Cr在不锈钢一定深度内的富集,形成窄长的富Cr区域,冷却后转变为硬脆的σ相。但在焊接接头中没有发现明显其它的金属间化合物或氧化物相的生成,使得接头的机械性能得到了很好的保证。     

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。     

Electric hot incremental forming of Ti-6Al-4V titanium sheet

Electric hot incremental forming of metal sheet is a new technique that is feasible and easy to control to form hard-to-form sheet metals. In the present study, Ti-6Al-4V titanium sheet was studied because it was wildly used in the aeronautics and astronautics industries. Although Ti-6Al-4V titanium can be well-formed in high temperature, the surface quality is a problem. In order to enhance the surface quality, it is very important to select the proper lubricant. At the same time, because Ti-6Al-4V titanium has a lively chemical property, it is very important to choose a processing temperature range in order to acquire excellent plastic property and to prevent oxidation. Various lubricants were selected in processing to compare the effect, and some workpieces were formed at different temperatures to find the best forming temperature. The results show that using the lubricant film of nickel matrix with MoS₂ self-lubricating material, Ti-6Al-4V titanium workpiece was formed with high surface quality, and the optimum thickness of composite coating is 20 μm for Ti-6Al-4V titanium sheet of 1.0-mm thickness. In fact, the lubricant film also does help to prevent oxidation of Ti-6Al-4V titanium sheet. The appropriate temperature range of Ti-6Al-4V forming with slightly oxidized is 500–600°C in processing, and the maximum draw angle formed in this range was 72°.     

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.     

Experimental investigations on effects of tool flank wear on surface integrity during orthogonal dry cutting of Ti-6Al-4V

Machining titanium alloy Ti-6Al-4V is a challenging task since tool flank wear adversely affects surface integrity. Quantitative effects of predetermined tool flank wear values (VB) on the surface integrity were investigated through the orthogonal dry cutting of Ti-6Al-4V. Experimental results indicated that three-dimensional (3D) average surface roughness increased with the VB ranging from 0 to 0.2 mm but decreased at VB = 0.3 mm. Given the effects of rubbing and ironing enhanced, surface material burning and plastic flows emerged on the machined surface at VB = 0.3 mm. Not only the plastic deformation layer became deeper but also the grains were greatly distorted with the increase of tool flank wear. When machined by using the tool at VB = 0.3 mm, the β phase of Ti-6Al-4V decreased near the machined surface layer than that of using the fresh tool. Besides, the depth of work-harden layer increased from 20 to 60 μm with the VB increasing from 0 to 0.3 mm. The softened layer was generated near the machined surface by using the tool at VB = 0.3 mm. In addition, the residual compressive stresses of the machined surface had the trend of decreasing. Experimental results indicated that the VB less than 0.2 mm was the most suitable condition for better surface integrity during orthogonal dry cutting of Ti-6Al-4V. This study aims at providing experimental data for optimizing the processing parameters and improving the surface integrity of Ti-6Al-4V.     

Investigations on corrosion resistance behavior in micro-milling of Ti-6Al-4V and Ti-6Al-7Nb alloy: a comparative study

Journal of Mechanical Science and Technology - We compared the corrosion resistance behavior of Ti-6Al-4V and Ti-6Al-7Nb alloy in micro-milling operation. The influence of parameters such as...     

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.     

砂带干式磨削Ti-6Al-4V钛合金的磨削力

对砂带干式磨削Ti-6Al-4V钛合金的的磨削力进行了测试,分析了磨削参数对磨削力的影响;用动态测力仪、三维体式显微镜、粗糙度仪和显微硬度计对磨削试样表面质量进行了分析,提出了砂带磨削工艺参数的优化方案。结果表明:在砂带干式磨削条件下,磨削力随着磨削深度和工作台进给速度的增大而增加,随着砂带线速度的提高而减小;在砂带线速度为15 m.s-1,工作台进给速度为315 mm.min-1,磨削深度为0.025~0.1 mm时,合金表面粗糙度Ra≤0.35μm。     

Microstructure and performance of multi-dimensional WC-CoCr coating sprayed by HVOF

WC-based coatings deposited by high velocity oxy-fuel (HVOF) spraying have been widely used in many industrial fields, where mechanical components are subjected to severe abrasive wear. Much attention has been especially paid to nanostructured and multimodal WC-based coatings due to their excellent abrasive wear resistance. In this study, a new kind of multi-dimensional WC-10Co4Cr coating, composed of nano, submicron, micron WC particles and CoCr alloy, was developed by HVOF. The microstructure, porosity, microhardness, fracture toughness, and electrochemical properties of the coating were investigated in comparison with nanostructured WC-10Co4Cr coating deposited by HVOF. Abrasive wear resistance of both WC-10Co4Cr coatings was evaluated on wet sand rubber wheel abrasion tester. The results show that the multi-dimensional coating possesses low porosity (0.31 ± 0.09%), excellent microhardness (1126 ± 115 HV_0.3), fracture toughness (4.66 ± 0.51 MPa m^1/2), and outstanding electrochemical properties. Moreover, the multi-dimensional coating demonstrates approximately 36% wet abrasive resistance enhancement than the nanostructured coating. The superior abrasive wear resistance originates from the coating’s multi-dimensional structure and excellent mechanical and electrochemical properties.     

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.     

Friction and wear of titanium alloys sliding against metal, polymer, and ceramic counterfaces

Recent advances in lower-cost processing of titanium, coupled with its potential use as a light weight material in engines and brakes has renewed interest in the tribological behavior of titanium alloys. To help establish a baseline for further studies on the tribology of titanium against various classes of counterface materials, pin-on-disk sliding friction and wear experiments were conducted on two different titanium alloys (Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo). Disks of these alloys were slid against fixed bearing balls composed of 440C stainless steel, silicon nitride, alumina, and polytetrafluoroethylene (PTFE) at two speeds: 0.3 and 1.0 m/s. The friction coefficient and wear rate were lower at the higher sliding speed. Ceramic sliders suffered unexpectedly higher wear than the steel slider. The wear rates, ranked from the highest to the lowest, were alumina, silicon nitride, and steel, respectively. This trend is inversely related to their hardness, but corresponds to their relative fracture toughness. Comparative tests on a Type 304 stainless steel disk supported the fracture toughness dependency. Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses confirmed the tendency of Ti alloys to transfer material to their counterfaces and suggested possible tribochemical reactions between the ceramic sliders and Ti alloy disks. These reaction products, which adhere to the ceramic sliders, may degrade the mechanical properties of the contact areas and result in high wear. The tribochemical reactions along with the fracture toughness dependency helped explain the high wear on the ceramic sliders.     

基于变弹性模量的Ti-6Al-4V板材五点弯曲回弹预测

Ti-6Al-4V钛合金材料在弯曲成形过程中会产生较大的回弹,其弹性模量对回弹影响较大,但以往研究均未考虑材料塑性应变变化过程中弹性模量的变化。以Ti-6Al-4V钛合金为对象,进行了材料的单轴拉伸实验和循环加载-卸载实验,以揭示材料各向异性参数及材料弹性模量随塑性应变变化的规律,在此基础上建立了Ti-6Al-4V钛合金变弹性模量数学模型。基于YLD2000-2D屈服准则及变弹性模量和Mises各向同性两种不同的本构模型,对常温下Ti-6Al-4V钛合金板材的五点弯曲过程进行了数值模拟,为了验证数值模拟结果,进行了常温下Ti-6Al-4V板材的五点弯曲实验,结果显示,前者显著提高了Ti-6Al-4V钛合金弯曲回弹预测精度,预测精度相比后者提高了31.18%。     

喷丸对TC4钛合金材料叶片的影响研究

文章主要通过试验的方式,研究喷丸对钛合金材料(Ti-6Al-4V)长叶片的疲劳寿命、表面粗糙度、表面完整性、渗入Fe元素含量等的影响,为确定合理的钛合金材料长叶片喷丸方式提供一定的帮助。     

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.     

表面机械研磨处理后Zr-4合金的组织与性能

利用表面机械研磨处理(SMAT)技术对Zr-4合金进行了表面纳米化处理,用XRD、光学显微镜、表面粗糙度仪对经SMAT不同时间合金表层的物相组成、平均晶粒尺寸、显微组织和表面粗糙度进行了分析,并使用硬度计测试了距表面不同深度处的硬度.结果表明:经SMAT后Zr-4合金表层的物相组成未改变;SMAT 15 min后Zr-4合金表层平均晶粒尺寸达到最小约为20 nm;SMAT后合金表层出现了一定厚度的塑性变形层;SMAT 60 min后合金表层的硬度约为基体硬度的1.3倍,且沿着深度方向逐渐减小;合金表面粗糙度随SMAT时间的延长先增大后减小最后趋于平稳.     

Fibre laser welding of dissimilar alloys of Ti-6Al-4V and Inconel 718 for aerospace applications

Challenges in dissimilar materials welding are the differences of physical and chemical properties between welding materials and the formation of intermetallic brittle phases resulting in the degradation of mechanical properties of welds. However, dissimilar materials welding is increasingly demanded from the industry as it can effectively reduce material costs and improve the design. In aerospace applications, Ti-6Al-4V titanium alloy and Inconel 718 nickel alloy have been widely used because of their superior corrosion resistance and mechanical properties. In this study, a single-mode continuous-wave fibre laser was used in butt welding of Ti-6Al-4V to Inconel 718. Investigations including metallurgical and mechanical examinations were carried out by means of varying processing parameters, such as laser power, welding speed and the laser beam offset position from the interface of the metals. Simple analytical modelling analysis was undertaken to explain the phenomena that occurred in this process. Results showed that the formation of intermetallic brittle phases and welding defects could be effectively restricted at welding conditions produced by the combination of higher laser power, higher welding speed and shifting the laser beam from the interface to the Inconel 718 alloy side. The amount of heat input and position of laser beam to improve the Ti-6Al-4V/Inconel 718 weld quality are suggested.     

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.     

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.