单层CBN砂轮内喷固体润滑剂的磨削试验研究

本文采用冷却介质内喷固体润滑剂的方法,选取固体润滑剂(石墨)代替冷却液,实现绿色磨削加工。设计并制作了内喷固体润滑剂的试验装置冷却介质输送系统,选用石墨作为试验用固体润滑剂且组装了润滑剂供粉系统,并对其性能及流动性进行初步分析和调试,从而实现后期试验的最佳调配,完成可控润滑剂内喷单层CBN砂轮磨削钛合金的试验。结果表明,固体润滑剂内喷砂轮能够降低磨削工件表面温度。     

基于 DEFORM－3D 的固体润滑涂层对磨削温度场的影响仿真研究

针对磨削过程中产生的大量磨削热容易导致磨削灼伤的问题,进行了固体润滑涂层对磨削温度场影响的仿真研究。基于DEFORM－3D有限元仿真软件,模拟了电镀CBN砂轮高速磨削TC4钛合金的过程,比较了电镀CBN砂轮在有无固体润滑软涂层的条件下高速磨削TC4钛合金时温度场的变化规律。研究结果表明,固体润滑涂层应用于高速磨削中,可有效降低磨削温度,避免磨削灼伤。     

CBN砂轮与SiC砂轮加工钛合金的对比研究

分别对CBN砂轮和SiC砂轮进行了钛合金干磨削试验,研究了在相同参数下,磨削钛合金表面形貌、粗糙度和磨削力等情况。结果表明:随着磨削深度增加,SiC砂轮磨削后的钛合金表面形貌逐渐恶化,材料堆积增多,严重影响表面粗糙度;在相同实验条件下,CBN砂轮钛合金表面质量明显优于前者,主要原因是CBN砂轮加工时产生磨削力更小,对工件挤压更小,产生热量也更少。     

基于轴向旋转热管砂轮的钛合金成型磨削试验研究

针对钛合金等难加工材料成型磨削时存在的磨削弧区温度高、型面温度分布不均的问题,设计制作了轴向旋转热管成型砂轮。通过开展轴向旋转热管砂轮的钛合金成型磨削试验,探究了热流密度、充液率及砂轮转速各因素下热管砂轮对磨削弧区温度的控制效果,从而得到最佳磨削参数及热管砂轮最佳充液率,并在此条件下进一步开展磨削试验。对磨削后的工件表面质量进行了分析,发现轴向旋转热管砂轮能明显降低弧区温度,减小型面温差,并避免工件烧伤现象,这表明其在强化弧区换热、控制磨削温度上具有较大优势。     

叶轮式内喷润滑剂砂轮的流场分析及实验研究

提出了一种叶轮式内喷润滑砂轮结构及其磨削加工的方法。基于FLUENT软件模拟分析了叶轮式内喷润滑砂轮的内腔固体颗粒流场,设计出了叶轮式内喷润滑砂轮,并通过内喷润滑砂轮磨削TC4钛合金实验,分析了内喷润滑砂轮的磨削加工性能。结果表明：叶轮式固体内喷润滑砂轮中的润滑剂在离心力的作用下,通过砂轮外缘微孔直接析出到砂轮表面,能够实现抑制钛合金黏附、降低磨削区温度和摩擦因数的目的。     

石墨粉末内喷润滑砂轮研制及其实验研究

提出了一种石墨固体润滑剂粉末内喷润滑的砂轮,其主要由砂轮轴、砂轮底盘、基体和叶片叶轮等组成。设计并制作出了单层电镀固体粉末内喷润滑砂轮,采用自制的恒力夹具装置进行了磨削实验研究,采用三维体视显微镜观察了砂轮磨粒的表面形貌,分析了砂轮线速度与工件表面粗糙度的关系。研究结果表明,石墨粉末内喷润滑砂轮在一定转速条件下能形成磨削润滑涂层,改善磨削工件的表面质量。     

低温冷风微量润滑磨削钛合金换热机理与对流换热系数模型

钛合金磨削过程中工件表面热损伤已成为亟需解决的技术难题。微量润滑技术应用于钛合金磨削是实现可持续制造的发展方向,但存在热耗散和润滑减摩能力不足的技术缺陷。利用多能场辅助加工是解决以上技术难题的必然选择,低温冷风取代常温空气携带微量润滑剂,可显著提高磨削区液膜换热和润滑性能。但润滑剂物理特性演变规律及磨削区液膜换热机理等科学问题尚需揭示。基于此,研究了润滑剂低温物理特性演变规律,建立了冷风温度与润滑剂物理参数的量化映射关系。分析了低温冷风微量润滑砂轮工件界面流动液膜换热规律,建立了磨削区流动液膜换热量理论模型。进一步,建立了不同冷风条件下润滑剂对流换热系数模型。进行了流动液膜对流换热系数和低温冷风微量润滑磨削钛合金换热性能验证实验,结果显示,对流换热系数理论值与测量值吻合,冷风温度为-10℃时,误差为8.5%;工件表面温度实验值和理论值变化趋势吻合,磨削深度为30μm、冷风温度为-40℃时,误差为7.7%。研究结果为低温冷风微量润滑磨削钛合金提高工件表面完整性提供技术支持。     

加工钛合金的新型磨具——浸渍涂层砂轮问世

江苏省盐城市砂轮厂根据南京航空学院的科研成果制造的加工钛合金的新型磨具——浸渍涂层砂轮,经航天部贵州一七○厂、成都四二○厂等单位试用,证明是较为理想的钛合金磨具。钛合金是质坚韧而轻的材料。在磨削时,钛屑会迅速粘附到砂轮上,堵塞砂轮气孔,使磨削难以持续进行。浸渍涂层砂轮选用石墨和二硫化铝作为主要渗渍剂,经过浸渍涂层工艺处理,使渗渍剂牢固地粘结在磨粒表层。这样,一方面有效地防止磨粒与钛合金的直接接触,消     

用致冷剂处理干磨砂轮的试验研究

钛合金磨削加工比较困难,特别是干磨尤其如此,针对这一问题,进行了致冷剂的研制。文本对制冷剂的研制及使用、致冷剂处理钛合金干磨用砂轮进行了理论分析与试验研究,并阐述了应用致冷剂降低磨削温度,提高工件表面质量的机理,并通过分析试验得出致冷剂的配方和操作规程,验证了致冷剂的效果使用和技术经济价值。     

金刚石砂轮平面磨削TC4钛合金的表面完整性研究

以TC4钛合金为研究对象,在乳化液条件下采用金刚石砂轮对TC4钛合金进行平面磨削试验,对比分析在不同粒度和磨削用量下的磨削表面粗糙度、显微硬度、表面层微观组织及表面残余应力的变化规律.结果 表明:砂轮线速度和磨削深度对零件表面粗糙度和显微硬度的影响比较显著;磨削深度对表面残余应力的影响最大,工件速度次之;从工件表面层微观组织以及砂轮粒度对工件表面粗糙度的影响看,砂轮粒度号越大,砂轮磨削的工件表面质量越好.金刚石砂轮在乳化液条件下磨削TC4钛合金,磨削工件表面均为残余压应力,有利于提高零件的寿命.     

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°.     

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。     

Determination of the friction factor of Ti-6Al-4V titanium alloy in hot forging by means of ring-compression test using FEM

The friction factor of Ti-6Al-4V titanium alloy under hot forging situation was determined by the combined approach of ring-compression tests and finite element (FE) simulations. It is noticed in particular that the heat-transfer (HT) coefficient has significant effects on the metal flow and calibration curves, thereby affects the measurement of interfacial friction factor. Moreover, the HT coefficients are different for glass lubricant and dry friction conditions. Therefore, different HT coefficients should be employed to generate the calibration curves when both of the lubricant conditions were applied for determining the interfacial friction coefficients in hot ring-compression of Ti-6Al-4V titanium alloy.     

Determination of the friction factor of Ti-6Al-4V titanium alloy in hot forging by means of ring-compression test using FEM

The friction factor of Ti-6Al-4V titanium alloy under hot forging situation was determined by the combined approach of ring-compression tests and finite element (FE) simulations. It is noticed in particular that the heat-transfer (HT) coefficient has significant effects on the metal flow and calibration curves, thereby affects the measurement of interfacial friction factor. Moreover, the HT coefficients are different for glass lubricant and dry friction conditions. Therefore, different HT coefficients should be employed to generate the calibration curves when both of the lubricant conditions were applied for determining the interfacial friction coefficients in hot ring-compression of Ti-6Al-4V titanium alloy.     

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.     

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.     

An investigation on sliding wear behavior of PVD coatings

Ti-6Al-4V alloy rubbing against aluminum-bronze 630 was evaluated in this work. High velocity oxygen fuel (HVOF) WC-10%Co-4%Cr thermal sprayed and TiN, CrN and DLC physical vapor deposition (PVD) coatings were applied to increase titanium substrate wear resistance. Pin-on-disk tests were performed with a normal force of 5 N and at a speed of 0.5 m/s, with a quantitative comparison between the five conditions studied. Results showed higher wear resistance for Ti-6Al-4V alloy DLC coated and aluminum-bronze 630 tribological pair and that the presence of graphite carbon structure acting as solid lubricant was the main wear preventing mechanism.     

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.     

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.     

硬质合金刀具高速车削钛合金的切削性能研究

采用单因素试验法,用未涂层硬质合金刀具和TiAlN涂层硬质合金刀具对Ti-6Al-4V钛合金进行了高速干车削试验,通过对切削过程中切削力、刀具寿命、切削温度以及加工表面粗糙度的分析,得出了两种刀具高速干车削钛合金的切削性能,为钛合金高速切削刀具的设计提供了试验依据。