新型刚玉砂轮磨削GH4169镍基高温合金的性能评价研究

镍基高温合金是航空发动机部件的常用材料,其磨削加工存在工具损耗严重、寿命短等难题。针对3种新研制的刚玉砂轮(分别为粒度60#的微晶和单晶混合磨料砂轮、粒度60#的单晶刚玉砂轮,以及粒度70#的单晶刚玉砂轮),开展了GH4169镍基高温合金材料的磨削试验,从磨削力、磨削温度、砂轮磨损以及表面粗糙度等方面对3种砂轮的磨削性能进行了评价。结果表明,3种砂轮磨削GH4169材料在砂轮磨损和表面粗糙度方面未表现出明显差异,而通过对磨削力和磨削温度的综合评价发现粒度60#的单晶刚玉砂轮的磨削性能更优。3种砂轮磨削GH4169材料的磨削比在0.5~3之间。在正常磨削条件下,3种砂轮的磨削表面粗糙度Ra小于0.4μm。同时发现,砂轮磨损(主要包括磨粒的破碎和脱落)是造成磨削表面缺陷形成的重要原因。     

Research on Ultrasonic Vibration Grinding of the Hard and Brittle Materials

It is well known that grinding techniques are main methods to machine hard and brittle materials such as engineering ceramics. But the conventional grinding has many shortcomings such as poorer surface finish,quicker wear and tear of grinding tools,lower effi-ciency and so on. Ultrasonic vibration grinding (UVG) which combines ultrasonic machining and grinding emerged as a developing and promising technique in recent years. In this paper,experimental studies on UVG were conducted on several kinds of hard and brittle material by altering processing parameters such as vibration frequency and its amplitude,diamond abrasive grit size,cutting depth,feeding speed and rotary speed of tools. The experimental results show that alteration in any of above mentioned parameters will bring effects on the processed surface finish of these materials. Of them,the diamond abrasive grit size has the greatest. Moreover,conven-tional grinding experiments were also carried out on these materials. By comparison,it was found that the UVG is superior to the con-ventional method in terms of the ground surface quality,the working efficiency and the wear rate of tools.     

Grain erosion wear properties and grinding performance of porous aggregated cubic boron nitride abrasive wheels

Cubic boron nitride (cBN) superabrasive grinding wheels exhibit unique advantages in the grinding of difficult-to-cut materials with high strength and toughness, such as titanium alloys and superalloys. However, grinding with multilayered metallic cBN superabrasive wheels faces problems in terms of grain wear resistance, the chip storage capability of the working layers and the stability and controllability of the dressing process. Therefore, in this work, novel metallic cBN superabrasive wheels with aggregated cBN (AcBN) grains and open pore structures were fabricated to improve machining efficiency and surface quality. Prior to the grinding trials, the air-borne abrasive blasting process was conducted and the abrasive blasting parameters were optimized in view of wear properties of cBN grains and metallic matrix materials. Subsequently, the comparative experiments were performed and then the variations in grinding force and force ratio, grinding temperature, tool wear morphology and ground surface quality of the multilayered AcBN grinding wheels were investigated during machining Ti–6Al–4V alloys. In consideration of the variations of grain erosion wear volume and material removal rate per unit of pure metallic matrix materials as the abrasive blasting parameters changes, the optimal abrasive blasting parameters were identified as the SiC abrasive mesh size of 60# and the abrasive blasting distance and time of 60 mm and 15 s, respectively. The as-developed AcBN grains exhibited better fracture toughness and impact resistance than monocrystalline cBN (McBN) grains because of the existence of metal-bonded materials amongst multiple cBN particles that decreased crack propagation inside whole grains. The metallic porous AcBN wheels had lower grinding forces and temperature and better ground surface quality than vitrified McBN wheels due to the constant layer-by-layer exposure of cBN particles in the working layer of AcBN wheels.     

Development of a new high-shear and low-pressure grinding wheel and its grinding characteristics for Inconel718 alloy

Nickel-based alloy has been widely used due to its outstanding mechanical properties. However, Nickel-based alloy is a typical difficult-to-machine material, which is a great constrain for its application in the manufacturing field. To improve the surface quality of the ground workpiece, a new high-shear and low-pressure grinding wheel, with high ratio of tangential grinding force to normal grinding force, was fabricated for the grinding of selective laser melting (SLM) manufactured Inconel718 alloy. The principle of high-shear and low-pressure grinding process was introduced in detail, which was quite different from the conventional grinding process. The fabrication process of the new grinding wheel was illustrated. A serial of experiments with different processing parameters were carried out to investigate the grinding performance of the developed grinding wheel via analyzing surface roughness and surface morphology of the ground workpiece. The optimal processing parameters of high-shear and low-pressure grinding were obtained. The surface roughness of ground workpiece was reduced to 0.232 μm from the initial value of 0.490 μm under the optimal grinding conditions. It was found that the initial scratches on the ground workpiece were almost completely removed after the observations with the metalloscopy and the field-emission scanning electron microscopy (FE-SEM). The capability of the newly developed high-shear and low-pressure grinding wheel was validated.     

Grinding performance evaluation of porous composite-bonded CBN wheels for Inconel 718

For high-efficiency grinding of difficult-to-cut materials such as titanium and nickel alloys, a high porosity is expected and also a sufficient mechanical strength to satisfy the function.However, the porosity increase is a disadvantage to the mechanical strength. As a promising pore forming agent, alumina bubbles are firstly induced into the abrasive layer to fabricate porous cubic boron nitride（CBN） wheels. When the wheel porosity reaches 45%, the bending strength is still high up to 50 MPa with modified orderly pore distribution. A porous CBN wheel was fabricated with a total porosity around 30%. The grinding performance of the porous composite-bonded CBN wheel was evaluated in terms of specific force, specific grinding energy, and grinding temperature, which were better than those of the vitrified one under the same grinding conditions. Compared to the vitrified CBN wheel, clear straight cutting grooves and less chip adhesion are observed on the ground surface and there is also no extensive loading on the wheel surface after grinding.     

激光宏观结构化金刚石砂轮磨削氧化铝工艺

为了研究砂轮表面结构化对砂轮磨削性能的影响,利用脉冲激光对树脂结合剂金刚石砂轮进行了表面宏观结构化。采用6种不同类型的金刚石砂轮表面宏观结构进行了氧化铝的磨削实验,建立了激光宏观结构化金刚石砂轮的磨削力模型,比较了6种不同激光宏观结构化金刚石砂轮与非结构化砂轮在不同磨削参数下磨削力的差异,分析了砂轮制造后的表面形貌与结构化砂轮的磨损特性。实验结果表明,砂轮宏观结构化对磨削性能有很大影响,激光宏观结构化砂轮的磨削力可以减小2. 5%~24. 5%,砂轮结构化后的表面形貌出现石墨化现象;宏观结构化砂轮沟槽边缘磨损加剧,但沟槽磨损并没有明显加快宏观结构化砂轮的磨损。     

航空发动机钛材料磨削技术研究现状及展望

钛材料主要指钛合金、钛铝金属间化合物和钛基复合材料，具有密度低、强度高、抗氧化与蠕变性能好等优异特性，在航空发动机领域具有广泛应用前景。钛材料属于典型的难加工材料。磨削是高效精密加工钛材料的重要方法，可以获得良好的加工精度和表面质量。首先概述了钛材料在航空发动机中的应用及其磨削工艺技术总体情况。随后，从磨削力与磨削温度、砂轮磨损、材料去除机理、表面完整性等方面阐述了钛材料磨削技术的研究进展，并总结了针对钛材料磨削关键问题提出的新工艺和新方法。最后，对钛材料磨削技术未来的研究方向进行了展望。     

原位自生TiB_2/Al复合材料磨削表面质量研究

原位自生TiB_2/Al复合材料具有密度小,比强度高,比模量大等特点,在航空航天领域具有广泛的应用前景。为探索原位自生TiB_2/Al复合材料的磨削加工性能,选用单晶刚玉SA砂轮、白刚玉WA砂轮和CBN砂轮在不同磨削参数下对TiB_2/Al复合材料进行磨削试验。首先研究了砂轮材质、转速、工件速度、磨削深度对工件表面粗糙度的影响规律;其次通过对工件表面形貌、磨屑形态、砂轮磨损的观测分析,探索了原位自生TiB_2/Al复合材料磨削表面成形机制;最后基于试验数据,给出了TiB_2/Al复合材料磨削工艺参数优选域。本研究可为颗粒增强金属基复合材料磨削加工提供基础理论支撑。     

Investigation on induction brazing of profiled cBN wheel for grinding of Ti-6Al-4V

Profiled monolayer cBN wheel was induction brazed for grinding of titanium dovetail slot in this study. Aimed at acquiring a uniform temperature distribution along the profiled surface and reducing the thermal deformation of the brazed wheel, a finite element model was established to investigate the temperature uniformity during induction brazing. A suitable induction coil and the related working parameters were designed and chosen based on the simulation results. Ag-Cu-Ti alloy and cBN grains were applied in the induction brazing experiment. The results showed geometric deformation of the brazed wheel was no more than 0.01 mm and chemical reaction layer were found on the brazed joint interface. Further validation tests were carried out by grinding of Ti-6Al-4V alloy. Compared to the electroplated wheel, the brazed wheel showed better performance such as low specific grinding energy and good ground quality in grinding of Ti-6Al-4V alloy. Abrasion wear was found to be the main failure mode for the induction brazed wheel, while adhesion and grains pull-out were the main failure mode for the electroplated wheel.     

Feasibility study of creep feed grinding of 300M steel with zirconium corundum wheel

The ultrahigh strength 300M steel has been commonly used in the manufacture of aircraft landing gear and rotor shaft parts due to its excellent mechanical properties. Creep feed grinding is one of the essential operations during the whole component manufacturing processes. In this work, the feasibility of creep feed grinding of 300M steel by using the hard zirconium corundum wheel was theoretically and experimentally evaluated. A variety of responses including grinding forces, temperature fields...     

渐开线碟形砂轮磨削面齿轮数控加工研究

为进行面齿轮数控精密加工,提出了一种渐开线碟形砂轮磨削面齿轮加工方法.根据面齿轮成形过程及磨削加工原理,推导了渐开线碟形砂轮磨削面齿轮齿面方程,进行了面齿轮磨削加工机床设计,给出了基于机床结构的面齿轮磨削加工方法,进行了磨削加工过程中的啮合点刀位计算;借助VERICUT软件进行了面齿轮数控磨削加工仿真,最后进行了面齿轮磨削加工试验,通过对面齿轮齿面进行检测,得到齿面偏差最大值为-10.1~12.1μm,结果验证了渐开线碟形砂轮磨削加工面齿轮方法的正确性.      

磨粒磨损对砂带磨削TC17表面完整性的影响研究

砂带磨粒磨损直接影响磨削表面质量进而影响构件综合服役性能.以表面完整性为评估指标,对砂带磨损前后钛合金的表面加工质量进行了试验研究,揭示了砂带磨粒磨损对磨削TC17表面粗糙度、残余应力和表面硬度的影响规律及机制.结果表明,磨粒磨损后由于高度均匀化、单位面积切削磨粒数增加、磨削深度减小,使得表面粗糙度减小、纹理均匀细腻,...     

TC4-DT钛合金磨削表面特性及其摩擦磨损性能

钛合金是一种典型难磨削加工材料,磨削表面易出现烧伤、裂纹等热损伤。本文开展了TC4-DT钛合金磨削实验,通过扫描电镜（SEM）、能谱（EDS）、X射线衍射（XRD）、显微硬度仪、金相显微镜及球-盘摩擦磨损实验仪研究了其表面特性及摩擦磨损性能。结果表明：低速磨削表面质量好,摩擦磨损性能较基体略提高;当砂轮线速度为80 m/s时,磨削表面质量良好,摩擦系数为0.38,较基体降低40%;而砂轮线速度为100 m/s时,磨削表面出现严重烧伤、网状裂纹。因此选择合理的高速磨削工艺可避免烧伤、裂纹等热损伤缺陷,并可有效改善表面摩擦磨损性能;磨削表面干摩擦磨损机制为磨粒磨损、粘着磨损和剥层磨损。     

Tool Life and Surface Integrity in High-speed Milling of Titanium Alloy TA15 with PCD/PCBN Tools

Titanium alloys are widely used in aeronautics that demand a good combination of high strength, good corrosion resistance and low mass. The mechanical properties lead to challenges in machining operations such as high process temperature as well as rapidly increasing tool wear. The conventional tool materials are not able to maintain their hardness and other mechanical properties at higher cutting temperatures encountered in high speed machining. In this work, the new material tools, which are polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) tools, are used in high-speed milling of Ti-6.5Al-2Zr-1Mo-1V (TA15) alloy. The performance and wear mechanism of the tools are investigated. Compared to PCBN tool, PCD tool has a much longer tool life, especially at higher cutting speeds. Analyses based on the SEM and EDX suggest that attrition, adhesion and diffusion are the main wear mechanisms of PCD and PCBN tools in high-speed milling of TA15. Oxidation wear is also observed at PCBN tool/workpiece interface. Roughness, defects, micro-hardness and microstructure of the machined surface are investigated. The recorded surface roughness values with PCD/PCBN tools are bellow 0.3 μm at initial and steady cutting stage. Micro-hardness analysis shows that the machined surface hardening depth with PCD and PCBN tools is small. There is no evidence of sub-surface defects with PCD and PCBN tools. It is concluded that for TA15 alloy, high-speed milling can be carried out with PCD/PCBN tools.     

Grindability and Surface Integrity of Cast Nickel-based Superalloy in Creep Feed Grinding with Brazed CBN Abrasive Wheels

The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This article studies experimentally the effects of process parameters (i.e. wheel speed, workpiece speed and depth of cut) on the grindability and surface integrity of cast nickel-based superalloys, i.e. K424, during creep feed grinding with brazed cubic boron nitride (CBN) abrasive wheels. Some important factors, such as grinding force and temperature, specific grinding energy, size stability, surface topography, microhardness and microstructure alteration of the sub-surface, residual stresses, are investigated in detail. The results show that during creep feed grinding with brazed CBN wheels, low grinding temperature at about 100 °C is obtained though the specific grinding energy of nickel-based superalloys is high up to 200-300 J/mm³. A combination of wheel speed 22.5 m/s, workpiece speed 0.1 m/min, depth of cut 0.2 mm accomplishes the straight grooves with the expected dimensional accuracy. Moreover, the compressive residual stresses are formed in the burn-free and crack-free ground surface.     

镍基高温合金GH4169磨削参数对表面完整性影响

研究了用单晶刚玉砂轮磨削镍基高温合金GH4169时,磨削参数对表面完整性中的表面特征(表面粗糙度、表面形貌、表面显微硬度和表面残余应力)的影响,以期优化磨削参数.砂轮速度依次选择15,20,25m/s,磨削深度分别选择50,100,150μm,工件速度分别选择5,10,15m/min.研究结果表明:表面粗糙度对工件速度的变化最敏感,表面显微硬度对砂轮速度变化最敏感,表面残余应力对砂轮速度变化最敏感;同时表明了磨削参数对磨削表面形貌、显微硬度梯度、微观组织、残余应力梯度的影响,揭示了表面完整性中的变质层形成规律.其塑性变形层在5～10μm,显微硬度变化影响层为80～100μm,残余应力影响层厚度为80～200μm,其为磨削镍基高温合金表面完整性控制研究提供相关的实验数据基础.      

Performance evaluation of creep feed grinding of γ-TiAl intermetallics with electroplated diamond wheels

This paper evaluates the performance of creep feed grinding γ-TiAl intermetallic (Ti-45Al-2Mn-2Nb) using electroplated diamond wheels. Firstly, a comparative analysis with the grinding results by using electroplated CBN wheels was conducted, mainly involving abrasive wheel wear behavior and maximum material removal rate below surface burn limit. It was found that the diamond wheel would produce much better grinding results including lower wheel wear rate and higher maximum material removal rate. Then the surface integrity obtained at different level of material removal rate was characterized with the utilization of the diamond wheel. The poor ductility of this γ-TiAl intermetallic material was found to have a marginal effect on the surface integrity, as no severe surface defects such as material pullout were generated during the stable wheel wear stage. For the involved operating parameters, a deformation layer was produced with ∼10 μm or more in thickness depending on the material removal rate used. Meanwhile, a work-hardened layer extending to more than 100 μm was produced with a maximum microhardness of above 520 HV_0.05 (bulk value 360 HV_0.05). The residual stress remained compressive, with a value of above −100 MPa and even up to −500 MPa for an elevated material removal rate. Shearing chip was the main chip type, indicating good wheel sharpness in the grinding process.     

Fretting wear behaviour of machined layer of nickel-based superalloy produced by creep-feed profile grinding

Fretting wear has an adverse impact on the fatigue life of turbine blade roots. The current work is to comparatively investigate the fretting wear behaviour of the nickel-based superalloy surfaces produced by polishing and creep-feed profile grinding, respectively, in terms of surface/subsurface fretting damage, the friction coefficient, wear volume and wear rate. Experimental results show that the granulated tribolayer aggravates the workpiece wear, while the flat compacted tribolayer enhances the wear resistance ability of workpiece, irrespective of whether the workpiece is processed by polishing or grinding. However, the wear behaviors of tribolayers are different. For the polished surface, when the normal load exceeds 100 N, the main defects are crack, rupture, delamination and peeling of workpiece materials; the wear mechanism changes from severe oxidative wear to fatigue wear and abrasive wear when the loads increase from 50 to 180 N. As for the ground surface, the main wear mechanism is abrasive wear. Particularly, the ground surface possesses better wear-resistant ability than the polished surface because the former has the lower values in coefficient friction (0.23), wear volume (0.06 × 10⁶ μm³) and wear rate (0.25 × 10^?16 Pa^?1). Finally, an illustration is given to characterize the evolution of wear debris on such nickel-based superalloy on the ground surface.     

钛合金风扇叶片磨抛加工性能试验研究

针对钛合金风扇叶片磨抛加工中砂轮易磨损、工件表面易烧伤的问题,开展了钛合金材料磨抛加工性试验研究,主要考察砂轮选型、磨抛工艺参数等关键因素对钛合金材料磨抛加工性的影响,并对试验结果进行了分析研究。试验结果表明,在保证工件表面加工质量(R_a0.8μm,表面无烧伤)的前提下,普通磨料砂轮GC46L10V磨抛加工钛合金的材料去除率和磨抛比分别可达5000mm~3/min和2.5,超硬磨料陶瓷结合剂CBN砂轮磨抛加工钛合金的材料去除率和磨抛比分别可达2000mm~3/min和4。基于研究结果,针对钛合金风扇叶片开展了砂带磨抛加工验证试验,工件加工质量良好。     

磁流变弹性体砂轮抛光镍基高温合金表面完整性研究

为了改善磨削后镍基高温合金GH4169的表面完整性,本文采用磁流变弹性体砂轮对镍基高温合金GH4169进行抛光试验研究。首先,通过模压成型的方法制备了磁流变弹性体砂轮,并对其表面微观形貌及不同磁场强度下的硬度进行了表征。其次将制备出的磁流变弹性体砂轮用于对镍基高温合金GH4169的抛光工艺试验中,并讨论抛光工艺参数中磁场强度对镍基高温合金表面完整性的影响。试验结果表明：在一定的磁场强度范围内,零件抛光后的表面粗糙度和显微硬度随着磁场强度的增大而减小,同时增大磁场强度也有利于改善零件的表面形貌,减少砂轮的磨损量,降低零件磨削后的亚表面损伤层厚度。