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...     

Review on monolayer CBN superabrasive wheels for grinding metallic materials

A state-of-the-art review on monolayer electroplated and brazed cubic boron nitride (CBN) superabrasive wheels for grinding metallic materials has been provided in this article. The fabrication techniques and mechanisms of the monolayer CBN wheels are discussed. Grain distri-bution, wheel dressing, wear behavior, and wheel performance are analyzed in detail. Sample appli-cations of monolayer CBN wheel for grinding steels, titanium alloys, and nickel-based superalloys are also provided. Finally, this article highlights opportunities for further investigation of mono-layer CBN grinding wheels.     

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。     

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.     

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,...     

单颗磨粒磨削仿真研究进展

概述了传统磨削仿真的基本方法及发展过程,总结了磨粒模型和工件模型的研究现状,具体分析了有限元法、光滑流体粒子动力学法、分子动力学法以及综合仿真方法等应用于单颗磨粒磨削材料的去除机理、成屑机理、工件表面质量以及磨粒磨损等仿真中的研究现状,最后阐述了各类仿真方法的局限性,并提出了单颗磨粒磨削仿真进一步的发展前景。     

Prediction on grinding force during grinding powder metallurgy nickel-based superalloy FGH96 with electroplated CBN abrasive wheel

In this article, a grinding force model, which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism of grinding force, was established. Three key factors have been taken into accounts in this model, such as the contact friction force between abrasive grains and materials, the plastic deformation of material in the process of abrasive plowing, and the shear strain effect of material during the process of cutting chips formation. The model was finally validated by the orthogonal grinding experiment of powder metallurgy nickel-based superalloy FGH96 by using the electroplated CBN abrasive wheel. Grinding force values of prediction and experiment were in good consistency. The errors of tangential grinding force and normal grinding force were 9.8% and 13.6%, respectively. The contributions of sliding force, plowing force and chip formation force were also analyzed. In addition, the tangential forces of sliding, plowing and chip formation are 14%, 19% and 11% of the normal forces on average, respectively. The pro-posed grinding force model is not only in favor of optimizing the grinding parameters and improving grinding efficiency, but also contributes to study some other grinding subjects (e.g. abrasive wheel wear, grinding heat, residual stress).     

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.     

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.     

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.     

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。     

航空煤油泵轴尾机械密封副材料特性

为选择适合在航空煤油介质中工作的机械密封副材料,对材料的摩擦特性进行了研究,利用摩擦磨损试验机得到不同工况条件与表面粗糙度下材料的摩擦因数、温升,在原子力显微镜(AFM)下对3组典型配对材料的微观磨损形貌进行观测,分析磨粒磨损和黏着磨损的行为差异,计算磨损的关键参数。研究发现:聚四氟乙烯（PTFE)在既定条件下为性能最佳的软材料;硬材料表面粗糙度值为0.05时的摩擦性能最佳,不同硬材料间性能差异不大。研究发现PTFE在配磨材料上产生的犁沟效应最轻微,黏附的元素颗粒最少;黏着磨损会造成表面高度分布函数的偏移,利用离散化求解公式得到了黏着体积与平均黏着厚度。      

Simulation and experimental investigation of inner-jet electrochemical grinding of GH4169 alloy

GH4169 alloy is one of the most commonly used materials in aero engine turbine blades, but its machinability is poor because of its excellent strength at high temperatures. Electrochemical machining (ECM) has become a common method for machining this alloy and other difficult-to-machine materials. Electrochemical grinding (ECG) is a hybrid process combining ECM and conventional grinding. In this paper, investigations conducted on inner-jet ECG of GH4169 alloy are described. Two types of inner-jet ECG grinding wheels were used to machine a flat bottom surface. The machining process was simulated using COMSOL software, and machining gaps under different machining parameters were obtained. In addition, maximum feed rates and maximum material removal rates under different machining parameters were studied experimentally. The maximum sizes and the uniformity of the distributions of the gaps machined by the two grinding wheels were compared. The effects of different applied voltages on the machining results were also investigated.     

Grinding force and surface quality in creep feed profile grinding of turbine blade root of nickel-based superalloy with microcrystalline alumina abrasive wheels

Creep feed profile grinding of the fir-tree blade root forms of single crystal nickel-based superalloy was conducted using microcrystalline alumina abrasive wheels in the present study. The grinding force and the surface quality in terms of surface topography, subsurface microstructure, microhardness and residual stress obtained under different grinding conditions were evaluated comparatively. Experimental results indicated that the grinding force was influenced significantly by the competing predominance between the grinding parameters and the cross-sectional root workpiece profile. In addition, the root workpiece surface, including the root peak and valley regions, was produced with the large difference in surface quality due to the nonuniform grinding loads along the root workpiece profile in normal section. Detailed results showed that the surface roughness, subsurface plastic deformation and work hardening level of the root valley region were higher by up to 25%, 20% and 7% in average than those obtained in the root peak region, respectively, in the current investigation. Finally, the superior parameters were recommended in the creep feed profile grinding of the fir-tree blade root forms. This study is helpful to provide industry guidance to optimize the machining process for the high-valued parts with complicated profiles.     

单颗磨粒磨削实验及其数值模拟的研究进展

单颗磨粒磨削是研究复杂磨削机理的重要手段,本文从单颗磨粒磨削过程和磨粒形状的角度阐述了磨削基础理论;概述了国内外学者以实验研究单颗磨粒的材料去除、切削力行为;基于数值模拟,探讨了不同工艺参数对单颗磨粒磨削力、磨削温度、工件表面质量的影响规律。最后就这一方向的深入研究工作做了展望。     

面向表面粗糙度的砂布轮抛光工艺参数区间优化

针对砂布轮抛光表面粗糙度工艺控制,提出了工艺参数稳定域和优选区间的概念;通过砂布轮抛光TC11叶片试件的正交试验,建立了表面粗糙度对工艺参数灵敏度的数学模型,分析了工艺参数区间敏感性,获得了工艺参数的稳定域和非稳定域;根据工艺参数对表面粗糙度影响趋势图,得到了工艺参数的优选区间;通过航空发动机叶片抛光试验证明工艺参数优选区间是可靠的,为砂布轮叶片抛光工艺以及进行表面粗糙度控制研究提供理论方法和试验依据。     

陶瓷喷涂层精密镜面磨削技术的实验研究

引入金属基超硬磨料砂轮在线电解修整(ELID)技术，对陶瓷喷涂层进行精密镜面磨削的实验研究。结果表明，该技术加工精度高、表面质量好，极具应用前景。     

磨粒建模方法与切削过程仿真研究

针对砂轮表面上磨粒形状不规则、尺寸不确定的几何特征,研究了模拟实际磨粒的几何建模方法。采用随机空间平面切分正六面体的方法构建了具有实际磨粒几何特征的不规则多面体结构磨粒。基于LS-DYNA软件,采用流固耦合有限元法模拟了不规则多面体结构磨粒的切削过程。分析切削过程中工件材料的应力分布规律与切削变形规律,得出结论:工件材料的加工应力主要集中在与磨粒切削刃及棱角接触的区域;切屑沿磨粒挤压前面向上流动,并于挤压面法向方向上流出;磨粒挤压前角的增大有利于切屑的形成。利用陶瓷立方氮化硼(CBN)砂块进行了磨粒划擦试验,试验结果证实了磨粒切削仿真结果的准确性。     

Influence of alumina abrasive tool wear on ground surface characteristics and corrosion properties of K444 nickel-based superalloy

K444 nickel-based superalloy is an important material to manufacture the gas turbine due to its excellent mechanical properties at high temperatures and corrosion resistance. Currently,grinding is the mostly used method for the surface finish of the K444 alloy components. However,few studies worked on the effects of the abrasive tool wear on the ground surface characteristics and corrosion properties of K444 alloy. This study uses two different-type alumina abrasive tools, i.e.,white alumina(WA)...     

Advances in fabrication of ceramic corundum abrasives based on sol–gel process

Corundum abrasives with good chemical stability can be fabricated into various free abrasives and bonded abrasive tools that are widely used in the precision machining of various parts. However, these abrasives cannot satisfy the machining requirements of difficult-to-machine materials with high hardness, high strength, and strong wearing resistance. Although superhard abrasives can machine the above-mentioned materials, their dressing and manufacturing costs are high. By contrast, ceramic corundum abrasives fabricated by sol–gel method is a cost-effective product between conventional and superhard abrasives. Ceramic corundum abrasives exhibit self-sharpening and high toughness. In this review, the optimization methods of ceramic corundum abrasive properties are introduced from three aspects: precursor synthesis, particle shaping, and sintering. Firstly, the functional mechanism of seeds and additives on the microstructural and mechanical properties of abrasives is analyzed. Specifically, seeds can reduce the phase transition temperature and improve fracture toughness. The grain size and uniformly dense structure can be controlled by applying an appropriate amount of multicomponent additives. Then, the urgent need of engineering application and machinability of special shape ceramic corundum abrasives is reviewed, and three methods of abrasive shaping are summarized. The micromold replication technique is highly advanced and can be used to prepare functional abrasives. Additionally, the influence of a new sintering method, namely, two-step sintering technique, on the microstructural and mechanical performance of ceramic corundum abrasives is summarized. Finally, the challenge and developmental trend of the optimization of ceramic corundum abrasives are prospected.