球头铣刀高速切削Inconel 718的刀具磨损研究

为了实现航空高温合金的高速高效加工,通过对Inconel718的铣削试验,分析了涂层球头铣刀切削高温合金时的加工性能。试验结果表明,乳化液在90m/min的切削速度下仍然具有较好的冷却润滑作用。通过对TiAlN涂层和TiAlN+Al2O3涂层刀具的对比试验,证明TiAlN涂层具有优异的耐磨性,可显著提高加工高温合金时的刀具寿命。     

Effect of cutting speed on surface integrity and chip morphology in high-speed machining of PM nickel-based superalloy FGH95

High-speed machining is being recognized as one of the key manufacturing technologies for getting higher productivity and better surface integrity. FGH95 powder metallurgy superalloy is a kind of nickel-based superalloy which is produced by near-net-shape technology. With increasing demands for high precision and high performance of FGH95 components in aerospace industry, it is essential to recognize that the machined surface integrity may determine machined part service performance and reliability. Then, little is known about the machined surface integrity of this superalloy. Thus, the surface integrity in high-speed machining of FGH95 is investigated in this paper. Experiments are conducted on a CNC milling center with coated carbide tools under dry cutting conditions. The surface integrity is evaluated in terms of surface roughness, microhardness, and white layer. The influence of cutting speed on chip morphology is also investigated. Experiment results show that surface integrity and chip morphology of FGH95 are very sensitive to the cutting speed. When cutting speeds are below 2,400?m/min, the values of surface roughness have little variation, while when cutting speeds are in the range of 2,800–3,600?m/min, the values of surface roughness are higher than that of other cutting speeds. Severe work hardening is observed resulting from high-speed machining of FGH95 superalloy. The higher the cutting speed, the higher the surface hardness. When cutting speeds are in the range of 2,800–3,600?m/min, the white layer thickness is slightly higher than that of other cutting speeds. In high-speed machining of FGH95, the chip is segmented and has a typical sawtooth shape. The degree of serrated chip increases with the cutting speed. When the cutting speeds exceed 2,400?m/min, serrated chips change into fragment chips.     

硬质合金铣刀涂层性能的试验研究

针对涂层材料改善刀具切削性能这一问题,本文采用常速试验和高速试验的方法,对比分析了七种涂层材料对铣刀切削性能的改善程度。试验结果表明:涂层性能优越与否与切削速度有很大关系,AlCrN和TiAlCN涂层铣刀更适合高速切削;而AlTiN涂层铣刀不适合高速切削;TiN涂层铣刀无论在常速和高速切削时性能均表现不佳,高速切削时磨损相对更快;CrN+TiN复合涂层抗氧化能力较好,但抗磨能力相对较差。     

Cutting performance of coated carbide tools in high-speed face milling of AISI H13 hardened steel

In the present study, high-speed face milling of AISI H13 hardened steel was conducted to investigate the cutting performance of coated carbide tools. The characteristics of chip morphology, tool life, tool wear mechanisms, and surface roughness were analyzed and compared for different cutting conditions. It was found that as the cutting speed increased, the chip morphology evolved in different ways under different milling conditions (up, down, and symmetric milling). Individual saw-tooth segments and sphere-like chip formed at the cutting speed of 2,500 m/min. Owing to the relatively low mechanical load, longest tool life can be obtained in up milling when the cutting speed was no more than 1,000 m/min. As the cutting speed increased over 1,500 m/min, highest tool life existed in symmetric milling. When the cutting speed was 500 m/min, owing to the higher mechanical load, the flaked region on the tool rake face in symmetric milling was much larger than that in up and down milling. There was no obvious wear on the tool rake face at the cutting speed of 2,500 m/min due to the short tool-chip contact length. In symmetric milling, the delamination of tool material, which did not occur in up and down milling, was caused by the relatively large cutting force. Abrasion had great effect on the tool flank wear in symmetric milling. With the increment of cutting speed, surface roughness decreased first and then increased rapidly. Lowest surface roughness can be obtained at the cutting speed of about 1,500 m/min.     

切削参数对粗精铣合体刀具铣削加工表面质量的影响

采用硬质合金刀具,通过单因素实验对铸铝材料的表面铣削加工过程进行研究,获得最佳的切削参数,提高加工表面质量。实验以粗精铣一次完成工艺代替粗加工—精加工分步完成的加工工艺,研究粗精铣合体刀具加工中最佳的切削参数组合。实验结果表明,对于铸铝零件,切削加工的最佳切削参数组合为:切削速度v=3000r/min、进给量f=1000mm/min、背吃刀量a p=0.3mm。通过比较不同工艺下切削参数与表面质量之间的关系,得出在相同表面质量的要求下,粗精铣合体刀具在铣削过程可简化加工工艺,缩短加工时间。     

铣削TC4钛合金的刀具磨损对比试验

TC4钛合金是典型难加工材料之一,极易造成工具磨损。本文通过铣削TC4钛合金试验,跟踪铣削过程中铣刀每个齿的磨损量及磨损形态,比较了不同细晶粒硬质合金铣刀的磨损过程。结果表明,铣刀切削刃发生崩刃会直接缩短铣刀的使用寿命。     

喷雾冷却和刀具表面涂层复合润滑在切削加工中的应用

采用喷雾冷却和固体润滑涂层两者复合的方法来进行切削加工，对切削温度和后刀面磨损量进行了测量，并用SEM和EDAX对刀具后刀面磨损形貌和成分进行分析。结果表明：在切削速度低于200m／min的情况下，单一的喷雾和固体润滑涂层对提高刀具的耐磨寿命有明显的作用；在切削速度高于200m／min后，单一的喷雾方法的减磨效果就大幅降低；当速度高于300m／min时单一使用几无效果，而复合法能明显提高刀具的耐磨寿命和加工精度。     

基于数控纵切自动车床上镍基高温合金的加工

随着航空航天工业的发展,对于高温合金工件的需求日益增长。针对镍基高温合金现场加工难、切削性能差和刀具磨损快等问题,本文在数控纵切自动车床上采用切削试验的方法,对镍基高温合金GH2132在不同切削工况下的刀具磨损以及零件表面质量进行了对比分析,明确了适用的刀具和合理的切削用量及切削速度。分析认为,性能优异的涂层刀具在选择了合适的进给量之后,完全能够满足镍基高温合金的切削加工,相对于其他硬质合金刀具,无论在生产效率还是产品质量方面,都有了很大的提升,并且节约了生产成本。     

Influence of laser heat treatment on microstructure and properties of surface layer of Waspaloy aimed for laser-assisted machining

In this study, a nickel-based superalloy, Waspaloy, was laser heat treated with diode laser. Single laser tracks were manufactured with different laser beam power densities between 63 and 331 kW/cm², and scanning laser beam speed ranged from 5 to 100 m/min. It was found that laser heat treatment of Waspaloy causes decrease in material hardness—the microhardness in laser tracks is about 300 HV0,1 while the microhardness of substrate is ranged from 300 to 600 HV0,1—which is a positive phenomenon for laser-assisted machining of investigated material. Impacts of laser heat treatment parameters on laser tracks properties were identified for obtaining multiple laser tracks with the most homogenous thickness. Moreover, roughness of heated layers was measured to specify surface quality after laser heat treatment. Multiple laser tracks were produced using different scanning laser beam speed and distances between laser tracks ranged from 0.125 to 1 mm. It was found that if scanning laser beam speed is 75 m/min and distance between laser tracks is equal to or lower than 0.25 mm, in microstructures of multiple laser tracks, cracks are occurring. The most suitable laser heat parameters for obtaining heated layers, and which can be used for laser-assisted machining, were identified as laser beam power density 178.3 kW/cm², scanning laser beam speed 5 m/min, and distance between laser tracks 0.125 mm.     

THE GEOMETRY, SPECIFICATION AND PREDICTIVE FORCE MODELS FOR PLANE FACED BALL-END MILLING CUTTERS AND OPERATIONS

In this paper the geometry and specification of ball-end milling cutters are studied and discussed followed by an outline of the development of computer-aided predictive models for the three force components, torque and power in plane faced ball-end milling operations, based on the 'Unified-Generalised Mechanics of Cutting Approach'. The models allow for six milling modes, namely; slotting, 'on-centre' end-milling and 'off-centre' end-milling, each machining at the cutter ball-end cutting edge only or at the cutter ball-end and cylindrical periphery cutting edges for two or more flute cutters. The models include all the tool and cut geometrical variables and the cutting speed as well as the tool-workpiece material combination (via the database of basic cutting quantities). The models are verified through extensive numerical simulation studies and a comprehensive experimental testing programme. Good qualitative and quantitative correlation has been found between predicted and measured fluctuating and average force components and torque.     

Evaluation on Effectiveness of CVD and PVD Coated Tools during Dry Machining of Incoloy 825

With wide applications of nickel-based superalloys in strategic fields, it has become increasingly necessary to evaluate the performance of different advanced cutting tools for machining such alloys. With a view to recommend a suitable cutting tool, the present work investigated various machinability characteristics of Incoloy 825 using an uncoated tool, chemical vapor deposition (CVD) of a bilayer of TiCN/Al₂O₃, and physical vapor deposition (PVD) of alternate layers of TiAlN/TiN-coated tools under varying machining conditions. The influence of cutting speed (51, 84, and 124 m/min) as well as feed (0.08, 0.14, and 0.2 mm/rev) was comparatively evaluated on surface roughness, cutting temperature, cutting force, coefficient of friction, chip thickness, and tool wear using different cutting tools. Although the CVD-coated tool was not useful in decreasing surface roughness and temperature, a significant reduction in cutting force and tool wear could be achieved with the same coated tool under a high cutting speed of 124 m/min. On the other hand, the PVD-coated tool outperformed the other tools in terms of machinability characteristics. This might be attributed to the excellent antifriction and antisticking property of TiN and good toughness due to the multilayer configuration in combination with a thermally resistant TiAlN phase. Adhesion, abrasion, edge chipping, and nose wear were the prominent wear mechanisms of the uncoated tool, followed by the CVD-coated tool. However, remarkable resistance to such wear was evident with the PVD TiAlN/TiN multilayer-coated tool.     

Influence of cutting speed on surface integrity for powder metallurgy nickel-based superalloy FGH95

Powder metallurgy (PM) nickel-based superalloy FGH95 has been widely used for components, which requires the greatest service performance. The surface integrity is becoming more and more important in order to satisfy the increasing service demands. However, the machined surface of FGH95 is easily damaged due to its poor machinability. The purpose of this paper is to investigate the effects of dry milling process parameters on the surface integrity of FGH95. Experiments were conducted on a CNC machining center under different cutting speeds. The machined surface is evaluated in terms of surface roughness, microhardness and white layer. Experiments results show milled surface integrity of FGH95 is sensitivity to the cutting speeds. The machined surface roughness decreases with increase of the cutting speed, but with further increase of cutting speed between 80?m/min to 100?m/min an increase in surface roughness appears. For microhardness, it can be seen that the machined workpiece surface hardens seriously. It can also draw the conclusion that cutting speed has the marginal effect on the white layer thickness generated in the machined subsurface.     

高速切削Ti6Al4V钛合金时切削温度的试验研究

应用硬质合金刀具对Ti6Al4V钛合金材料进行了高速车削和高速铣削试验,研究分析了干切削、空气射流及氮气射流条件下的切削温度变化情况。研究结果表明,氮气射流及空气射流条件下的切削温度明显低于干切削条件下的切削温度,而氮气射流条件下的钛合金高速切削温度则略低于空气射流条件下的切削温度。     

Failure mechanisms of a PCD tool in high-speed face milling of Ti–6Al–4V alloy

High-speed milling tests were carried out on Ti–6Al–4V titanium alloy with a polycrystalline diamond (PCD) tool. Tool wear morphologies were observed and examined with a digital microscope. The main tool failure mechanisms were discussed and analyzed utilizing scanning electron microscope, and the element distribution of the failed tool surface was detected using energy dispersive spectroscopy. Results showed that tool flank wear rate increased with the increase in cutting speed. The PCD tool is suitable for machining of Ti–6Al–4V titanium alloy with a cutting speed around 250 m/min. The PCD tool exhibited relatively serious chipping and spalling at cutting speed higher than 375 m/min, within further increasing of the cutting speed the flank wear and breakage increased greatly as a result of the enhanced thermal–mechanical impacts. In addition, the PCD tool could hardly work at cutting speed of 1,000 m/min due to the catastrophic fracture of the cutting edge and intense flank wear. There was evidence of workpiece material adhesion on the tool rake face and flank face in very close proximity to the cutting edge rather than on the chipped or flaked surface, which thereby leads to the accelerating flank wear. The failure mechanisms of PCD tool in high-speed wet milling of Ti–6Al–4V titanium alloy were mainly premature breakage and synergistic interaction among adhesive wear and abrasive wear.     

Morphology evolution and micro-mechanism of chip formation during high-speed machining

In this paper, the morphology and micro-mechanism of chip formation during high-speed machining aluminum alloy 7050-T7451 is investigated based on the combination of dislocation theory and plastic deformation theory. Experiments of quick stop stoppage for turning and special method (Buda) for milling process were carried out in order to obtain shear angle in different cutting speeds. The results show that effective flow stress and temperature in front edge zone is higher and more concentrated than that in other deformation zones. The shear front-lamellar structure was observed and analyzed in the front edge zone which influences the chip formation directly. The influence of cutting speed on chip formation was analyzed by simulation and experiments. Cutting speed is an important factor affecting the morphology evolution and chip formation. When the cutting speed is below 1500 m/min, the concentration of shear stress and the shear front-lamella structure of cutting deformation are more remarkable and easier for forming continuous ribbon chips. With the cutting speed increase, the ribbon chip transforms into serrated chip when a critical cutting speed (2500 m/min) is reached. Finally, microscopic mechanism of chip formation has been revealed and critical condition of the shear front—the layer structure formation—has been determined.     

Effect of cutting speed on cutting forces and wear mechanisms in high-speed face milling of Inconel 718 with Sialon ceramic tools

In this paper, a series of milling tests were carried out in order to identify the effects of cutting speed on cutting forces and tool wear when high-speed face milling Inconel 718 with Sialon ceramic tools. Both down-milling and up-milling operations were conducted. The cutting forces, tool wear morphologies, and the tool failure mechanisms in a wide range of cutting speeds (600–3,000 m/min) were discussed. Results showed that the resultant cutting forces firstly decrease and then increase with the increase of cutting speed. Under relatively lower cutting speeds (600 and 1,000 m/min), the dominant wear patterns is notching. Further increasing the speed to more than 1,400 m/min, the notching decreases a lot and flank wear becomes the dominant wear pattern. In general, at the same cutting speed, flaking on the rake face and notching on the flank face are more serious in down-milling operation than that in up-milling operation with the same metal removal volume. However, the surface roughness values for down-milling are lower than that for up-milling.     

THE SURFACE INTEGRITY IN MACHINING HARDENED STEEL SKD11 FOR DIE AND MOLD

Milling cutters were evaluated by tool wear, cutting force and vibration. Surface integrity of grinding and milling were investigated by comparing residual stress distributions, metallurgical structure, hardened layer depth and surface roughness. And influence of cutting tool wear on surface integrity was investigated. Experimentations revealed that the preferable surface integrity would be obtained if the proper milling cutter as well as a small wear criterion were adopted to avoid the advent of tempered martensite. The research results pointed out the feasibility of taking milling as the finish machining process instead of grinding in machining hardened steel with high efficiency.     

THE SURFACE INTEGRITY IN MACHINING HARDENED STEEL SKD11 FOR DIE AND MOLD

Milling cutters were evaluated by tool wear, cutting force and vibration. Surface integrity of grinding and milling were investigated by comparing residual stress distributions, metallurgical structure, hardened layer depth and surface roughness. And influence of cutting tool wear on surface integrity was investigated. Experimentations revealed that the preferable surface integrity would be obtained if the proper milling cutter as well as a small wear criterion were adopted to avoid the advent of tempered martensite. The research results pointed out the feasibility of taking milling as the finish machining process instead of grinding in machining hardened steel with high efficiency.     

3D FE modelling of high-speed ball nose end milling

The paper details research and development of a Lagrangian-based, 3D finite element (FE) model to simulate the high-speed ball nose end milling of Inconel 718 nickel-based superalloy using the commercial FE package ABAQUS Explicit. The workpiece material was modelled as elastic plastic with isotropic hardening and the flow stress defined as a function of strain, strain rate and temperature. Workpiece material data were obtained from uniaxial compression tests at elevated strain rates and temperatures (up to 100/s and 850°C, respectively) on a Gleeble 3500 thermo-mechanical simulator. The data were fitted to an overstress power law constitutive relationship in order to characterise flow behaviour of the material at the level of strain rates found in machining processes (typically up to 10⁵/s). Evolution of the chip was initially seen to progress smoothly, with the predicted machined workpiece contour showing good correlation with an actual chip profile/shape. Cutting force predictions from the FE model were validated against corresponding experimental values measured using a piezoelectric dynamometer, while modelled shear zone/chip temperatures were compared with previously determined experimental data. The model was successful in predicting the forces in the feed and step-over direction to within 10% of corresponding experimental values but showed a very large discrepancy with the thrust force component (～90%). Modelled shear-plane temperatures calculated at the point of maximum cutting force were found to demonstrate very good agreement with measured values, giving a discrepancy of ～5%. The simulation required a computational time of approximately 167 h to complete one full revolution of the ball end mill at 90 m/min cutting speed.     

加工复合材料铣刀的研制

复合材料的切削加工性很差,复合材料加工刀具已严重影响了复合材料的加工质量和效率。为解决复合材料的加工存在质量差和效率低的问题,笔者针对复合材料的加工性能、刀具材料及其结构,进行了系统的研究。掌握了加工复合材料铣刀的设计和制造技术,并通过对刀具结构参数的优化,提高了复合材料切削加工质量和效率。