金刚石切削黑色金属时刀具磨损机理的摩擦磨损试验

为了降低黑色金属金刚石切削过程中的刀具磨损,提高表面加工质量和精度,对刀具磨损机理进行了研究.通过黑色金属金刚石摩擦磨损试验,模拟了实际切削过程中的刀具磨损行为;分别采用扫描电镜(SEM) 、X射线能谱仪(EDS)以及拉曼光谱仪(RS)对工件表面形貌、实验前后工件表面化学组分变化以及金刚石磨损表面的晶体结构转变进行了检测,同时提出了用石墨化程度作为试验过程中评价金刚石磨损的指标.试验结果表明:金刚石的磨损主要与机械力和温度有关,摩擦速度和工件材料中的含碳量对其影响相对较小;石墨化磨损、扩散磨损和氧化磨损等磨损机理共存,其中石墨化为导致金刚石磨损的主要原因.结合红外热像仪测温和热传导理论推算,近似获得了摩擦界面的真实温度,且随着温度升高15％,金刚石石墨化程度显著加剧83％.作者提出,应当综合考虑热-力耦合作用下的刀具磨损机理,以便进一步探寻抑制刀具磨损的工艺措施.     

Friction and wear of aluminium-silicon alloys

The friction and wear of aluminium-silicon alloys have been studied using a pin-on-disk machine together with metallographic investigations, microhardness testing and scanning electron microscopy. Silicon content does not appear to be a dominant factor in wear resistance. The eutectic alloy was the most wear resistant of the alloys studied. The predominant wear mode appears to be by separation of all or part of the work-hardened layers from random patches on the wear track. Nucleation sites for wear debris are probably created below the sliding surface as a result of Hertzian stressing.     

Wear behavior of natural diamond tool in cutting tungsten-based alloy

Natural diamond tool is quickly worn out while cutting a workpiece made of a tungsten-based alloy. This paper presents a new approach to reduce tool wear: ultrasonic vibration cutting of a workpiece made of a tungsten-based alloy based on gas–liquid atomization cooling. An atomizer is a device which mixes carbon dioxide gas with vegetable oil and changes the liquid into minute droplets, which are carried by a stream of gas. Atomizer is also a device that incorporates a venture device to translate liquid into a gas stream. The atomized minute droplets act as the cooling and lubricating medium to protect the tools. The system is designed to ensure that droplets can spread all over the surface of a work piece. At a constant spindle speed, feed rate, and cutting depth, the experiments were carried out for investigating the effects of the tool vibration parameters, carbon tetrachloride liquid flow rate, carbon dioxide gas flow, and gas–liquid mass ratio on the tool wear. The experiments showed that the technology of ultrasonic vibration with gas–liquid atomization cooling effectively prolongs the tool life in cutting tungsten-based alloy.     

Wear of a hypereutectic aluminium-silicon alloy

The influence of structural modification on the wear resistance of BS 1490 (1970) LM30, a hypereutectic aluminium-silicon alloy specifically recommended for the production of cast automobile cylinder blocks of monobloc construction, was assessed. Wear tests were carried out using a pin on ring wear test machine. Structural modification of the alloy was obtained by adding either sodium to modify the eutectic silicon, or sulphur to refine the primary silicon; sodium and sulphur were also added in combination in an attempt both to modify the eutectic silicon and to refine the primary silicon. Structural modification had no significant effect on the wear resistance of the alloy.     

Tool wear and its effect on surface roughness in diamond cutting of glass soda-lime

For the technology of diamond cutting of optical glass, the high tool wear rate is a main reason for hindering the practical application of this technology. Many researches on diamond tool wear in glass cutting rest on wear phenomenon describing simply without analyzing the genesis of wear phenomenon and interpreting the formation process of tool wear in mechanics. For in depth understanding of the tool wear and its effect on surface roughness in diamond cutting of glass, experiments of diamond turning with cutting distance increasing gradually are carried out on soda-lime glass. The wear morphology of rake face and flank face, the corresponding surface features of workpiece and the surface roughness, and the material compositions of flank wear area are detected. Experimental results indicate that the flank wear is predominant in diamond cutting glass and the flank wear land is characterized by micro-grooves, some smooth crater on the rake face is also seen. The surface roughness begins to increase rapidly, when the cutting mode changes from ductile to brittle for the aggravation of tool wear with the cutting distance over 150 m. The main mechanisms of inducing tool wear in diamond cutting of glass are diffusion, mechanical friction, thermo-chemical action and abrasive wear. The proposed research makes analysis and research from wear mechanism on the tool wear and its effect on surface roughness in diamond cutting of glass, and provides theoretical basis for minimizing the tool wear in diamond cutting brittle materials, such as optical glass.     

Monitoring of diamond disk wear in stone cutting by means of force or acceleration sensors

The application of sensor systems is becoming more commonplace in improving productivity, automation, and reliability. The sensors employed in such systems possess signal and information ability for enhancing the monitoring and control of machining processes. Although measuring force and acceleration signals have been commonly used for the monitoring of metal machining processes, their application to stone cutting has not been well developed, which is perhaps due to the complexity of the interaction between the stone and the diamond disk. In order to enhance knowledge in this area of applications, a multi-sensor system was developed and installed for the monitoring of stone cutting by diamond mill. The signals acquired and analysed by the system include force and acceleration under different machining conditions. The measured signal data was used to perform time-domain analysis. The results indicate the feasibility of using the RMS features of force or acceleration signals along z-axis for the monitoring of disk wear.     

Evaluation of diamond tool wear

The present study proposes a test protocol regarding the wear of sintered diamond tools. A set of parameters, which characterise the grade of wear, and its relationship with the cutting ability of the examined tools, are established. The proposed protocol establishes the procedure and the equipment for carrying out the tests, the features of the materials to use and the format of the report to present the results obtained. The developed test protocol indicates an universally applicable way for measurement of the wear of the diamond tool. It is an indispensable instrument for correctly carrying out the wear tests and for reliably interpreting the results. The protocol developed so far mainly regards laboratory tests, considering the slowness and precision of the measurements involved. Given the total absence of norms, this protocol could be absorbed by national and international norm establishing organisations. This protocol has also been applied to two types of tools and the results obtained have appeared reliable and replicable. The test protocol proposed in this study makes it possible to overcome the difficulties connected to the scarcity of technical data regarding the properties of the tool, which is typical in this field since the recipes for tool manufacturing are patented.     

The wear of diamond tools turning mild steel

Previous experiments on the wear of diamond tools turning mild steel have shown that the very high rates of wear of the diamond arise from the degeneration of the diamond to graphite, the details of the wear mechanisms depending on the cutting conditions. The present experiments on a larger number of tools show much greater differences in the wear rates of different diamonds than have been reported previously. It appears probable that these differences in wear rates arise from differences in the chemical constitution of the diamonds.     

金刚石刀具的研磨与切削实验

对四种不同材料的金刚石晶体 (天然单晶、MONODITE、CVD、PCD)进行了研磨和切削实验 ,获得了一些基础数据 ,并对实验结果分析。在研磨实验中对研磨方法、研磨效率及研磨的刀具刃口质量进行了比较 ,同时对这四种刀具进行切削实验———对有色金属进行精密加工     

Dry sliding wear of diamond materials

In pin-on-disc tests, diamond composites, consisting of diamonds imbedded in a silicon matrix, were run against themselves in air at a sliding speed of 125 cm s^?1 and for loads up to 3.6 kgf. In addition, a few experiments involving sintered diamond compacts rubbing against a rotating metal ring in a ring-and-block configuration were conducted. For the diamond composite wear tests, wear was found to be proportional to load and sliding distance for P ? 3.0 kgf. For both the diamond composite and the diamond compact, the wear rates were very low and similar to those previously observed for single-crystal diamonds rubbed by diamond and metal.     

Tool wear and cutting forces under cryogenic machining of titanium alloy (Ti17)

Titanium alloy is well known for its difficulty to machine, owing to the important “tool wear” phenomenon. Machining assistance is an interesting solution to lengthen the tool lifetime. In this study, we focused on the effect of cryogenic assistance—during machining of Ti17—on the tool wear and cutting forces for different combinations of cutting speed, feed rate and depth of cut. Compared to conventional lubrication, cryogenic support lengthens the tool life for all tested conditions and has no significant influence on cutting force. A comparison of the cryogenic effect and high-pressure water jet assistance is also presented.     

Analytical prediction of cutting tool wear

An analytical method is presented which enables the crater and flank wear of tungsten carbide tools to be predicted for a wide variety of tool shapes and cutting conditions in practical turning operations based only on orthogonal cutting data from machining and two wear characteristic constants. A wear characteristic equation is first derived theoretically and verified experimentally. An energy method is developed to predict chip formation and cutting forces in turning with a single-point tool from the orthogonal cutting data. Using these predicted results, stress and temperature on the wear faces can be calculated. Computer simulation of the development of wear is then carried out by using the characteristic equation and the predicted stresses and temperatures upon the wear faces. The predicted wear progress and tool life are in good agreement with experimental results.     

Influence of cutting speed on cutting force,flank temperature,and tool wear in end milling of Ti-6Al-4V alloy

Tool wear is one of the most important problems in cutting titanium alloys due to the high-cutting temperature and strong adhesion. Recently, the high-speed machining process has become a topic of great interest for titanium alloys, not only because it increases material removal rates, but also because it can positively influence the properties of finished workpiece. However, the process may result in the increase of cutting force and cutting temperature which will accelerate tool wear. In this paper, end milling experiments of Ti-6Al-4V alloy were conducted at high speeds using both uncoated and coated carbide tools. The obtained results show that the cutting force increases significantly at higher cutting speed whether the cutter is uncoated carbide or TiN/TiAlN physical vapor deposition (PVD)-coated carbide. For uncoated carbide tools, the mean flank temperature is almost constant at higher cutting speed, and no obvious abrasion wear or fatigue can be observed. However, for TiN/TiAlN PVD-coated carbide tools, the mean flank temperature always increases as the increase of cutting speed, and serious abrasion wear can be observed. In conclusion, the cutting performance of uncoated inserts is relatively better than TiN/TiAlN PVD-coated inserts at a higher cutting speed.     

Study of wear rate of cutting tools made from Cr-based high-temperature alloy during operation depending on the material properties of the cutting tool and the rate of cutting

In the work, the wear rate of cutting tools made of hard alloy, cutting ceramics, and ultra-hard materials has been studied. The slowest wear rate is achieved using hard-alloy, with the bonding of hard-melting metal in the composition.     

The friction and wear properties of polytetrafluoroethylene filled with ultrafine diamond

The friction and wear properties of polytetrafluoroethylene (PTFE) filled with ultrafine diamond (UFD) were studied in detail on a block-on-ring wear tester under dry sliding conditions. Transmission electron microscope (TEM) was used to research microstructure of the purchased UFD and the purified UFD. Scanning electron microscope (SEM) and differential scanning calorimetry (DSC) were utilized to investigate material microstructures and examine modes of failure. Experimental results showed that there was no significant change in coefficient of friction, but the wear rate of the PTFE composite was orders of magnitude less than that of pure PTFE with increasing purified UFD content. Analysis of SEM indicated UFD in PTFE matrix had effects of loading-carry and increasing formation of transfer films on the steel counterpart surface as well as inhabiting generation of bigger debris. Furthermore, DSC disclosed that the PTFE composite with higher heat absorption capacity exhibited improved wear resistance. Wear mechanism was probably that UFD particles had a function of rolling bearing in frictional interface, and resulted in change of PTFE frictional form from single macromolecular sliding friction to a mixed form of sliding and rolling friction, accordingly UFD in PTFE could obviously decrease wear of pure PTFE.     

Effects of cutting parameters on tool insert wear in end milling of titanium alloy Ti6Al4V

Titanium alloy is a kind of typical hard-to-cut material due to its low thermal conductivity and high strength at elevated temperatures, this contributes to the fast tool wear in the milling of titanium alloys. The influence of cutting conditions on tool wear has been focused on the turning process, and their influence on tool wear in milling process as well as the influence of tool wear on cutting force coefficients has not been investigated comprehensively. To fully understand the tool wear behavior in milling process with inserts, the influence of cutting parameters on tool wear in the milling of titanium alloys Ti6Al4V by using indexable cutters is investigated. The tool wear rate and trends under different feed per tooth, cutting speed, axial depth of cut and radial depth of cut are analyzed. The results show that the feed rate per tooth and the radial depth of cut have a large influence on tool wear in milling Ti6Al4V with coated insert. To reduce tool wear, cutting parameters for coated inserts under experimental cutting conditions are set as: feed rate per tooth less than 0.07 mm, radial depth of cut less than 1.0 mm, and cutting speed sets between 60 and 150 m/min. Investigation on the relationship between tool wear and cutting force coefficients shows that tangential edge constant increases with tool wear and cutter edge chipping can lead to a great variety of tangential cutting force coefficient. The proposed research provides the basic data for evaluating the machinability of milling Ti6Al4V alloy with coated inserts, and the recommend cutting parameters can be immediately applied in practical production.