硬质合金涂层刀具车削钛合金TA15的磨损研究及切削参数优选

刀具磨损剧烈是钛合金切削中的突出问题,探求刀具磨损的本质对于提高加工质量和效率、降低成本具有重要意义。本文采用Al Ti N涂层硬质合金刀具对钛合金TA15(Ti-6.5Al-2Zr-1Mo-1V)进行车削试验,利用激光共聚焦显微镜观察刀具的磨损形貌,对刀具的主要磨损机理及磨损形式进行了分析,并根据刀具磨损状态进行了切削参数优选。研究结果表明:涂层硬质合金刀具切削TA15时,刀具失效形式主要为涂层剥落、崩刃和月牙洼磨损;随着切削速度的增加,后刀面VB值呈现了驼峰状的变化规律,涂层剥落的区域在波谷出现了明显的减小趋势;切削试验结果指出,正前角AlTiN涂层硬质合金刀具可用于钛合金TA15的精车工艺中,在v=100m/min、f=0.05mm/r、a_p=1.5mm切削参数下,刀具表现性能最优,同时硬质合金涂层刀具车削TA15的最大切削速度不宜超过120m/min。     

车削Ti_2AlNb金属间化合物刀片磨损形态及原因分析

采用不同刀尖圆弧半径的涂层硬质合金刀片对Ti_2AlNb金属间化合物材料进行车削试验研究,用扫描电子显微镜SEM观察刀片磨损形貌,通过能量分散光谱EDS分析刀片表面的元素分布及含量,并对刀片磨损形态和失效原因进行分析。研究结果表明:切削Ti_2AlNb过程中,涂层硬质合金刀片磨损形态为前刀面磨损、后刀面磨损、沟槽磨损和崩刃以及涂层剥落等;增大刀尖圆角有利于提高刀片寿命,并且小刀尖半径硬质合金刀片以沟槽磨损为主,大刀尖半径硬质合金刀片以后刀面磨损为主;沟槽磨损主要原因是粘结磨损、氧化磨损、扩散磨损以及疲劳破坏;沟槽磨损初期以粘结磨损、氧化磨损为主,中后期以扩散磨损以及疲劳破坏为主;后刀面磨损主要原因是磨粒磨损和粘结磨损。     

浅孔钻硬质合金刀片槽型及涂层对切削性能的影响研究

选择三款不同槽型及涂层结构的可转位硬质合金涂层刀片对碳钢C45进行钻削实验,通过对实验的切削力、切屑变形及刀具磨损测试分析,研究浅孔钻硬质合金刀片槽型及涂层对切削性能的影响。结果表明:T1刀片具有更好的综合切削性能,W1、W2刀片前刀面更易发生粘结磨损;W1、W2刀片槽型反屑角θ较大,具有更好的排屑效果;从后三种刀片的刀面磨损情况来看,AlCrN+TiSiN复合结构涂层具有最长的钻削寿命,TiAlN涂层钻削寿命最短。     

PVD涂层硬质合金刀具加工2Cr13性能对比试验研究

在相同材质刀片基体上分别涂覆不同种类的PVD涂层制成试验刀片。采用光学显微镜、扫描电子显微镜SEM及能谱仪EDS等对刀片涂层进行对比分析,用试验刀片分别对2Cr13不锈钢进行高速干式铣削试验,分析各涂层对刀片磨损形貌及其损坏机理的影响,对比各刀片的切削寿命,以优选出最佳涂层。分析结果表明,未涂层的刀片寿命最低,Ti Si N/Ti Al N涂层为最佳涂层,Ti Al Si N涂层刀片高温性能较好,双层结构Al Ti N涂层较Ti Al Cr N涂层和单层Al Ti N涂层表现出更好的耐磨性和高温性能。     

涂层刀具切削马氏体不锈钢的磨损机理研究

采用Al Ti N涂层硬质合金刀具对1Cr11Ni2W2MoV以及2Cr13两种型号的不锈钢进行车削试验,利用激光共聚焦显微镜观察刀具的前、后刀面磨损形貌,对刀具的主要磨损机理及磨损形式进行分析。研究结果表明:1Cr11Ni2W2MoV的加工难度大于2Cr13;硬质合金刀具切削1Cr11Ni2W2MoV不锈钢时,刀具主要的磨损形式为月牙洼磨损以及边界磨损,失效形式主要为崩刃;切削2Cr13不锈钢时,刀具的主要磨损机理为粘结磨损。     

陶瓷涂层刀具切削灰铸铁的试验研究

为了探究陶瓷涂层刀具涂层材质、基体材质对切削性能的影响,试验采用四种陶瓷涂层刀具连续干切削灰铸铁,测试了切削力和切削温度的变化情况以及后刀面的磨损量和已加工表面的粗糙度。结果表明,在刀具基体同为Si_3N_4的条件下,涂层材质为Ti N/Al_2O_3/Ti C的刀具比Ti N/Al_2O_3的切削性能好;在涂层材质同为Ti N的条件下,刀具基体Al_2O_3/Ti CN比Al_2O_3/Ti C的切削性能好。研究发现:四种陶瓷涂层刀具前刀面磨损形式均为微崩刃和月牙洼,后刀面磨损形式均为磨粒磨损和粘着磨损,涂层的磨损形式均为剥落和扩散磨损。     

用于难加工材料高效切削异面涂层刀具的研制

针对切削难加工材料时刀具前后刀面磨损机理不同、刀具寿命较短的问题,提出了在刀具前后刀面分别制备不同性能涂层的新方法,并对制备的异面涂层刀具进行了切削性能试验。首先对切削难加工材料时刀具磨损机理进行了研究,结果表明,刀具前刀面易于发生粘结磨损,后刀面易于发生磨粒磨损;然后,通过多弧离子镀方法,在前刀面制备了抗粘结能力强的Al Cr N多元涂层,在后刀面上制备了抗磨粒磨损能力强的Ti CN涂层。最后,对制备好的刀具进行了切削性能测试,结果表明,异面涂层能显著提高刀具的综合力学性能。     

涂层刀具硬态车削H13钢温度场模拟研究

基于有限元方法建立了H13钢硬态车削的仿真模型,应用Ti N、Ti C、Ti Al N、Al2O3涂层刀具对硬态切削H13钢在切削速度100-400m/min范围内的切削温度进行了模拟研究,重点分析了刀具前刀面上关键点的温度变化趋势及切削速度对该点温度的影响。仿真结果表明:涂层材料对切削温度产生一定影响,Ti C涂层刀具切削时温度最低;切削速度对切削温度有直接影响,切削速度越高,切削温度越高,越容易形成锯齿形切屑;刀具前刀面温度最高点出现在前刀面靠近刀尖的一点,即容易形成月牙洼磨损的位置。     

TiB2基陶瓷刀具切削不锈钢时的切削性能研究

研究了新型TiB2基陶瓷刀具切削奥氏体不锈钢1Cr18Ni9Ti时的切削性能.研究发现:BT30刀具表现出良好的切削性能.其中采用0°前角的刀具比-5°前角的刀具表现出更好的耐磨性.刀具的磨损形式为后刀面磨损和前刀面磨损,后刀面磨损机理为磨粒磨损,前刀面磨损机理为扩散磨损.     

织构化AlCrN涂层刀具车削加工奥氏体沉淀硬化不锈钢的切削性能研究

在基体为WC基硬质合金的Al Cr N涂层刀具前刀面应用激光技术加工出平行于切削刃的微织构,制备Al Cr N涂层织构化刀具;在液体润滑条件下对奥氏体沉淀硬化不锈钢(0Cr15Ni25Ti2Mo Al VB)进行切削试验,研究其切削性能,并与传统Al Cr N涂层刀具进行比较。分析了切削速度对切削力及切削温度的影响,并采用扫描电子显微镜(SEM)与X射线能谱仪(EDS)观察刀具的磨损形貌。研究结果表明:与传统Al Cr N涂层刀具相比,Al Cr N涂层织构化刀具能够有效降低切削温度、切削力和刀—屑接触面摩擦因数;由于微织构的存在,液体润滑时,润滑剂能够渗入到Al Cr N涂层织构化刀具的刀—屑接触面,因而具有良好的抗粘着性及耐磨性。     

TiAlN涂层硬质合金刀具铣削35CrMoSiV钢的切削性能研究

采用有和无PVD TiAlN涂层的细晶硬质合金铣刀对35CrMoSiV合金钢进行了干式端面铣削试验。分别测量了有、无涂层情况下铣刀后刀面径向磨损量和加工槽的表面粗糙度,通过光学显微镜观察了切屑,利用扫描电子显微镜(SEM)和电子能谱(EDX)分析了后刀面的磨损形态。研究结果表明:TiAlN涂层明显提高了硬质合金刀具的切削性能;硬质合金刀具后刀面磨损机制主要为粘着磨损和磨粒磨损,而涂层损伤是粘着磨损、剥层和氧化磨损共同作用的结果;在正常工作区内,提高铣削的转速和进给量,有利于减轻刀具的粘着,提高切削效率和质量。     

Experimental investigations on machinability aspects in finish hard turning of AISI 4340 steel using uncoated and multilayer coated carbide inserts

The present work deals with some machinability studies on flank wear, surface roughness, chip morphology and cutting forces in finish hard turning of AISI 4340 steel using uncoated and multilayer TiN and ZrCN coated carbide inserts at higher cutting speed range. The process has also been justified economically for its effective application in hard turning. Experimental results revealed that multilayer TiN/TiCN/Al₂O₃/TiN coated insert performed better than uncoated and TiN/TiCN/Al₂O₃/ZrCN coated carbide insert being steady growth of flank wear and surface roughness. The tool life for TiN and ZrCN coated carbide inserts was found to be approximately 19 min and 8 min at the extreme cutting conditions tested. Uncoated carbide insert used to cut hardened steel fractured prematurely. Abrasion, chipping and catastrophic failure are the principal wear mechanisms observed during machining. The turning forces (cutting force, thrust force and feed force) are observed to be lower using multilayer coated carbide insert in hard turning compared to uncoated carbide insert. From 1st and 2nd order regression model, 2nd order model explains about 98.3% and 86.3% of the variability of responses (flank wear and surface roughness) in predicting new observations compared to 1st order model and indicates the better fitting of the model with the data for multilayer TiN coated carbide insert. For ZrCN coated carbide insert, 2nd order flank wear model fits well compared to surface roughness model as observed from ANOVA study. The savings in machining costs using multilayer TiN coated insert is 93.4% compared to uncoated carbide and 40% to ZrCN coated carbide inserts respectively in hard machining taking flank wear criteria of 0.3 mm. This shows the economical feasibility of utilizing multilayer TiN coated carbide insert in finish hard turning.     

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.     

Wear mechanism of coated tools in the turning of ductile cast iron having wide range of tensile strength

In this study different specimens of ductile cast iron with tensile strength ranking from 400 MPa to 675 MPa were turned with K15 carbide, TiN coated and TiAlN coated tool in order to investigate wear mechanism and performance. Cutting forces and cutting temperature were similar for both coated tools, however flank wear and BUE were the lowest on the TiAlN coated tool, for this reason the TiAlN coated tool is suitable in the machining of ductile cast iron. The proposed tool wear mechanism is based on like-intermittent cutting caused by the pass from hard matrix to the soft graphite occasioning wear by adhesion. The analysis of the flank wear on coated tools is proposed by means of the wear curves in logarithmic scale instead of the usual linear scale. In this way, the change in wear rate is easily observed. This phenomenon was related with the wear out of the coating layer. The partial loss of the coating layer on cutting edge was confirmed by the EDS mapping images and SEM photographs.     

A comparative study on performance of multilayer coated and uncoated carbide inserts when turning AISI D2 steel under dry environment

The present work deals with a comparative study on flank wear, surface roughness, tool life, volume of chip removal and economical feasibility in turning high carbon high chromium AISI D2 steel with multilayer MTCVD coated [TiN/TiCN/Al₂O₃/TiN] and uncoated carbide inserts under dry cutting environment. Higher micro hardness of TiN coated carbide samples (1880 HV) compared to uncoated carbide (1430 HV) is observed and depicts better resistance against abrasion. The low erosion rate was observed in TiN coated insert compared to uncoated carbide. The tool life of TiN coated insert is found to be approximately 30 times higher than the uncoated carbide insert under similar cutting conditions and produced lower surface roughness compared to uncoated carbide insert. The dominant wear mechanism was found to be abrasion and progression of wear was steady using multilayer TiN coated carbide insert. The developed regression model shows high determination coefficient i.e. R² = 0.977 for flank wear and 0.94 for surface roughness and accurately explains the relationship between the responses and the independent variable. The machining cost per part for uncoated carbide insert is found to be 10.5 times higher than the multilayer TiN coated carbide inserts. This indicates 90.5% cost savings using multilayer TiN coated inserts by the adoption of a cutting speed of 200 m/min coupled with a tool feed rate of 0.21 mm/rev and depth of cut of 0.4 mm. Thus, TiN coated carbide tools are capable of reducing machining costs and performs better than uncoated carbide inserts in machining D2 steel.     

Performance studies of multilayer hard surface coatings (TiN/TiCN/Al2O3/TiN) of indexable carbide inserts in hard machining: Part-I (An experimental approach)

In recent years, hard machining using CBN and ceramic inserts became an emerging technology than traditional grinding and widely used manufacturing processes. However the relatively high cost factors associated with such tools has left a space to look for relatively low cost cutting tool materials to perform in an acceptable range. Multilayer coated carbide insert is the proposed alternative in the present study due to its low cost. Thus, an attempt has been made to have an extensive study on the machinability aspects such as flank wear, chip morphology, surface roughness in finish hard turning of AISI 4340 steel (HRC 47 ± 1) using multilayer coated carbide (TiN/TiCN/Al₂O₃/TiN) insert under dry environment. Parametric influences on turning forces are also analyzed. From the machinability study, abrasion and chipping are found to be the dominant wear mechanism in hard turning. Multilayer TiN coated carbide inserts produced better surface quality and within recommendable range of 1.6 μm i.e. comparable with cylindrical grinding. At extreme parametric conditions, the growth of tool wear was observed to be rapid thus surface quality affected adversely. The chip morphology study reveals a more favorable machining environment in dry machining using TiN coated carbide inserts. The cutting speed and feed are found to have the significant effect on the tool wear and surface roughness from ANOVA study. It is evident that, thrust force (Fy) is the largest component followed by tangential force (Fz) and the feed force (Fx) in finish hard turning. The observations yield the machining ability of multilayer TiN coated carbide inserts in hard turning of AISI 4340 steel even at higher cutting speeds.     

INVESTIGATION OF THE TOOL WEAR AND SURFACE FINISH IN LOW-SPEED MILLING OF STAINLESS STEEL UNDER FLOOD AND MIST LUBRICATION

This paper examines the performance of AlN/TiN coated carbide tool during milling of STAVAX® (modified AISI 420 stainless steel) at a low speed of 50 m/min under conventional flood and mist lubrication. Abrasion, chipping, fracture resulting in the formation of crater and catastrophic failure are the wear mechanisms encountered during machining under flood lubrication. The flank wear, and the likeliness of the cutting tool to fracture, chip and fail prematurely increased with an increase in the hardness of the workpiece and a reduction in the helix angle of the tool. Small quantity of mineral oil sprayed in mist form was effective in reducing the flank wear and severity of abrasion wear, and preventing the formation of crater and the occurrence of catastrophic failure. In milling 35 and 55 HRC-STAVAX® using a feed rate of 0.4 mm/tooth and a depth of cut of 0.2 mm under mist lubrication, the cutting edge of the 25° and 40° helix angle tools only suffered small-scale edge chipping and abrasive wear throughout the entire duration of testing. The influence of the ductility of the workpiece on the surface finish and the effectiveness of mist lubricant in improving the surface finish are also discussed.     

小直径铣刀铣削淬硬钢深窄型腔的实验研究

采用Φ2 mm TiAlN涂层硬质合金铣刀对S136淬硬模具钢的深窄型腔进行中高速干式切削实验,研究走刀方式、螺旋下刀半径、螺旋角、切削深度、切削速度、进给速度等因素对切削力和振动的影响规律,为优化小直径铣刀铣削高硬材料模具深窄型腔的工艺参数提供依据.     

Performance evaluation of PVD TIALN coated carbide tools vis-à-vis uncoated carbide tool in turning of titanium alloy (Ti-6Al-4V) by simultaneous minimization of cutting energy,dimensional deviation and tool wear

Titanium alloys are difficult-to-machine materials because of their poor machinability characteristics. Machining and machining performance evaluation for such materials is still a challenge. Individual machining performance indices like cutting forces, cutting energy and tool wear lead to ambiguous understanding. In this work, a Cumulative Performance Index (CPI) is defined which amalgamates non-dimensional forms of specific cutting energy, back force and average principal flank wear in turning. The CPI focuses upon simultaneous minimization of specific cutting energy, dimensional deviation and average principal flank wear. The defined index is then used to evaluate performance of five commercially available physical vapor deposited (PVD) TiAlN coated tungsten carbide/cobalt inserts vis-à-vis uncoated tungsten carbide/cobalt insert in turning of Ti-6Al-4V. Cutting forces were monitored during turning and tool wear was measured after turning experiments. The results showed that the performance of coated inserts was either comparable or poor than uncoated insert; and in no case, coated inserts performed better than uncoated insert. Although commercial recommendations are in place to use PVD coated inserts for enhanced machinability of titanium alloys, the use of coated inserts is not justified keeping in view the energy spent in coating and insignificant improvement in performance.     

HIGH SPEED MILLING OF GRAPHITE ELECTRODE WITH ENDMILL OF SMALL DIAMETER

Graphite becomes the prevailing electrode material in electrical discharging machining (EDM)currently.Orthogonal cutting experiments are carried out to study the characteristics of graph- ite chip formation process.High speed milling experiments are conducted to study tool wear and cutting forces.The results show that depth of cut has great influence on graphite chip formation.The removal process of graphite in high speed milling is the mutual result of cutting and grinding process. Graphite is prone to cause severe abrasion wear to coated carbide endmills due to its high abrasive- ness nature.The major patterns of tool wear are flank wear,rake wear,micro-chipping and breakage. Cutting forces can be reduced by adoption of higher cutting speed,moderate feed per tooth,smaller radial and axial depths of cut,and up cutting.