纳米K2Ti4O9晶须增强型固体润滑涂层在切削加工中的应用

为了减少切削加工中切削液的排放 ,改善环境 ,本研究用固体润滑剂代替切削液。在高温摩擦试验机上对四种固体润滑剂进行了摩擦试验和效果对比 ,筛选出纳米钛酸钾增强型复合固体润滑剂 ;将其涂覆在刀具表面进行 4 0Cr钢切削试验 ,干切削中切削速度为 14 0m/min时涂层刀具的后刀面磨损量是未涂层刀具的 1/ 6 ,比使用切削液时的磨损量也略有降低 ;随着切削速度的升高 ,涂层刀具的后刀面磨损量有所增加 ,但仍比未涂层的低 ,比使用润滑液的有所增高。AFM、SEM和EDX对摩擦表面的分析结果表明 :固体润滑膜涂覆在刀具表面 ,可改善刀具的润滑状况 ,有效地防止切屑和刀具的粘附 ,明显减少刀具的磨损     

蠕墨铸铁切削中高压切削液对刀具磨损的影响

蠕墨铸铁是内燃机主要结构材料之一,是一种较难加工材料。针对蠕墨铸铁加工中切削温度高、刀具磨损严重等难题,提出在切削液高压喷射条件下对蠕墨铸铁车削加工的方案。即在切削液不同喷射路径、不同切削速度条件下,结合干切削对比,研究了高压切削液对刀具后刀面磨损量影响试验,并用超景深三维显示系统对在不同喷射路径下的刀具前后刀面磨损形貌进观察分析。通过试验表明:在不同喷射路径下,高压切削液从后刀面喷射比前刀面喷射对减少后刀面的磨损量效果好。对于前、后刀面磨损形貌,切削液高压喷射冷却润滑能很好的抑制前刀面月牙洼磨损,同时能有效降低后刀面的粘结氧化等热化学磨损,较好的延长整个刀具寿命。在不同切削速度干、湿切削对比,高压湿切削对后刀面减磨效果会随着切削速度升高而增大,在切削速度V_c=300m/min减磨效果最明显。     

TiN涂层刀具切削高锰钢的磨损破损研究

研究奥氏体高锰钢切削过程中TiN涂层硬质合金刀具的磨损、破损机制,测量了切削温度并得出后刀面磨损量与 切削时间和切削速度的关系曲线,以及刀具前、后刀面显微磨损、破损形貌和化学变化。结果表明,TiN涂层硬质合金刀 具切削奥氏体高锰钢时耐磨性优于单一硬质合金刀具,且适于低速切削(小于30m/min)。     

硬质合金正交车铣TC4钛合金刀具寿命试验分析

在Mazak Integrex 200Y车铣复合加工中心上,在顺铣干切和切削液条件下,在v=150和200 m/min两种切削速度下,采用未涂层硬质合金H13A和涂层硬质合金S30T分别对TC4钛合金进行正交车铣刀具寿命试验,试验结果表明,当达到磨钝标准0.3 mm时,S30T涂层硬质合金在切削速度为150 m/min时,切削路程相当,切削液对刀具寿命的影响不明显,切削速度为200 m/min时,切削液条件下,刀具的寿命延长,但随着切削速度的提高,刀具寿命剧降。H13A未涂层硬质合金在两种切削速度下,切削液条件下,刀具寿命比干切削短,切削液加剧了刀具磨损,缩短刀具寿命,并得出H13A未涂层硬质合金更适合正交车铣TC4钛合金的结论。试验还研究了轴向进给量fa变化对H13A未涂层硬质合金正交车铣TC4钛合金刀具寿命的影响趋势,生产中应兼顾生产率和刀具寿命,合理选择轴向进给量。     

切削速度对微织构涂层刀具切削性能的影响

为了探究前后刀面微织构涂层刀具在不同切削速度下的切削性能变化规律,利用光纤式激光器在涂层刀具的前刀面和后刀面上分别制备出圆孔和直槽混合微织构,使用该刀具在38CrMoAl氮化钢上进行切削实验。结果表明,随着切削速度的增加,无织构刀具和前刀面织构刀具的切削温度变动范围不大,前后刀面混合微织构刀具的切削温度最大值比无织构刀具的切削温度最大值降低了13%～27%;织构刀具切削力的降低幅度,随着切削速度的增加而增加,相对于无织构刀具的切削力,其最大降幅近40%;在切削速度为80 m/min时,织构刀具对应的表面粗糙度值几乎相等,在其他切削速度时,前后刀面织构刀具对应的表面粗糙度值均小于前刀面织构刀具对应的值,并且表面粗糙度值随着切削速度的增加而降低;振动信号结束段和起始段频谱幅值的变化范围随着切削速度的增加而变得明显。与无织构刀具相比,织构刀具在不同切削速度下均可以改善刀具的切削性能,特别是后刀面织构的存在,这种改善效果更加明显。     

涂层硬质合金正交车铣TC4钛合金刀具寿命试验分析

在Mazak Integrex 200Y车铣复合加工中心上,顺、逆铣干切和切削液条件下,取v=150、200m/min两种切削速度,采用涂层硬质合金S30T对TC4钛合金进行正交车铣刀具寿命试验。试验结果表明,当达到磨钝标准0.3mm时,在切削速度为150m/min时,顺铣干切和切削液条件下,逆铣干切及切削液条件下,切削路程都相差不明显,切削液对刀具寿命的影响不大;切削速度为200m/min时,顺铣干切和切削液条件下,切削路程相差明显,使用切削液条件下刀具的寿命延长;逆铣干切和切削液条件下,切削路程相差不明显,切削液对刀具寿命的影响不大。通过对比得出S30T正交车铣TC4钛合金时优先选用顺铣切削液加工方式。     

铣削等温淬火球墨铸铁的切削力及刀具磨损研究

对PCBN刀具在干切削状态下铣削ADI的切削力和刀具磨损进行了试验研究。分析了切削速度分别为40、80、120、160、200 m/min条件下的切削力和不同行程下刀具后刀面磨损量的变化规律。结果表明PCBN切削ADI材料的最佳切削速度在80 m/min~160 m/min之间。     

高速铣削AISI 4340合金结构钢时涂层刀具磨损机理研究

针对AISI 4340合金结构钢难加工的特点,选用PVD硬质合金涂层刀具进行高速干铣削试验,选用扫描电子显微镜(SEM)观察失效刀具表面的磨损形貌特征,选用能谱分析仪(EDS)分析磨损刀具表面的元素分布及含量,揭示刀具的磨损机理。研究结果表明:刀具寿命与切削参数选取有关,随着切削速度的增加,刀具磨损加快,刀具寿命降低。硬质合金涂层刀具的主要磨损形式是前刀面磨损和后刀面磨损,前刀面磨损机理主要是粘结磨损、涂层剥落、切削刃微崩刃;后刀面磨损机理主要是磨粒磨损、粘结磨损、扩散磨损、微裂纹。     

高速车削300M高强度钢涂层刀具失效机理研究

选用不同涂层刀具进行高速切削300M钢试验,利用工具显微镜和电子扫描显微镜(SEM)观察刀具磨损形貌,并利用线扫描进行元素扩散分析,揭示刀具失效机理。研究结果表明:金属陶瓷基涂层刀具高速切削时,切削速度不宜超过240m/min;硬质合金基涂层刀具可在300m/min以上高速切削300M钢,其中CVD-Ti CNAl2O3厚涂层的高速切削性能更高,切屑塑形变形较小;涂层刀具切削300M钢的主要磨损形式是前刀面磨损和后刀面磨损,涂层剥落、崩刃、微裂纹、粘结磨损、磨粒磨损、氧化磨损、扩散磨损是刀具失效的主要原因。     

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。     

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.     

Milling of MAR-M247 nickel-based superalloy with high temperature and ultrasonic aiding

This study investigates the properties of machining MAR-M247 nickel-based superalloy combined ultrasonic vibration with high-temperature aided cutting. Taguchi experimental design was adopted to identify the influence of machining parameters on the machining characteristics. The six machining parameters, namely cutting tools for different materials; depth of cut; cutting speed; feed rate; working temperature; and, ultrasonic power. The machining characteristics analyzed include surface roughness, flank wear, cutting force, and milling temperature. According to the experimental results, when the cutting speed is greater than 90 m/min, P-type tungsten-carbide cutters with or without a Ti-alloy coating were unable to endure the very high temperatures generated in milling MAR-M247 nickel-based superalloy. The tungsten-carbide cutters melted and fractured. Due to the insufficient toughness of cermet cutters, the periodic high-impact stress causes severe cutter fractures when the cutting speed is greater than 60 m/min. When the cutting speed was less than 40 m/min, the cutter temperature was not significantly increased. Thus no melting or fracture of the cutters was found. Furthermore, when the cutting speed was less than 40 m/min, and fluid containing nano-particles of 5–23 nm in size was used, the cutter-workpiece friction force was reduced and the cutter life was extended.     

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.     

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.     

PCBN刀具高速切削抗氢钢HR-2的性能研究

采用不同CBN含量和晶粒结构的PCBN刀具,在不同切削速度下进行了HR-2抗氢钢的高速精密切削试验。通过对PCBN刀具前、后刀面的显微形貌特征进行观测,分析了刀具的失效磨损机理,研究了不同CBN含量及不同切削速度对刀具使用寿命的影响。对刀具磨损的测量结果表明,PCBN刀具高速切削HR-2时,CBN含量高的刀具显示出更长的使用寿命,且在130-200m/min区间为最佳切削速度区域。SEM和EDS分析结果表明,高速精密切削HR-2的磨损机理为氧化磨损、扩散磨损、粘结磨损,同时存在磨粒磨损以及引起的微崩刃现象。     

TiAlN涂层硬质合金刀具车削钛合金螺纹试验

为研究Ti Al N涂层硬质合金刀具车削钛合金螺纹的切削性能,采用Ti Al N涂层硬质合金螺纹刀片进行试验,得出了在进给量2.4mm/r、背吃刀量0.2mm时的最优切削速度为28m/min。在此条件下,验证了刀片前角较小时主切削力小,散热效率高;而前角较大时,切屑螺旋角小且切削长度较长,断屑效果不佳。当进给方向向左时,后刀面的磨损主要是在左后刀面,磨损相对右后刀面严重,较大的后角使得刀片右后刀面磨损宽度小,涂层剥落宽度也小,寿命更长。     

An investigation of tool wear in high-speed turning of AISI 4340 steel

A commercially available insert has been used to turn an AISI 4340 steel at speeds placed between 325 and 1000 m/min. The flank wear was measured in connection to cutting time. This is to determine the tool life defined as the usable time that has elapsed before the flank wear has reached the criterion value.It is shown that an increase in cutting speed causes a higher decrease of the time of the second gradual stage of the wear process. This is due to the thin coat layer which is rapidly peeled off when high-speed turning.The investigation included the realization of a wear model in relation to time and to cutting speed. An empirical model has also been developed for tool life determination in connection with cutting speed.On the basis of the results obtained it is possible to set optimal cutting speed to achieve the maximum tool life.     

Suppression of notch wear of a whisker reinforced ceramic tool in air-jet-assisted high-speed machining of Inconel 718

This paper describes the notch and flank wear specific to a SiC whisker reinforced alumina tool in air jet assisted (AJA) turning of nickel-base superalloy Inconel 718 at high cutting speeds. An AJA machining experiment has revealed that the air jet applied to the tool tip in addition to coolant dramatically reduces the depth-of-cut notch wear. As a result, the width of flank wear, but not the size of notch wear, determined the life of a ceramic tool in AJA machining of Inconel 718. This is a reason for the large extension and small variation of the tool life when high speed AJA machining is adopted. The maximum tool life length reached 2160 m at a cutting speed of 660 m/min under the given cutting conditions. Finally, the mechanisms of the notch and flank wear of a SiC whisker reinforced alumina tool in AJA machining are discussed from the viewpoints of tribochemical reactions and tool wear anisotropy.     

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.