在高速潮湿机械加工条件下后刀面表层磨损机理

1、蹿伏戚澧褐庭蘑速烨谩遢撸贬焱颦睫袅弯逼氢CHAPTER V苋拚鲁跋野浓寇涸佾刺TOOL WEAR MECHANISMS ON THE FLANK SURFACE OF CUTTING INSERTSFOR HIGH SPEED WET MACHINING噱砥颍裙呵厣斑逦啉系5.1 Introduction攮鳢煤蠃存衲敲载趁狭Almost every type of machining such as turning, milling, drilling, grinding., uses a cutting fluid to assist in the cost effective produc

2、tion of parts as set up standard required by the producer 1. Using coolant with some cutting tools material causes severe failure due to the lack of their resistance to thermal shock (like AL2O3 ceramics), used to turn steel. Other cutting tools materials like cubic boron nitride (CBN) can be used w

3、ithout coolant, due to the type of their function. The aim of using CBN is to raise the temperature of the workpice to high so it locally softens and can be easily machined. The reasons behind using cutting fluids can be summarized as follows.疠港希沈帛梢鸵抿郜纬 Extending the cutting tool life achieved by re

4、ducing heat generated and as a result less wear rate is achieved. It will also eliminate the heat from the shear zone and the formed chips.诟缉侵描徙飞嗒碘捣犊 Cooling the work piece of high quality material under operation plays an important role since thermal distortion of the surface and subsurface damage

5、is a result of excessive heat that must be eliminated or largely reduced to produce a high quality product.貉叉穿猸竞岣菘雅尴氍Reducing cutting forces by its lubricating effect at the contact interface region and washing and cleaning the cutting region during machining from small chips. The two main reasons f

6、or using cutting fluids are cooling and lubrication.陛翠汀溯羁华宠挚讨洹Cutting Fluid as a Coolant:秤赠爿裁饿骷凫瞵觎动The fluid characteristics and condition of use determine the coolant action of the cutting fluid, which improves the heat transfer at the shear zone between the cutting edge, work piece, and cutting fl

7、uid. The properties of the coolant in this case must include a high heat capacity to carry away heat and good thermal conductivity to absorb the heat from the cutting region. The water-based coolant emulsion with its excellent high heat capacity is able to reduce tool wear 44.排绰飒酶喻稍实挝敝挹Cutting Fluid

8、 as a Lubricant:箕来趟沫红唪御哓巅饱The purpose is to reduce friction between the cutting edge, rake face and the work piece material or reducing the cutting forces (tangential component). As the friction drops the heat generated is廷枪馋鸩艉煤凄焱趔包dropped. As a result, the cutting tool wear rate is reduced and the

9、surface finish is improved.埤干夭地径峋佧瞎杰怪Cutting Fluid Properties崇莅舜牾故锞妖里蟹掘Free of perceivable odor摆艽驹粜函江茈裰碛残Preserve clarity throughout life媲赵馅沭擂锷贱蚕塌祢Kind and unirritated to skin and eyes.胃皎癔昱爻俪尴尸幢铱Corrosion protection to the machine parts and work piece.糖澳睢忧僚匪傺颔秫撇Cost effective in terms off tool life,

10、 safety, dilution ratio, and fluid life. 1凌錾卅濮梨逝飙鹩珑魉5.1.1 Cutting Fluid Types清讶蝈铆褂舆娄手兑甚There are two major categories of cutting fluids很谎咀车闵佗喊擞舡剐Neat Cutting Oils偶溧诖卟笸槭惯刎敲籽Neat cutting oils are poor in their coolant characteristics but have an excellent lubricity. They are applied by flooding the wo

11、rk area by a pump and re-circulated through a filter, tank and nozzles. This type is not diluted by water, and may contain lubricity and extreme-pressure additives to enhance their cutting performance properties. The usage of this type has been declining for their poor cooling ability, causing fire

12、risk, proven to cause health and safety risk to the operator 1.锿衙乏嘴痖箧马氦郫亦 Water Based or Water Soluble Cutting Fluids酩闱滩焘郦窥队李谋化This group is subdivided into three categories:缕棒缮拖鸢憋憎拗吗琥1. Emulsion mineral soluble white-milky color as a result of emulsion of oil in water. Contain from 40%-80% mineral

13、oil and an emulsifying agent beside corrosion inhibitors, beside biocide to inhibit the bacteria growth.正笤惶暴荭烷薄而婶龄2. Micro emulsion semi-synthetic invented in 1980s, has less oil concentration and/or higher emulsifier ratio 10%-40% oil. Due to the high levels of emulsifier the oil droplet size in th

14、e fluid are smaller which make the fluid more translucent and easy to see the work piece during operation. Other important benefit is in its ability to emulsify any leakage of oil from the machine parts in the cutting fluid, a corrosion inhibitors, and bacteria control.窗蚓雌鹩喝倚汩宫曾蚝3. Mineral oil free

15、synthetic is a mix of chemicals, water, bacteria control, corrosion inhibitors, and dyes. Does not contain any mineral oils, and provides good visibility靥葫涣颃炅枸只岈獯杪爪洛柬嘲轱嗟辩伯用岚.23 to the work piece. bare in mind that the lack of mineral oil in this type of cutting财淄爬荨落蔗俩岗陴俄fluid needs to take more atte

16、ntion to machine parts lubrication since it should not leave an oily film on the machine parts, and might cause seals degradation due the lack of protection.么抄达螗猸澧瞧踉咨鹌5.1.2 Cutting Fluid Selection馁倡去攮淘艉霹瞥珧杼Many factors influence the selection of cutting fluid; mainly work piece material, type of mac

17、hining operation, machine tool parts, paints, and seals. Table 5-1 prepared at the machine tool industry research association 2 provides suggestions on the type of fluid to be used.绰渗宀淮殡煮鼻泠夸暑5.1.3 Coolant Management矛严峨氯匿吐疯煜厕索To achieve a high level of cutting fluids performance and cost effectivenes

18、s, a coolant recycling system should be installed in the factory. This system will reduce the amount of new purchased coolant concentrate and coolant disposable, which will reduce manufacturing cost. It either done by the company itself or be rented out, depends on the budget and management policy o

19、f the company 1. 诘汊渐督铡唉孑识杈嵯Table 5-1 Guide to the selection of cutting fluids for general workshop applications.瓢匍祭岔阵孬愎桔卿所Machining轭客甭棚矬岢樊钋融攫operation裴芏戳妈巩餮血适阔惬Workpiece material镑喂烯芥坷鹘磬擎滁霈掮繇丰充预蛇謦拜肠耵Free machining罱相蜞嗨珐诓姨违赋钕and low -乍锆咽箜槭斧差紫裂盾carbon steels肟蔽贯炼梵蝴惠刈杳殒Medium-帽鼷援属侬籍天髯瀛蟠Carbon steels穆稷绕赭箍湖

20、胨召罨琰High Carbon迷泵餐庇折郑陶劾井蝶and alloy steels咆用泯苓披掌莽故倚窜Stainless and德町镬逾嫒磉鹣酌柳砌heat treated说谥剖矢酝满遨薏翟捋resistant掸桅氖浍烂钉霈莆萁疚alloys把荜噎濂蜗弹徒崛智吡Grinding巳逑镫迨捅左绚求搿大Clear type soluble oil, semi synthetic or chemical grinding fluid枰卢洄缪暨龉镬于噌驳Turning印姆憨虹淅褓绋掼刁缀General purpose, soluble oil, semi字摩啊拍翔憝陵夫浈冷synthetic or sy

21、nthetic fluid悔琊萁俞拐瀑楦庖夭葱Extreme-pressure soluble oil,担伙谧莓驮餮茬愚涉禚semi-synthetic or synthetic聿芗儋崇蔓靶句打蝼胗fluid纪余疏熳遨郾芦踹琬柒Milling镩璎憩饴鞘增笸蔹硭凝General恨鸭刀囝跑倌掮郧阄鬯purpose,逸袁题幻菟磁胪浇榻赐soluble oil,同懿孔脱熹譬擐豫屋偈semi synthetic沧荪呲钪腌颊璎莅锚频or synthetic居腓惺慨戛淘茉鹎耸邕fluid审榍劲舄乡龋锯猷颥啊Extreme-抢鱼蚬挺潴蚯悍御瘭醺pressure soluble柒烙来灵讫口胞稂曰鲠oil, se

22、mi-苘秋犄呢靼锄橘尔劢巡synthetic or纂谲滓澡醍谁奶啤厉箍synthetic fluid校忆篾助橄瘌盆钔溽睛Extreme-pressure soluble oil,泥如龄仉京惨躬搬遍挪semi-synthetic or synthetic椐廷姣刊怠蹁鼷嘉厘嵛fluid(neat cutting oils may be齄麓饩曩灬能洽吒螃麂necessary)茵茌洞碎后蚝余潇蚊窖Drilling杭言擂敦牍秭璨撄疃胸Extreme岫彭勇腋趱速愦骄吃菹pressure soluble奉超群伏蛰筵狙梃袅蟑oil, semi僖呜彻擞链胶齿泉筅苍synthetic or辚崇枘健字停锴距玖腹sy

23、nthetic fluid墚咀试铄盖杀喈猪惭辉艰璁俯支弊墉倔镭磉娲Gear Shapping苟紫疮色抠枷鳐雌朕宛Extreme-pressure soluble oil,肋马捷孢沥筮伍箭胜觫semi-synthetic or synthetic fluid胃鸺揉侯河秋轱馆浒旯Neat-cutting oils preferable比湘显缪菸嗾标踏浠彷Hobbing蒋硭锼冷冕怄蓄颥咎檫Extreme-pressure soluble oil, semi-synthetic or蒺明麓蕨咴芯黾廾钞藐synthetic fluid (neat cutting oils may be preferab

24、le)柠涣脘崤滤掊冱画谑锔Neat-cutting氦贱槁杩果郄涉壳赝肌oils牍嵩垮脞嗄嘹毙锉娑簸preferable鹦恐夥胄芯憎于脎啦蛙Bratching汔举诊屋鸟样穿好豹娴Extreme-pressure soluble oil, semi-synthetic or synthetic fluid (neat碳使奘稠逛髅劾拉呙谯cutting oils may be preferable)蕨苛缅苌镨幔蕞疔晓妹Tapping椒囤铒芘彩霭谏怜庞书Extreme-pressure soluble oil, semi-synthetic or浩学笏雩雇凼颗蹙武喧synthetic fluid(ne

25、at cutting oils may be necessary)獾闷创撅蝙捍八迪阄搬Neat-cutting暾把讵然菌绀娇佴晨礅oils寮嘛多冂睬瑭腿圾壶鸠倏佻斑隋蒜刎侧偶份黑preferable樾劐既蒲榄蛞恢恝馗衅慢赌授忖悴僬耠琦誊喱队锚讧底箅妆启瓞刹龈Note: some entreis deliberately extend over two or more columns, indicating a wide range of possible applications. Other entries are confined to a specific class of work m

26、aterial.武坩镟噶乏忄缔拳抨睛Adopted from Edward and Wright 2鬟注虞绂赀隶雹荟窑柚5.2 Wear Mechanisms Under Wet High Speed Machining垃煽恂峭笄诗赎睿醴尬It is a common belief that coolant usage in metal cutting reduces cutting temperature and extends tools life. However, this research showed that this is not necessarily true to be

27、generalized over cutting inserts materials. Similar research was carried out on different cutting inserts materials and cutting conditions supporting our results. Gu et al 36 have recorded a difference in tool wear mechanisms between dry and wet cutting of C5 milling inserts. Tonshoff et al 44 also

28、exhibited different wear mechanisms on AL2O3/TiC inserts in machining ASTM 5115, when using coolants emulsions compared to dry cutting. In addition, Avila and Abrao 20 experienced difference in wear mechanisms activated at the flank side, when using different coolants in testing AL2O3lTiC tools in m

29、achining AISI4340 steel. The wear mechanisms and the behavior of the cutting inserts studied in this research under wet high speed-machining (WHSM) condition is not fully understood. Therefore, it was the attempt of this research to focus on the contributions in coating development and coating techn

30、iques of newly developed materials in order to upgrade their performance at tough machining conditions. This valuable research provides insight into production timesavings and increase in profitability. Cost reductions are essential in the competitive global economy; thus protecting local markets an

31、d consisting in the search of new ones.德屏篑念顷舶芜避阡磁5.3 Experimental Observations on Wear Mechanisms of Un-Coated Cemented Carbide Cutting Inserts in High Speed Wet Machining颜洚渎庳饣窖池魏铱钥In this section, the observed wear mechanisms are presented of uncoated cemented carbide tool (KC313) in machining ASTM

32、 4140 steel under wet condition. The overall performance of cemented carbide under using emulsion coolant has been improved in terms of extending tool life and reducing machining cost. Different types of wear mechanisms were activated at flank side of cutting inserts as a result of using coolant emu

33、lsion during machining processes. This was due to the effect of coolant in reducing the average temperature of the cutting tool edge and shear zone during machining. As a result abrasive wear was reduced leading longer tool life. The materials of cutting tools behave differently to coolant because o

34、f their varied resistance to thermal shock. The following observations recorded the behavior of cemented carbide during high speed machining under wet cutting.涞牖铥醍戢峁芨颂宿讦Figure 5-1 shows the flank side of cutting inserts used at a cutting speed of 180m/min. The SEM images were recorded after 7 minute

35、s of machining. It shows micro-abrasion wear, which identified by the narrow grooves along the flank side in the direction of metal flow, supported with similar observations documented by Barnes and Pashby 41 in testing through-coolant-drilling inserts of aluminum/SiC metal matrix composite. Since t

36、he cutting edge is the weakest part of the cutting insert geometry, edge fracture started first due to the early non-smooth engagement between the tool and the work piece material. Also, this is due to stress concentrations that might lead to a cohesive failure on the transient filleted flank cuttin

37、g wedge region 51, 52. The same image of micro-adhesion wear can be seen at the side and tool indicated by the half cone浊辊刳呈训韭钥磅淞劫27 shape on the side of cutting tool. To investigate further, a zoom in view was taken at派苑减冈逡蛸铆尻圊the flank side with a magnification of 1000 times and presented in Figur

38、e 5-2A. It shows clear micro-abrasion wear aligned in the direction of metal flow, where the cobalt binder was worn first in a higher wear rate than WC grains which protruded as big spherical droplets. Figure 5-2B provides a zoom-in view that was taken at another location for the same flank side. Th

39、ermal pitting revealed by black spots in different depths and micro-cracks, propagated in multi directions as a result of using coolant. Therefore, theiiial pitting, micro-adhesion and low levels of micro-abrasion activated under wet cutting; while high levels of micro-abrasion wear is activated und

40、er dry cutting (as presented in the previous Chapter).俎趴躺坛孺臼距骆扪川Figure 5-3A was taken for a cutting insert machined at 150mlmin. It shows a typical micro-adhesion wear, where quantities of chip metal were adhered at the flank side temporarily. Kopac 53 exhibited similar finding when testing HSS-TiN

41、drill inserts in drilling SAE1045 steel. This adhered metal would later be plucked away taking grains of WC and binder from cutting inserts material and the process continues. In order to explore other types of wear that might exist, a zoom-in view with magnification of 750 times was taken as shown

42、in Figure5-3B. Figure 5-3B show two forms of wears; firstly, micro-thermal cracks indicated by perpendicular cracks located at the right side of the picture, and supported with similar findings of Deamley and Trent 27. Secondly, micro-abrasion wear at the left side of the image where the WC grains a

43、re to be plucked away after the cobalt binder was severely destroyed by micro-abrasion. Cobalt binders are small grains and WC is the big size grains. The severe distortion of the binder along with the WC grains might be due to the activation of micro-adhesion and micro-abrasion夥象侪角诛睚疋政唼悍轲笱兼菜家祓椭刑赉拓F

44、igure 5-1 SEM image of (KC313) showing micro abrasion and micro-adhesion (wet).窈哈猫鹆呤吵委孽妪蒉阕饔役组暝驳狮摁廛覆 SEM micrographs of (KC313) at 180m/min showing micro-abrasion where cobalt binder was worn first leaving protruded WC spherical droplets (wet).幢纸塞玖盛跗肼沂蒽悦靳舻礼沱烟杯璧羡琮堞(a) SEM micrographs of (KC313) at 180

45、m/min showing thermal pitting (wet).哈荜雹帽嗷肺以兑敉苏Figure 5-2 Magnified views of (KC313) under wet cutting: (a) SEM micrographs of (KC313) at 180mlmin showing micro-abrasion where cobalt binder was worn first leaving protruded WC spherical droplets (wet ), (b) SEM micrographs of (KC313) at 180.m/min show

46、ing thermal pitting (wet ).抚鋈胳勘甜桷濒刊莲朋签陲癌鼎工陵戴赘帙焕 SEM image showing micro-adhesion wear mechanism under 150m/min (wet).淝江雀独旬幂释熵嘛又捆狻艘氘螈许兢岽樟苌(a) SEM image showing micro-thermal cracks, and micro-abrasion.岬掰脓杞蔺仿凇岈燠遍Figure 5-3 Magnified views of (KC313) at 150m/min (wet): (a) SEM image showing micro-adhes

47、ion wear mechanism under 150m/min (wet), (b) SEM image showing micro-fatigue cracks, and micro-abrasion (wet).脓缅协惩艉赙碱坂驭簟Wear at the time of cutting conditions of speed and coolant introduction. Therefore, micro-fatigue, micro-abrasion, and micro-adhesion wear mechanisms are activated under wet condi

48、tion, while high levels of micro-abrasion were observed under dry one.眼映献啧丈镯凋讹频荼Next, Figure 5-4A was taken at the next lower speed (120m/min). It shows build up edge (BUE) that has sustained its existence throughout the life of the cutting tool, similar to Huang 13, Gu et al 36 and Venkatsh et al 5

49、5. This BUE has protected the tool edge and extended its life. Under dry cutting BUE has appeared at lower speeds (90 and 60 m/min), but when introducing coolant BUE started to develop at higher speeds, This is due to the drop in shear zone temperature that affected the chip metal flow over the cutt

50、ing tool edge, by reducing the ductility to a level higher than the one existing at dry condition cutting. As a result, chip metal starts accumulating easier at the interface between metal chip flow, cutting tool edge and crater surface to form a BUE. In addition to BUE formation, micro-abrasion wea

51、r was activated at this speed indicated by narrow grooves.胼砘卸稻脞嶂皲域蜃桓To explore the possibility of other wear mechanisms a zoom-in view with a magnification of 3500 times was taken and shown in Figure 5-4B. Micro- fatigue is evident by propagated cracks in the image similar to Deamley and Trent 27 fi

52、nding. Furthermore, Figure 5-4B shows indications of micro-abrasion wear, revealed by the abrasion of cobalt binder and the remains of big protruded WC grains. However, the micro-abrasion appeared at this speed of 120m/min is less severe than the same type of micro-wear observed at 150 m/min speed,

53、supported with Barnes 41 similar findings. Therefore, micro-abrasion, BUE and micro-fatigue were activated under wet condition while, adhesion, high levels micro-abrasion, and no BUE were under dry cutting.卺筠檑磲軎偃焦屏脲勖 SEM image of (KC313) showing build up edge under 120m/min (wet).衮犀僳痛杜孳点餍捂偏滟盎迸晾嗲舷槭咿囔

54、崖(a) SEM image of (KC3 13) showing micro-fatigue, and micro-abrasion (wet).褙鲕房诜孺璋噢猴摞跑Figure 5-4 SEM images of (KC313) at 120m/min (wet), (a) SEM image of (KC313). showing build up edge, (b) SEM image of (KC313) showing micro-fatigue and micro-abrasion染泌蠕锗荽瀛霎哥囟裁33 Figure 5-5 is for a cutting tool mac

55、hined at 90m/min, that presents a good妯悸常耍硖江第蹰白恨capture of one stage of tool life after the BUE has been plucked away. The bottom part of the flank side shows massive metal adhesion from the work piece material. The upper part of the figure at the edge shows edge fracture. To stand over the reason o

56、f edge fracture, the zoom-in view with magnification of 2000 times is presented in Figure 5-6A. The micro-fatigue crack image can be seen as well as micro-attrition revealed by numerous holes, and supported with Lim et al 31 observations on HSS-TiN inserts. As a result of BUE fracture from the cutti

57、ng tool edge, small quantities from the cutting tool material is plucked away leaving behind numerous holes. Figure 5-6B is another zoom-in view of the upper part of flank side with a magnification of 1000 times and shows micro-abrasion wear indicated by the narrow grooves. Furthermore, the exact ty

58、pe of micro-wear mechanism appeared at the flank side under 60 m/min. Therefore, in comparison with dry cutting at the cutting speed of 90 m/min and 60 m/min, less micro-abrasion, bigger BUE formation, and higher micro-attrition rate were activated. 卧郭姐咭攫跽烟席涯济理雇鼹奸舨棰臀佯楂氐Figure 5-5 SEM image showing tool edge after buildup edge was plucked away. 榉辋六遵淮彝桃傩贤稍忄隙舀肺杆砭钵蜴圾举SEM image showing micro-fatigue crack, and micro-attrition.廒椎寸蝻胄槐郜诀阃情勘廷岸倬赢甑眇扁尺瘠(a) SEM image showing micro-abrasion.袄缃浣黢赏矢恹谠蹈笪Figure 5-6 SEM images of (KC313) at 90m/min:(a) SEM image showing micro-fatigue crack, and