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中英文 翻译 ALSiC 颗粒 金属 复合材料 加工

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中英文翻译-ALSiC颗粒金属基复合材料的加工,中英文,翻译,ALSiC,颗粒,金属,复合材料,加工

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AL/SiC颗粒金属基复合材料的加工摘要尽管金属基复合材料颗粒具有优越的机械性能和热性能，但是有限的切削性却一直使金属部件的替代受到很大的威慑。在加工过程中，增强硬磨料的相时会导致加工工具的快速磨损，因此，会产生较高的加工费用。一系列高速转动测试只为选择最佳刀具材料，刀具几何形状和切削参数来车削含有20%的SiC/AL金属基复合材料。结果表明,多晶金刚石工具（PCD）与氧化铝和涂层硬质合金工具相比，可以提供给用户满意的刀具寿命。其中在金属基复合材料的加工下研究过程中，后面一种材料的工具更容易受到过度的边缘碎屑和月牙洼磨损。此外，PCD刀具的成本可通过在干切削进给量f=0.45mm，切割速度V=894 m/s与切削深度为1.5毫米时被鉴别。与这些切削参数类似, 在刀具上形成相对较小的累积起来边缘，会很好的保护它免受进一步边缘上工具的磨损和磨损。具有零度前角和较大刀具半径的多晶硅刀具大多被用于粗加工。关键词：金属基复合材料，刀具磨损1 简介 一组新形式的金属基复合材料（MMCs）已受到大量的研究，因为在20世纪80年代早期的试验工程材料中，最流行的材料为硅，碳化硅，氧化铝，铝，钛，磁性地层，其中钛和镁合金是常用的基体相。大多数金属复合材料密度约为三分之一。在钢铁行业，由于这些潜在高强度和刚度吸引力再加上在高温无法工作的性能，导致金属基复合材料竞争非常严峻。在航空航天和汽车应用中，高温合金，陶瓷，塑料被重新设计的钢件。后者中的材料，操作方法比以往任何时候都不可能有太多的进步，今后仍然不可避免。 有人对金属基复合材料微粒（PMMCs）特别感兴趣，不只是因为他们表现出较高的延性和金属基复合材料向异性。此外，PMMs提供了卓越的耐磨性。虽然许多工程元件制成PMMCs是由形状近乎成形和精进的铸造工艺，但是他们需要这些系列，其中荷兰国际集团达到了预期的尺寸和表面光洁度。PMMCs加工提出了重大挑战，因为加固材料的数量明显比常用高速钢（HSS）和硬质合金工具更难。因此，钢筋相磨具磨损快的原因，普遍是因为使用的PMMCs，其明显阻碍其加工性和高加工成本。文献综述从现有文献上很明显看出PMMCs的性能，密度（克立方厘米） 2.77热导率（卡尔厘米秒K在22C 0.47比热（卡尔克k） 100 0.218 200 0.239 300 0.259平均热膨胀系数 50100 17.5 50300 21.1 50500 21.4极限强度 （） 262屈服强度（） 21.4伸长率（） 1.9弹性模量（GPA） 98.6洛氏硬度（B） 671.5表1典型的 F3S.20S物理性能特性的形态，分布和数量的增强相分数，以及矩阵的性质，都是影响因素，整体切割工艺相对较少，但尚未涉及到工程的生产力的工艺优化。例如，莫纳亨研究在加入25碳化硅和铝硬质合金刀具的磨损机理。PMMC在速度低于20米每分钟时的加工速度开发了一种工具寿命的关系，为硬质合金刀具加工过程中碳化硅和铝PMMCs在速度低于每分钟100米时。然而，文献的作者建议的内置式边现象，是在观察期间碳化硅加工进一步研究铝PMMCs。Reillyet等排名刀具磨损方面的各种刀具材料，然而，他们的切削用量不超过每分钟125米和f=1.0mm，这是取得使用立方氮化硼工具。类似测试结果报告了布伦等在有关刀具的磨损率，主要是由于磨损涉及到刀具的硬度。 Winery归因于碳化物耐磨工具，打磨表面上形成氧化铝颗粒擦在芯片的流动方向的工具。不过，拉伸颗粒也有可能导致同样的效果，碳化硅颗粒硬度大于WC。托马茨认为少于氧化铝和碳化硅的硬度涂层提供碳化硅加工过程中几乎没有任何优势：铝PMMCs。布伦提出使用较低的切削速度，减少切削温度，从而加速扩散和粘着磨损和热削弱工具。由于铝的工具面和晶界自扣押的地点，作者建议使用硬质合金工具与大的晶粒尺寸。 一些研究者表明，多晶金刚石（PCD）的工具是唯一的工具伴侣-里亚尔，它是提供一个有用的工具，能够生活在铝PMMCs在的加工。 PCD是难比Al2O3和和不产生化学反应倾向与工件材料。托马茨比较了化学气相沉积法（CVD）插入到锡，钛（CN）和氧化铝涂层刀具的性能。化学气相沉积工具提供更好的整体比其他工具的性能。 Lane 研究了不同的心血管疾病的工具，薄，厚的薄膜的性能。根据他们的观察，化学气相沉积薄膜的工具与失败在这20碳化硅端铣灾难性的铝PMMC。这个工具的失败是由于涂层剥落和由此产生的损坏年龄相对软硬质合金衬底。此外，具有较好的晶粒尺寸25毫米PCD刀具磨损微承受比为10毫米晶粒尺寸切割工具的磨损。在聚晶金刚石晶粒尺寸进一步增加不利于刀具寿命，而导致在表面光洁度显着恶化。 表三 刀具材料对切削力和温度影响 (r=1.6mm; =0)刀具材料 测量切削力 (N) 测量切削温度 (C)PCD (v=894 m min-; 97.00 440F=0.45 mm rev-;doc=2.5 mm)PCD (v=670 m min-; 98.10 410f=0.25 mm rev-;Doc=1.5 mm)Al2O3(v=248 m min-; 183.85 520 f=0.2 mm rev-; Doc=0.5 mm) TiN (6248 m min-; 143.52 500f=0.2 mm rev-; Doc=0.5 mm这是因为晶粒尺寸的PCD材料的刀具在25毫米很容易退出了边缘。相对于切削参数对刀具寿命等影响减少了。主要归因于对PCD刀具的磨损（由磨损）在防皱到在所获得的动能增加碳化硅颗粒磨。另一方面，布伦等由于在刀具磨损中的热降解增加刀具材料。刀具磨损被认为与车削材料成反比。托马茨等把刀具寿命归因于在更高的进给量增加了复合材料的热软化。作者认为，工件材料变得柔软和颗粒成为压入工件，造成工具本身磨损少。然而,莫林认为由于以更大的进给量减少对刀具前沿的磨损，磨料碳化硅颗粒减少接触。尽管在解释背后的不同进给量工具磨损机理的争论，所有的研究人员建议使用切割进给速度和进给量是在粗加工尽可能咄咄逼人。最后，关于冷却液的应用，在美国科学家建议以便对于可能采取的保护优势建成边缘现象。 总之，进行文献回顾显示，更积极的（速度，进给量和切削深度）切削参数的影响还需要进一步重新搜索，以改善切削过程的经济性。此外，一些重要参数进行了前人所忽略，其中有刀具几何形状和冷却剂的应用。2 试验材料和切割工具2.1工件材料 该加工利用Duralcan进行了调查 F3S.20S铝：碳化硅金属基复合材料。有一对颗粒平均直径为12毫米。表1显示了对A356- 20的PMMC的物理力学性能一些。在此之前进行切割实验，测试材料是完全热处理对T71条件。测试材料是在对一百七十七点八毫米直径305毫米的长度形式。2.2 切削工具 各种刀具材料（涂层硬质合金，氧化铝）和几何结构，在Oblique对于转向就业进行了测试和不同的切削参数，每个工具伴侣-里亚尔就业。然而，对于比较刀具磨损的目的，所有的切削试验共进行了拆除金属固定量（300立方毫米）。表2总结了刀具数据在干车削试验，进行了10种惠普标准的现代化数控车床。切削力康具磨损测量康廷每个切削参数组合。该工具的力量测定采用一奇石三分量测力计和切削条件选择精心为每个工具材料。一些在切削实验中，测量采用K型工具到被粘热电偶刀具离前沿1毫米时的温度。测量的技术可靠性检查，不断重复的实验和各组的结果表明，如果在他们展出了不到5的变异。在每个切削试验结束时，刀具磨损进行了检查用扫描电子显微范围和X射线分散技术。该工具后刀面磨损（VB）的测定用工具显微镜。 3 结果与讨论3.1 刀具材料的影响 一个初步的测试并进行一系列对刀具磨损的影响刀具材料，切削部分和切削温度在粗糙投票荷兰国际集团20的碳化硅和铝PMMC。图1可以看出，氧化铝TiC的工具遭受的EDGE芯片形式的过度磨损水平。氧化铝颗粒的研磨拔出工件颗粒，其中有一个更大的硬内斯号（VHN间接），比氧化铝颗粒（VHN在Al2O3TiC 2500公斤力每平方毫米; VHN在碳化硅3000公斤力每平方毫米）。月牙磨损也观察到，这是由于该是由磨损造成的沟槽扩大。由于严重的边缘切削，Al2O3TiC切削力的工具明显比实验更高氮化钛（见表3）涂层刀具。氮化钛涂层规定对磨料的影响，一些保障SiC颗粒。聚优越的性能金刚石工具，相比，无论氧化铝：TiC的和TiN涂层硬质合金工具，是由于他们的高耐磨性和高导热性，这导致了更低的切削温度，如图表3。因此，所有的可加工性进行的研究其后关注到的最优化PCD刀具切削过程中使用。3.2 切削参数的影响图2和3表明，随着切削速度对切屑的增加，减少切削力深度。这可能是归因于热软化工件材料。另一个可能的原因是由于引入到刀具几何形状的变化后，形成建成的边缘。图4（b）给出了透视内置的注册材料色散图所示4（a）条。图6（a）内置式边对PCD工具（v= 670 m/min，f=0.35mm/rev，doc=1.5mm，r=1.6毫米，=0）,图 (b)相当于 6（a）项，只是doc= 2.5mm图7（a）SEM照片说明上的PCD刀具前刀面磨损溶解后用氢氧化钠积屑瘤（v=670 mmin-1，f=0.15mm，doc= 1.5mm，=1.6mm，a=0。C）图 8切割对刀具NK细胞的磨损（PCD刀具速度：r=1.6毫米，a=0。C;广角点：V=670 m.min-1,doc=1.5mm,;轮点：v=894 m.min-1，doc=1.5mm）。图9影响对工具NK细胞的磨损（PCD刀具切削深度：=1.6mm，a=；v=894 m ;方点：doc=1.5mm轮点：doc=2.5mm）。建成边缘，观察到的所有工具在所有切削条件。这是因为颗粒碳化硅：铝金属基复合材料有材料的特性所有（即应变硬化两相材料在高温和压力）。在高切削速度（图5（b），一个较小的积屑瘤形成，比积屑瘤形成（图5（a）的积屑瘤的高度测量前刀面垂直）在对比度，通过增加从1.5到2.4毫米的切削深度，大积屑瘤形成（图6（a，b）项，这可能中断造成的工具和由此产生的切削工具对工件表面粗糙度和不利影响尺寸精度。该工具的拓扑图显示，主要磨损PCD的机制是磨损（如凹槽表现平行于芯片水流方向）。这些沟槽可以归因于三个因素。第一，氧化铝是形成于边缘的工具，这是很难足以开槽的金刚石生产磨损。第二为国家的PCD槽为铝扣押和拉出来的金刚石颗粒的过程中，如图所示7（甲，乙）。第三个可能的原因背后的PCD槽是sic颗粒研磨的工具。因此，PCD刀具与金刚石颗粒比碳化硅晶粒尺寸较大粒子可以更好地抵御磨损和密CRO的切割的碳化硅颗粒。然而，我们应请注意，由于增加的PCD颗粒的大小，PCD刀具的断裂特性恶化，因在材料中的一个缺陷增加。认为是对的工具面形成凹槽充满了工件材料。这秉承层有些保护，以防止进一步的工具的前刀面磨损。尽管如此，该工具后刀面继续受到磨损。因此，后刀面磨损（VB）的是作为刀具寿命准则与V=0.18毫米。图8显示，随着切削速度的增加，后刀面磨损增加。这可能是由于增加在研磨粒子的动能，正如先前推测的巷17。切深增加导致在增加后刀面磨损（图9）。这是由于增强微磨损，在切削刀具后刀面。这在一个更深入的情况下切点，该工具后刀面较大的表面面积接触磨损。进给速度提高了有益的影响。随着在图所示。 8和9的进给速度的增加，该刀具磨损减少。在高进给量情况下，固定体积的金属切削，刀具表面会有较少的磨料PMMC接触。另一个优势获得了通过提高进给速度为改变芯片的形式。在低进给率，该芯片形成了连续的，也被困难和灾害的处理。在高进给速度和高深度切（f=0.35mm，doc= 2.0mm），形成了芯片不连续的。尽管在所有的实验PCD刀具具有高进给量较低，导致工具磨损，对最佳切削明确的决定参数应考虑的影响表面上的完整性和切削参数亚表面损伤产生的工件，分析表面完整性和芯片形态将在第二部分介绍本研究性学习。 10 a-b-c 图 11 a-b图10（a）对PCD刀具前角的刀具NK细胞的磨损（v=894m/min，doc=2.5mm，r=1.6mm;a=0。C;）（b）对PCD刀具前角对的切削力（v= 894 m/min，doc=2.5mm）（c）扫描电镜图像说明由腐蚀PCD刀具磨损。图11（a）SEM图，说明了PCD刀具磨损的切削（v= 894 m/min，doc=1.5mm，v=0.35mm_1，r=0.8mm，a=0。C）（b）影响刀尖半径对工具铿俛NK细胞的磨损（v= 894mm/min，doc=2.5mm，a=0。C;工具：方点，r=1.6mm;轮间距点，r=0.8mm）。3.3 刀具几何形状的影响在刀具前角对的深远影响PCD刀具的磨损。三种不同的角度进行靶检查。正如从10（a）图中可以看出工具类倾斜角度出发，进行积极的和负面的靶角工具。为增加负前角后刀面磨损情况下可能的原因，是更大的切削力遇到这样的前角（图10（b）项）。此外，该芯片生产成为捕获之间的工具和工件，造成损害该工具的表面。正前角与工具显示不规则的后刀面磨损和过度的切割点蚀边缘地带，如图所示。 10（c）项。刀尖半径在决定了关键作用该工具的磨损模式。由于刀尖半径从1.6至0.8毫米，该工具被发现遭受过度切削和月牙磨损，作为如图所示。 11（a）条。这导致了切削工具在切削力和后刀面磨损增加，如图11（b）项。半径小工具因此建议的在穷为轻切削精加工业务使用参数。小鼻子半径也将以产生更好的几何精度。4 结论（1）的主要工具是磨损，磨损机理微切削刀具材料晶粒，表现为在刀具面平行沟槽到芯片流方向。所有的工具都进行测试也因后刀面损，由于磨损。没有证据化学磨损（例如，通过扩散）。（2）PCD刀具磨损持续最少的COM削减到TiN涂层硬质合金刀具和氧化铝：TiC的工具。这无疑是由于金刚石的硬度优和耐磨性，以及低摩擦系数，加上高导热。这导致PCD刀具时，降低了切削温度就业。另一方面，锡涂层硬质合金工具和Al2O3/TiC的工具遭受过度火山口边缘的磨损和剥落。（3）对PCD的前刀面形成的沟槽涂抹工具，充满了工件材料。这内置式形式是有利的，因为它保护刀具前进一步磨损。（4）在确定切削参数发挥了关键作用，采矿刀具后刀面磨损量，以及大小建成的边缘。工具磨损降至最低提高进给速度，这导致了减少接触的工具和SiC颗粒打磨。虽然提高铝切割速度，预计到加速度，中心提供全方位的侧面磨耗显着，其结果表示，最小的磨损增加。高等教育切割速度均与在增加切削温度，而导致形成一个保护坚持一层薄薄的工件材料上该工具。这种保护建成边缘形式无法在规模增长的摩擦增加的速度。切削参数范围内的测试范围，在894 m最小速度，f= 0.45毫米和切削深度d=1.5毫米的结果是最小的工具磨损。这些切削参数提高用PCD刀具时。（5）PCD刀具半径与鼻子16毫米和仰角a=0 也导致了较低的后刀面磨损。致谢笔者要感谢来自美国Duralcan的R.Bruski和来自GE超硬材料D.Dyer，他们提供了试验材料，切割工具和整个研究项目的有益意见。在实验进行加工智能机械及制造麦克马斯特大学的研究中心。（1）的主要工具是磨损，磨损机理微切削刀具材料晶粒，表现为在工具面平行沟槽到芯片流方向。所有的工具都进行测试也因后刀面磨损，由于磨损。没有证据化学磨损（例如，通过扩散）。（2）PCD刀具磨损持续最少的COM削减到TiN涂层硬质合金刀具和氧化铝：TiC的工具。这无疑是由于金刚石的硬度优和耐磨性，以及低摩擦系数，加上高导热。这导致PCD刀具时，降低了切削温度就业。另一方面，锡涂层硬质合金工具和Al2O3/TiC的工具遭受过度火山口边缘的磨损和剥落。（3）对PCD的前刀面形成的沟槽涂抹工具，充满了工件材料。这内置式边形式是有利的，因为它保护刀具前进一步磨损。（4）在确定切削参数发挥了关键作用，开采的工具NK细胞的磨损量，以及大小建成的边缘。工具磨损降至最低提高进给速度，这导致了减少接触的工具和SiC颗粒打磨。铝虽然提高切割速度，预计到加速度，中心提供全方位的NK细胞磨料磨损厉害，结果表示，最小的磨损增加。高等教育切割速度均与在增加切削温度，而导致形成伸出工件材料薄层上该工具。这种建成边形式无法在规模增长的摩擦增加的速度。切削参数范围内的测试范围，在1894 m最小速度，女0.45毫米转1和切削深度1.5毫米，导致在最小的工具磨损。这些切削参数提高PCD刀具的利用率。（5）PCD刀具半径16毫米的仰角0度也导致了较低NK细胞的磨损。Journal of Materials Processing Technology 83 (1998) 151158Machining of Al/SiC particulate metal-matrix compositesPart I: Tool performanceM. El-Gallaba, M. Skladb,*aPratt and Whitney Canada, Mississauga, Ontario, L5T1J3, CanadabDepartment of Mechanical Engineering, McMaster Uni6ersity, Hamilton, Ontario, L8S4L7, CanadaReceived 20 March 1997AbstractDespite the superior mechanical and thermal properties of particulate metal-matrix composites, their poor machinability hasbeen the main deterrent to their substitution for metal parts. The hard abrasive reinforcement phase causes rapid tool wear duringmachining and, consequently, high machining costs. A series of dry high-speed turning tests were performed to select the optimumtool material, tool geometry and cutting parameters for the turning of 20%SiC/Al metal-matrix composites. The results indicatethat polycrystalline diamond tools (PCD) provide satisfactory tool life compared to alumina and coated-carbide tools, where thelatter tools suffered from excessive edge chipping and crater wear during the machining of the metal-matrix composite understudy. Furthermore, the cost of PCD tools could be justified by using dry cutting at feed rates as high as 0.45 mm rev1, cuttingspeeds of 894 m min1and a depth of cut of 1.5 mm. With these cutting parameters, the relatively small built-up edge formedon the tool protects it from further wear by abrasion and micro-cutting. Polycrystalline tools with zero rake angle and large toolnose radii are recommended for the roughing operations. 1998 Elsevier Science S.A. All rights reserved.Keywords:Metal-matrix composites; Tool wear1. IntroductionMetal-matrix composites (MMCs) form one group ofthe new engineered materials that have received consid-erable research since the trials by Toyota in the early1980s 1. The most popular reinforcements are siliconcarbide and alumina. Aluminium, titanium and magne-sium alloys are commonly used as the matrix phase.The density of most MMCs is approximately one thirdthat of steel, resulting in high specific strength andstiffness 2. Due to these potentially attractive proper-ties coupled with the inability to operate at high tem-peratures, MMCs compete with super-alloys, ceramics,plastics and re-designed steel parts in several aerospaceand automotive applications. The latter materials, how-ever, may not have much further capacity for theinevitable future increases in service loads 3.Particulate metal-matrix composites (PMMCs) are ofparticular interest, since they exhibit higher ductilityand lower anisotropy than fiber reinforced MMCs 2.Moreover, PMMCs offer superior wear resistance 3.WhilemanyengineeringcomponentsmadefromPMMCs are produced by the near net shape formingand casting processes, they frequently require machin-ing to achieve the desired dimensions and surface finish.The machining of PMMCs presents a significant chal-lenge, since a number of reinforcement materials aresignificantly harder than the commonly used high-speedsteel (HSS) and carbide tools 4. The reinforcementphase causes rapid abrasive tool wear and therefore thewidespread usage of PMMCs is significantly impededby their poor machinability and high machining costs.2. Literature reviewFrom the available literature on PMMCs, it is clear* Corresponding author. Fax: +1 905 5727944; e-mail: mech-macmcmaster.ca0924-0136/98/$19.00 1998 Elsevier Science S.A. All rights reserved.PIIS0924-0136(98)00054-5M. El-Gallab, M. Sklad/Journal of Materials Processing Technology83 (1998) 151158152Table 1Typical physical properties of Duralcan F3S.20S 20PropertyDensity (g cm3)2.77Thermal conductivity (cal cm1s1K1) at 22C0.47Specific heat (cal g1K)0.218100C0.239200C0.259300CAverage coefficient of thermal expansion17.550100C50300C21.121.450500CUltimate strength (MPa)262Yield strength (MPa)21.41.9Elongation (%)98.6Elastic modulus (GPa)6791.5Rockwell hardness (B)Table 2Tool geometryToolGeometryPCD (tipped-80rhomboid)Rake angle, a: 5, 0, 5Clearance angle: 7Approach angle: 5Tool nose radius (mm), r: 0.8, 1.6TiN coated carbideRake angle, a: 0(triangular)Clearance angle: 7Approach angle: 5Tool nose radius (mm), r: 1.6Rake angle, a: 0Al2O3/TiC ceramic(triangular)Clearance angle: 7Approach angle: 5Tool nose radius (mm), r: 1.6crystalline diamond (PCD) tools are the only tool mate-rial that is capable of providing a useful tool life duringthe machining of SiC/Al PMMCs. PCD is harder thanAl2O3and SiC and does not have a chemical tendencyto react with the workpiece material. Tomac et al. 5compared the performance of chemical vapor deposi-tion (CVD) inserts to that of TiN, Ti(CN) and Al2O3coated tools. CVD tools offered better overall perfor-mance than that of the other tools. Lane et al. 18studied the performance of different CVD tools withthin and thick films. According to their observations,CVD tools with thin films failed catastrophically duringthe end milling of 20%SiC/Al PMMC. This tool failurewas attributed to coating spalling and consequent dam-age to the relatively soft carbide substrate. Further-more, PCD tools with a grain size of 25 mm betterwithstand abrasion wear by micro-cutting than toolswith a grain size of 10 mm 8,14. Further increases inPCD grain size do not benefit the tool life, but rathercause significant deterioration in the surface finish. Thisthat the morphology, distribution and volume fractionof the reinforcement phase, as well as the matrix prop-erties, are all factors that affect the overall cuttingprocess 2,4, but as yet relatively few works related tothe optimization of the productivity process have beenpulished. For example, Monaghan 2 studied the wearmechanism of carbide tools during the machining of25% SiC/Al PMMC at speeds below 20 m min1.Tomac et al. 5 developed a tool life relationship forcarbide tools during the machining of SiC/Al PMMCsat speeds lower than 100 m min1. However, theauthors of Ref. 5 recommended further research onthe built-up edge phenomenon that is observed in alltools during the machining of SiC/Al PMMCs. OReillyet al. 6 ranked various tool materials with respect totool wear, however, their cutting parameters did notexceed 125 m min1and 1.0 mm depth of cut, whichwas achieved using cubic boron nitride tools. Similartest results were reported by Brun et al. 7 who relatedthe tool wear rate, mainly due to abrasion, to the toolhardness. Winert 8 attributed the wear of the carbidetools to abrading Al2O3particles that form on thesurface and rub the tool in the direction of the chipflow. However, pulled SiC particles could also lead tothe same effect, SiC particles also being harder than theWC. Tomac et al. 5 suggested that coatings with lesshardness than that of Al2O3and SiC offer little to noadvantage during the machining of SiC/Al PMMCs,Brun et al. 7 suggested using lower cutting speeds toreduce the cutting temperature, which accelerate diffu-sion and adhesion wear and thermally weaken the tool.Since aluminium tends to seize on the tool face andsince grain boundaries are the sites of seizure, theauthors recommended using cemented carbide toolswith a large grain size.Several researchers 725 have indicated that poly-Fig. 1. SEM figure showing wear on Al2O3tool (6=488 m min1,f=0.2 mm rev1, doc=0.5 mm, r=1.6 mm, a=0).M. El-Gallab, M. Sklad/Journal of Materials Processing Technology83 (1998) 151158153Table 3Effect of tool material on cutting forces and temperatures (r=1.6mm; a=0)Measured cut-Tool materialMeasured cuttingtemperature (C)ting force (N)PCD (6=894 m min1;97.00440f=0.45 mm rev1;doc=2.5 mm)98.10PCD (6=670 m min1;410f=0.25 mm rev1;doc=1.5 mm)520Al2O3(6=248 m min1;183.85f=0.2 mm rev1;doc=0.5 mm)143.52500TiN (6=248 m min1;f=0.2 mm rev1;doc=0.5 mm)Fig. 3. Effect of depth of cut on the cutting forces (PCD tool: r=1.6mm, a=0; square points: 6=894 m min1, doc=1.5 mm; roundpoints: 6=894 m min1, doc=2.5 mm).of cut that are as aggressive as possible during theroughing operations. Finally, with regard to the coolantapplication, researchers at Duralcan USA 1123, rec-ommend investigating the possibility of dry-rough ma-chining in order to take advantage of the protectivebuilt-up edge phenomenon.In summary, the literature review carried out showedthat the effect of more aggressive cutting parameters(speed, feed and depth of cut) still needs further re-search in order to improve the economics of the cuttingprocess. Also, several important parameters have beenoverlooked by previous researchers, among which arethe tool geometry and coolant application.3. Test material and cutting tools3.1.Workpiece materialThe machining investigations were carried out usingDuralcan F3S.20S Al/SiC metal-matrix composite. TheSiC particles had an average diameter of 12 mm. Table1 shows some of the physical and mechanical propertiesof A356-20%SiC PMMC. Prior to carrying out thecutting experiments, the test material was fully heat-treated to the T71 condition. The test material was inthe form of bars of 177.8 mm diameter and 305 mmlength.3.2.Cutting toolsVarious tool materials (coated carbide, Al2O3/TiCand PCD) and geometries were employed in the study.Oblique turning tests were carried out and differentcutting parameters were employed for each tool mate-rial. However, for the purpose of comparing tool wear,all cutting tests were carried out at a fixed volume ofmetal removed (300 mm3). Table 2 summarizes the tooldata.is because PCD grains with size 25 mm are easilypulled out of the cutting edge.Regarding the effect of the cutting parameters on thetool life, Lane et al. 1115,1719 attributed the in-crease in the wear of PCD tools (by abrasion) toincrease in kinetic energy gained by abrading SiC parti-cles. On the other hand, Brun et al. 7 attributed theincrease in tool wear in the thermal degradation of thetool material. Tool wear was found to be inverselyproportional to the feed rate 9. Tomac et al. 5attributed the increase in tool life at higher feed rates tothe thermal softening of the composite. The authorssuggest that the workpiece material becomes softer andthe SiC particles become pressed into the workpiece,causing less abrasion on the tool itself. However, Finnet al. 24 and Morin et al. 25 attributed the reductionin tool wear with greater feed rates to the reducedcontact between the cutting edge and the abrasive SiCparticles. Despite the controversy in explaining themechanism behind the tool wear at different feed rates,all researchers recommend using feed rates and depthsFig. 2. Effect of cutting speed on the cutting forces (PCD tool: r=1.6mm, a=0; square points: 6=670 m min1, doc=1.5 mm; roundpoints: 6=894 m min1, doc=1.5 mm).M. El-Gallab, M. Sklad/Journal of Materials Processing Technology83 (1998) 151158154Dry turning tests were carried out on a 10 HPStandard Modern NC lathe. The cutting force compo-nents (Fx, Fy, Fz) and tool wear were measured contin-uously for each combination of cutting parameters. Thetool forces were measured using a Kistler 3-componentdynamometer and the cutting conditions were selectedcarefully for each tool material. In some of the cuttingtests, the tool temperature was measured using K-typethermocouples that were glued onto the tool rake face,1 mm away from the cutting edge. The reliability of themeasurement techniques was checked constantly byrepeating the experiments and the results of each set ofexperiments were accepted if they exhibited a varianceof less than 5%. At the end of each cutting test, the toolwear was examined using a scanning electron micro-scope and the X-ray dispersion technique. The toolFig. 5. (a) Built-up edge on PCD tools (6=670 m min1, f=0.45mm rev1; doc=2.5 mm, r=1.6 mm); (b) as for Fig. 5(a), but for6=894 m min1.Fig. 4. (a) Built-up edge on PCD tools (6=670 m min1, f=0.25mm rev1, doc=2.5 mm, r=1.6 mm, a=0); (b) X-ray dispersionof built-up edge shown in Fig. 4(a).flank wear (VB) was measured using a toolmakersmicroscope.4. Results and discussion4.1.Effect of tool materialA series of preliminary tests was conducted to assesthe effect of tool material on the tool wear, cuttingforces and cutting temperature during the rough turn-ing of 20%SiC/Al PMMC. Fig. 1 shows that Al2O3/TiCtools suffered excessive wear in the form of edge chip-ping. Al2O3particles are pulled out by the abradingworkpiece particles, which have a greater Vickers hard-ness number (VHN) than the Al2O3particles (VHN forAl2O3TiC=2500 kgfmm2; VHN for SiC=3000 kgfmm2). Crater wear was also observed, which is due tothe widening of grooves that were caused by abrasion.Due to severe edge chipping, the cutting forces for theM. El-Gallab, M. Sklad/Journal of Materials Processing Technology83 (1998) 151158155Al2O3/TiC tool were much higher than those experi-enced by TiN coated tools (Table 3). The TiN coatingprovided some protection against the abrasive effects ofthe SiC particles. The superior performance of poly-crystalline diamond tools, compared to both Al2O3/TiCand TiN coated carbide tools, is attributed to their highabrasion resistance and high thermal conductivity,which led to lower cutting temperatures, as shown inTable 3. Therefore, all machinability studies carried outthereafter were concerned with the optimization of thecutting process using PCD tools.4.2.Effect of cutting parametersFigs. 2 and 3 show that as the cutting speed and/orthe depth of cut increase, the cutting forces decrease.This could be attributed to thermal softening of theworkpiece material. Another possible reason is due tothe changes introduced into the tool geometry upon theformation of built-up edge. Fig. 4(b) shows the X-raydispersion of the built-up material shown in Fig. 4(a).Fig. 7. (a) SEM image illustrating the wear on the PCD tool rake faceafter dissolving the BUE with NaOH (6=670 m min1, f=0.15 mmrev1, doc=1.5 mm, r=1.6 mm, a=0); (b) higher magnification ofrake face of the tool shown in Fig. 7(a).Fig. 6. (a) Built-up edge on PCD tools (6=670 m min1, f=0.35mm rev1, doc=1.5 mm, r=1.6 mm, a=0); (b) as for Fig. 6(a),but for doc=2.5 mm.Built-up edge was observed in all tools under all cuttingconditions. This is because particulate SiC/Al MMCshave all of the characteristics of materials that formFig. 8. Effect of cutting speed on the tool flank wear (PCD tool:r=1.6 mm, a=0; square points: 6=670 m min1, doc=1.5 mm;round points: 6=894 m min1, doc=1.5 mm).M. El-Gallab, M. Sklad/Journal of Materials Processing Technology83 (1998) 151158156Fig. 9. Effect of depth of cut on the tool flank wear (PCD tool:r=1.6 mm, a=0, 6=894 m min1; square points: doc=1.5 mm;round points: doc=2.5 mm).illustrate this point, in the case of a greater depth of cuta larger surface area of the tool flank face is exposed toabrasion.Increasing the feed rate had a beneficial effect. Asshown in Figs. 8 and 9, as the feed rate increases, thetool wear decreases. In the case of higher feed rates, fora fixed volume of metal removal, the tool surfaces willhave less contact with the abrasive PMMC. AnotherFig. 10. (a) Effect of PCD tool rake angle on tool flank wear (6=894m min1, doc=2.5 mm, r=1.6 mm; square points: 0; round points:5; star points, +5); (b) effect of PCD tool rake angle on thecutting forces (6=894 m min1, doc=2.5 mm, r=1.6 mm; squarepoints: 0; round points: 5; star points, +5); (c) SEM imageillustrating the PCD tool wear by pitting (6=670 m min1, doc=1.5mm, f=0.25 mm rev1, r=1.6 mm, a= +5).BUE (i.e. strain-hardened two-phase material underhigh temperature and pressure).At high cutting speeds (6=894 m min1(Fig. 5(b),a smaller BUE is formed, compared to the BUE formedat 6=670 m min1(Fig. 5(a); the height of the BUEwas measured perpendicular to the rake face) In con-trast, by increasing the depth of cut from 1.5 to 2.4mm, a large BUE is formed (Fig. 6(a,b), which couldbreak off the tool causing tool chipping and consequentadverse effects on the workpiece surface roughness anddimensional accuracy.Topographies of the tool indicate that the main wearmechanism of PCD is abrasion (manifested as groovesparallel to the chip flow direction). These grooves couldbe attributed to three factors. The first is that Al2O3isformed at the tool edge, which is hard enough toproduce grooving wear in the PCD. The second expla-nation for the PCD grooving is aluminium seizure andthe pull-out process of the PCD grain, as shown in Fig.7(a,b). The third possible reason behind PCD groovingis that SiC particles abrade the tools. Thus, PCD toolswith PCD grains larger than the grain size of the SiCparticles could better withstand the abrasion and mi-cro-cutting by the SiC particles. However, one shouldnote that as the size of the PCD grains increases, thefracture properties of the PCD tool deteriorates, due toan increased number of flaws in the material.The grooves that were formed on the tool face werefilled with the workpiece material. This adhering layersomewhat protected the tools rake face against furtherabrasion. Nonetheless, the tool flank face continued tobe subjected to abrasion. Hence, flank wear (Vb) wastaken as the tool life criterion with Vb1im=0.18 mm.Fig. 8 shows that as the cutting speed increases, theflank wear increases. This could be attributed to theincrease in the kinetic energy of the abrading particles,as previously hypothesized by Lane 17.Increasing the depth of cut leads to an increase in theflank wear (Fig. 9). This is attributed to enhancedabrasion by micro-cutting at the tool flank face. ToM. El-Gallab, M. Sklad/Journal of Materials Processing Technology83 (1998) 151158157Fig. 11. (a) SEM image illustrating the PCD tool wear by chipping(6=894 m min1, doc=1.5 mm, f=0.35 mm rev1, r=0.8 mm,a=0); (b) effect of tool nose radius on the tool flank wear (6=894min, doc=2.5 mm, a=0; tool FW: square points, r=1.6 mm;round pitch points, r=0.8 mm).wear in the case of negative rake angle, is the greatercutting forces encountered with such a rake angle (Fig.10(b). Moreover, the chips produced became caughtbetween the tool and the workpiece, causing damage tothe tool surface. Tools with positive rake angle showedirregular flank wear and excessive pitting in the cuttingedge zone, as shown in Fig. 10(c).The tool nose radius plays a key role in determiningthe wear mode of the tool. As the tool nose radius wasdecreased from 1.6 to 0.8 mm, the tool was found tosuffer from excessive chipping and crater wear, asshown in Fig. 11(a). This tool chipping leads to anincrease in cutting forces and flank wear, as shown inFig. 11(b). Tools with small nose radii are thus recom-mended for finishing operations where light cuttingparameters are used. Small nose radii are also expectedto yield better geometrical accuracy.5. ConclusionThe results of the machinability studies carried outon 20%SiC/Al particulate metal-matrix composites in-dicated the following.(1) The main tool wear mechanism is abrasion andmicro-cutting of tool material grains, manifested asgrooves on the tool face parallel to the chip flowdirection. All of the tools tested also suffered fromflank wear due to abrasion. There was no evidence ofchemical wear (e.g. by diffusion).(2) PCD tools sustained the least tool wear com-pared to TiN coated carbide tools and Al2O3/TiC tools.This is undoubtedly due to PCDs superior hardnessand wear resistance, as well as low coefficient of fric-tion, together with high thermal conductivity. This ledto lower cutting temperatures when PCD tools wereemployed. On the other hand, the TiN coated carbidetools and Al2O3/TiC tools suffered from excessivecrater wear and edge chipping.(3) The grooves formed on the rake face of PCDtools were filled with smeared workpiece material. Thisform of built-up edge is beneficial, since it protects thetool rake from further abrasion.(4) The cutting parameters play a key role in deter-mining the amount of tool flank wear, as well as thesize of the built-up edge. Tool wear is minimized byincreasing the feed rate, which leads to a reduction incontact between the tool and the abrading SiCp. Al-though increasing the cutting speed is expected to accel-erate the flank abrasion wear dramatically, the resultsindicated that the increase in wear is minimal. Highercutting speeds were associated with the increase in thecutting temperatures, which led to the formation of aprotective sticking thin layer of workpiece material onthe tool. This form of protective built-up edge wasprevented from growing in size by the increase speed ofadvantage gained by increasing the feed rate is thechange in chip form. At low feed rates, the chipsformed were continuous, also being difficult and haz-ardous to handle. At high feed rates and high depths ofcut ( f0.35, doc2.0 mm), the chips formed werediscontinuous. Despite the fact that in all experimentswith PCD tools high feed rates resulted in lower toolwear, a conclusive decision about the optimum cuttingparameters should take into consideration the effect ofthe cutting parameters on the surface integrity andsub-surface damage produced in the workpiece. Com-prehensive analysis of the surface integrity and chipmorphology will be presented in the Part II of thisresearch study.4.3.Effect of tool geometryThe tool rake angle had a profound effect on thewear of PCD tools. Three different rake angles wereexamined. As can be seen from Fig. 10(a), tools with 0rake angle out-performed positive and negative rakeangle tools. A possible reason for the increased flankM. El-Gallab, M. Sklad/Journal of Materials Processing Technology83 (1998) 151158158rubbing. Within the tested range of cutting parameters,the speed of 894 m min1, f=0.45 mm rev1anddepth of cut=1.5 mm resulted in the smallest toolwear. These cutting parameters enhance the productiv-ity rates upon using PCD tools.(5) PCD tools with nose radii=16 mm and rakeangle=0 also led to lower flank wear.AcknowledgementsThe authors would like to thank R. Bruski, fromDuralcan, USA and D. Dyer from GE Superabrasives,for supplying the test material and cutting tools and fortheir helpful comments throughout the research project.The experiments were conducted in the machining labo-ratories of the Intelligent Machines and ManufacturingResearch Center at McMaster University.References1 P. Rohatgi, Advances in cast MMCs,