微米、纳米及微/纳米复合金刚石涂层的切削性能研究

利用化学气相沉积(chemical vapor deposition,CVD)法在硬质合金上制备纳米、微米以及微/纳米复合金刚石涂层,并进行了切削对比试验。通过测试已加工材料的表面粗糙度和金刚石涂层刀具前、后刀面磨损,对比分析了不同金刚石涂层的切削性能,同时总结了CVD金刚石涂层刀具的失效形式及机理。结果表明:纳米金刚石涂层刀具切削加工后的表面粗糙度值最小,Ra=0.942μm;微米金刚石涂层刀具切削加工表面粗糙度值最大,Ra=1.631μm;纳米涂层刀具的后刀面磨损最大,约为微米涂层的2倍,复合涂层的5倍;微/纳米复合金刚石涂层刀具膜/基结合力高,前、后刀面的金刚石涂层没有出现脱落,且刀具的磨损量较少;金刚石涂层刀具的主要失效形式是涂层的过早脱落,其失效主要是由金刚石涂层的残余应力大、涂层化学纯度低、内部产生微裂纹多,以及切削时表面粗糙度高、切削力大和刀具积屑瘤普遍等原因引起的。     

CVD金刚石涂层刀具高速铣削加工石墨模具研究进展

介绍了模具石墨的性能特点和切削加工机理,指出了复杂结构电火花石墨模具铣削加工中的困难,提出了CVD金刚石涂层刀具的解决方案。在此基础上介绍了国内外CVD金刚石涂层刀具在石墨模具高速铣削加工的工艺特点以及加工中CVD金刚石涂层刀具的磨损机制和破损失效形式,并列举了CVD金刚石涂层刀具在石墨模具高速铣削加工的应用,指出CVD金刚石涂层刀具高速铣削加工可解决石墨模具难以加工这一难题,若能进一步解决CVD金刚石涂层刀具的膜-基结合力和表面粗糙度问题,预期CVD金刚石涂层刀具高速铣削加工石墨模具可得以广泛推广应用。     

CVD金刚石涂层刀具在石材铣削中的磨损特性研究

为了揭示CVD金刚石薄膜涂层刀具在硬脆材料切削中的刀具切削性能与磨损机理,利用不同沉积参数下的金刚石涂层刀具对天然石材进行了高效铣削实验。针对金刚石涂层刀具和未涂层硬质合金刀具的磨损周期和切削性能,分析刀具切削力和工件表面粗糙度随后刀面磨损面积的变化规律,总结刀具磨损机理。实验结果表明:金刚石涂层刀具切削寿命高于未涂层硬质合金刀具;金刚石刀具的磨损周期可以分为初始磨损区、稳定磨损区和加剧磨损区3个阶段,其中甲烷浓度为1%的金刚石涂层刀具寿命较长,切削性能稳定;金刚石涂层刀具的磨损机理主要包括裂纹作用下的涂层剥落、涂层内部晶间断裂和粘结磨损,其中裂纹作用下的膜-基涂层剥落磨损为刀具失效的主要磨损机制。     

化学气相沉积金刚石薄膜刀具膜/基附着性能研究现状

CVD金刚石薄膜涂层刀具被认为是能最早实现CVD金刚石工业化应用的领域之一.目前,限制CVD金刚石薄膜涂层刀具产品大规模产业化应用的主要原因,是金刚石薄膜与硬质合金基底之间粘附性能较差.如何提高膜/基粘附性能,确保CVD金刚石薄膜涂层刀具优异性能的发挥、涂层刀具的使用寿命和加工性能,已成为材料科学工作者迫切需要解决的问题.介绍了影响CVD金刚石薄膜硬质合金刀具膜/基附着性能的主要因素、改善金刚石薄膜与硬质合金基体之间附着力的途径以及表征膜/基附着力的测试方法等方面的研究成果,并对提高低压气相金刚石薄膜硬质合金刀具膜/基附着性能的研究现状进行了分析.     

喷砂添加微裂纹对CVD涂层硬质合金综合性能的影响

本文采用干喷砂法对CVD涂层硬质合金进行表面处理,在涂层中添加了不同裂纹间距的微裂纹.通过4种不同裂纹间距的横向断裂强度(TRS)样品和涂层硬质合金刀片样品,借助断裂强度试验机、X射线应力检测仪、扫描电镜、压痕试验机和切削试验,研究了微裂纹间距对涂层硬质合金横向断裂强度、残余应力、涂层结合强度、刀片抗崩裂性和耐磨性的影...     

CVD金刚石涂层硬质合金刀具研究进展

CVD金刚石涂层硬质合金刀具结合了金刚石和硬质合金的优异性能,是切削加工的理想材料,具有广阔的发展前景。当前限制CVD金刚石涂层刀具应用的主要问题是金刚石涂层与刀具基体之间的附着性能较差,其主要原因是粘接相Co对CVD沉积存在不利影响以及涂层与基体之间热膨胀系数存在较大差异。本文综述了提高界面结合强度和降低涂层表面粗糙度的方法,重点介绍了在界面添加过渡层来提高界面结合强度,并指出在硬质合金基体和CVD涂层之间添加过渡层和开发纳米CVD涂层是CVD金刚石涂层刀具今后的发展方向。     

硬质合金CVD金刚石涂层最新进展

金刚石因具有优异的物理化学性能被认为是理想的刀具材料。硬质合金基底上涂覆CVD金刚石薄膜有利于改善刀具的加工性能和寿命,但涂层和基底之间存在热膨胀系数差异以及合金中Co对沉积有不利影响,使得薄膜附着力较差。本文综述了近几年来各种提高CVD金刚石涂层刀具切屑性能的方法,从提高薄膜附着力和改善金刚石膜的质量两个方面进行了讨论。并介绍了国外较先进的CVD金刚石涂层刀具的应用,随着技术的不断成熟,CVD金刚石涂层将会有更为广泛的应用。     

CVD金刚石涂层硬质合金刀具的研究进展

概述了CVD金刚石涂层硬质合金刀具的研究现状及存在的问题,重点对近五年CVD金刚石涂层硬质合金刀具基体预处理方法、涂层内应力的表征方法等方面的研究现状进行了综述。     

CVD金刚石刀具微铣削AA356铝合金的磨损分析

AA356铝合金已广泛应用于航空航天等领域,但其在微细加工过程中刀具磨损严重且相关机理尚不明晰.为揭示工艺参数对CVD金刚石刀具微铣削AA356铝合金的刀具磨损影响机制,基于正交试验和响应曲面法开展了微细加工试验,采用最小二乘法和粒子群优化算法建立刀具磨损的预测方程,分析刀具的磨损形貌和切削用量对刀具磨损的影响规律.结...     

CVD金刚石涂层刀具切削性能与磨损机理研究

针对普通刀具切削质量差、刀具耐用度低等问题,对CVD涂层刀具制备方法及切削性能进行研究。首先以硬质合金刀具为基体通过CVD方法制备金刚石涂层,分析涂层表面形貌。然后在不同条件下进行铝合金材料的干式切削试验,分析金刚石涂层对切削力、切削温度以及工件表面粗糙度的影响规律。最后,通过对刀具磨损机理的分析,讨论涂层对刀具使用寿命的影响。研究结果表明,所制备的涂层刀具能够降低切削力和切削温度,大大提高刀具的切削性能和工件的表面质量,并能有效提高刀具使用寿命。     

Finite element analysis of stress distribution in thermal barrier coatings

A numerical simulation of crack development within APS TBC systems is presented. The TGO thickening and creep deformation of all system constituents is modelled. Two dimensional periodic unit cell is used to examine the effect of interfacial asperity on stress distribution and subsequent delamination of APS TBC. A study of cyclic loading and of creep of the base material on the stress distribution close to the asperity at the TGO/BC interface is made, revealing a small in?uence influence of both on the stress state in the thermal barrier coating system subjected to temperature loading. Cohesive zone elements at the oxide/ceramic interface model the development of the interfacial micro-crack. The finite element analysis shows that the development of the interfacial crack allows for a micro-crack formation within APS TBC. Subsequent TGO growth results in a tensional zone within the oxide layer. Linking of the micro-cracks at the interface and within TBC through TGO could lead to a coating delamination in the unit cell.     

压痕法研究镶嵌结构界面金刚石膜粘附性能

在铜基体上沉积Cu(Cr)-diamond复合过渡层,用热丝CVD法在复合过渡层上沉积出金刚石膜。用压痕法对沉积的金刚石膜/基结合性能进行了研究。结果表明,在Cu-diamond上沉积的金刚石膜,用147 N压痕时压痕边缘出现大面积崩落,并在基体表面留下被拔出的金刚石凹坑;在Cu-diamond中掺入微量Cr,压痕边缘只形成环形裂纹,增大压痕载荷至441 N,环形裂纹区域增大,并出现部分崩落,崩落区域有被切断的金刚石残留。在Cu-diamond复合层中掺入微量Cr能显著提高金刚石膜/基结合力。     

厚度与分层耦合效应对X60管线钢断裂韧性的影响

通过对厚度分别为3,6,9,12和15mm的CT试样的断裂韧性实验和微观断口分析,研究了X60高韧性管线钢的断裂韧性和裂纹扩展阻力曲线的厚度与分层裂纹耦合效应,结果表明,分层裂纹与厚度方向的离面应力存在约束互相作用,厚度增加,分层开裂加剧,局部有效厚度并未增加,导致断裂过程中裂纹端部的一三维应力约束总是近平面应力的低约束状态,表观断裂韧性不随厚度变化,在有分层裂纹出现时,无法靠增加试样厚度获得材料的平面应变断裂韧性,由于分层与厚度的耦合作用与裂纹扩展方向与厚度方向的相对方位密切相关,应用穿透裂纹的表观断裂韧性数据进行管道结构的安全评定并不完全可靠,研究还表明,塑 性区修正的有效应力强度因子与弹塑性J积分参量在失稳扩展前保持良好的等效性。     

CVD金刚石涂层中热应力的有限元模拟

在CVD涂层系统中,由于各种材料物理性能的差异,涂层在从沉积温度冷却到室温的过程中会产生热应力,影响膜基之间的附着力.为了考察各种因素对产生热应力的影响,利用热固耦合有限元方法分析了不同沉积条件下硬质合金基体上金刚石膜的热应力情况,还讨论了有不同过渡层的情况.对各情况下的轴向、径向和剪切应力做了比较分析.结果发现沉积温度和金刚石膜厚度对热应力影响较大,而过渡层厚度和物理性能对热应力影响不大.     

Analysis of tool wear and residual stress of CVD diamond coated cemented carbide tools in the machining of aluminium silicon alloys

Aluminium alloys have found increasing applications in the automotive and aeronautical industries in recent years. Due to their extraordinary properties however, the machining of these alloys still poses difficulties, and requires the optimized combination of cutting tool material and geometry. The potential of CVD diamond coated carbide tools has been demonstrated in recent years, however tool wear and short tool life remain as issues to be resolved. Key to increasing the tool life of CVD diamond coated tools is the further development of the coating process to optimize the coating adhesion. An understanding of the substrate and coating residual stress profiles must be gained in order to achieve this. Compressive residual stresses in cutting tools can lead to a higher crack resistance, but also to early coating delamination and tool failure. To analyze the influence of residual stresses on the coating quality and tool life, the residual stress profiles of tungsten carbide substrates and CVD diamond coatings were measured using X-ray and synchrotron radiation. The influence of the tungsten carbide substrate type and the CVD diamond coating process on the residual stress profiles was thus determined. In order to analyze the performance of the coated tools and the influence of the residual stresses on the tool lifetime, machining tests were performed with two aluminium silicon alloys. The tool wear, tool lifetime and workpiece quality were examined. Finally, many of the commonly used wear tests used to analyze the wear resistance of tool coatings cannot be implemented for CVD diamond coatings due to their high hardness. An impact test was therefore constructed to allow the determination of the wear resistance of CVD diamond tools.     

基于内聚力单元与XFEM的热障涂层失效分析

为了更好的理解热障涂层的失效机理,文中运用ABAQUS有限元软件来分析热障涂层的失效情况,使用内聚力单元和扩展有限元（XFEM）两种方法研究热障涂层TGO界面开裂与陶瓷涂层（TC）和氧化层（TGO）内随机裂纹的萌生与扩展,研究竖直裂纹与水平裂纹的关系.结果表明,热障涂层TGO界面的开裂首先出现在TGO/TBC波谷处.陶瓷涂层和氧化层内随机裂纹的萌生同样发生在TGO/TBC波谷处.竖直裂纹的存在可以抑制水平裂纹的萌生与扩展,且其在TGO/TBC波谷处的扩展长度比在TGO/TBC波峰处的扩展长度更长,说明TGO/TBC波谷区域是个危险区域,在此区域容易引发裂纹的萌生与扩展.     

Identification of delamination failure of boride layer on common Cr-based steels

Adhesion is an important aspect in the reliability of coated components. With low-adhesion of interfaces, different crack paths may develop depending on the local stress field at the interface and the fracture toughness of the coating, substrate, and interface. In the current study, an attempt has been made to identify the delamination failure of coated Cr-based steels by boronizing. For this reason, two commonly used steels (AISI H13, AISI 304) are considered. The steels contain 5.3 and 18.3 wt.% Cr, respectively. Boriding treatment is carried out in a slurry salt bath consisting of borax, boric acid, and ferrosilicon at a temperature range of 800–950 °C for 3, 5, and 7 h. The general properties of the boron coating are obtained by mechanical and metallographic characterization tests. For identification of coating layer failure, some fracture toughness tests and the Daimler-Benz Rockwell-C adhesion test are used.     

微弧表面处理对AZ31B镁合金耐腐蚀及耐腐蚀疲劳性能的影响

采用微弧表面处理技术(微弧氧化MAO和微弧复合MCC)在AZ31B镁合金基体上制备出不同断面结构的防护涂层。通过电化学腐蚀及腐蚀疲劳测试方法,研究了MAO、MCC涂层的电化学腐蚀及腐蚀疲劳性能。结果表明,生长10 min的MAO涂层具有较好的耐电化学腐蚀性能。MAO涂层表面存在微孔和微裂纹,在应力条件下微孔和微裂纹作为疲劳断裂的裂纹萌生点,可加速裂纹的萌生与扩展,使其腐蚀疲劳寿命相较AZ31B合金基体降低了55%。而具有MCC涂层的AZ31B合金试样腐蚀疲劳极限为(64.0±5.4) MPa,比AZ31B合金基体提高了59%。在低应力载荷下(＜80 MPa),微弧复合涂层试样的腐蚀疲劳强度得到明显提高。     

再制造件涂覆层内部裂纹扩展行为研究

目的研究再制造件涂层内部不同形状、尺寸的裂纹扩展行为。方法利用扩展有限元和内聚力单元结合的方法,通过设定断裂能G值作为控制裂纹扩展的参数,对三点弯曲试验以及拉伸试验下涂覆层内部的裂纹进行模拟,并通过实验进行验证。结果随着载荷的增加,涂层中的垂直裂纹和45°倾斜裂纹均沿着涂层厚度方向扩展,到达界面时裂纹发生偏转,沿着界面继续扩展而并没有越过涂层-基体界面向基体扩展。模拟得到三点弯曲试验下初始长度为0.2 mm的垂直裂纹和45°倾斜裂纹开裂的临界载荷分别为3.47 k N和4.49 k N,裂纹长度增加至0.3 mm时,临界载荷降低为3.29 k N和4.31 k N。裂纹越靠近试件中心,临界载荷越小,越易发生裂纹扩展现象。另一方面,在拉伸试验下,0.2 mm的垂直裂纹的临界开裂载荷(3.47 k N)小于投影长度相同的倾斜裂纹的临界载荷(5.21 k N),而与拉应力平行的裂纹并未扩展。实验得到0.2 mm的垂直裂纹在弯曲试验下的平均临界载荷为3.49 k N,而倾斜裂纹为4.46 k N。结论三点弯曲试验下,垂直裂纹比倾斜裂纹更危险,初始长度越长、越靠近试件中心的裂纹越易发生裂纹扩展现象。在拉伸试验下,与拉应力平行的裂纹并未扩展,最安全。模拟结果与实验相近,验证了模拟的正确性。