国外刀具涂层技术的现状及发展趋势

刀具涂层技术通常可分为化学气相沉积（CVD）技术和物理气相沉积（PVD）技术两大类,分别评述如下。     

"金刚石涂层技术"成果简介

“863”新材料领域项目金刚石涂层技术包含了涂层刀具和涂层拉丝模二部分研究工作,这些研究工作同时得到了上海市科技发展基金的资助。 以氢气和丙酮(或乙醇)为原料,采用化学气相法(简称CVD法)在硬质合金(WC-Co)刀具表面或拉丝模内孔涂覆一层金刚石薄膜,就可制备得到金刚石涂层刀具或涂层拉丝模。金刚石涂层呈多晶状,厚10～30μm,它具有硬度高、导热性好、抗冲击、自润滑性能好、化学性能稳定等特点。我们研制的涂层刀具,其抗冲击性能优于PCD刀具,与硬质合金刀具相近,特别适用于非     

加工7075航空铝合金用金刚石涂层刀具的制备及其切削性能

采用热丝化学气相沉积(HFCVD)技术在WC-Co8%硬质合金刀具表面制备金刚石涂层,调节甲烷浓度等沉积工艺制备了单层金刚石涂层刀具和微米金刚石涂层(1.2 μm)、纳米金刚石涂层(200 nm)交替多层金刚石涂层刀具。以7075航空铝合金作为切削工件,在无润滑干切条件下测试了单层金刚石涂层刀具和多层金刚石涂层刀具的切削性能。实验结果表明,切削2 h后单层金刚石涂层刀具涂层脱落宽度达到35 μm,刀刃钝化;有多层金刚石涂层刀具的刃型保持完整,涂层无脱落。对单层金刚石涂层和多层金刚石涂层平面样品进行了洛氏压痕实验。结果表明,多层金刚石涂层的脱落面积约为单层金刚石涂层脱落面积的1/5到1/10,进一步说明多层金刚石涂层有更强的抵抗裂纹产生的能力。这些结果表明,金刚石多层结构能提高涂层与基体的界面结合力,延长金刚石涂层刀具的使用寿命。     

大批量微细刀具HFCVD涂层制备的温度场仿真与试验分析

采用热丝化学气相沉积法制备金刚石涂层微细刀具的过程中,刀具表面温度场分布的均匀性与稳定性对金刚石涂层的质量具有决定性的作用。本文采用有限容积法,对微细刀具表面沉积金刚石涂层过程中的温度场分布进行了仿真研究,采用Taguchi正交试验法考察了热丝直径d、热丝高度H、热丝间距D以及热丝长度L对温度场均匀性的影响,并获得了最优参数组合,即d=0.65mm,H=12mm,D=27mm以及L=160mm。对比仿真与实际测温试验结果,发现两者之间的偏差不超过4%,验证了仿真模型具有较高精度。采用仿真获得最优参数进行的沉积实验结果表明,放置在沉积区域不同位置的微细刀具表面均被涂覆了一层厚度均匀、组织结构良好的金刚石涂层,从而验证仿真结果的正确性。     

WC-Co硬质合金/CVD金刚石涂层刀具研究现状

化学气相沉积(Chemical vapor deposition,CVD)金刚石涂层刀具具有高硬度、优异的耐磨性、良好的冲击韧性和化学稳定性,能满足高效率、高精度的加工要求,逐渐成为切削铝和高硅铝合金、碳纤维增强复合材料及石墨等轻质量高强度难加工材料的主流涂层刀具。基于WC-Co硬质合金为基体的CVD金刚石涂层刀具在切削加工过程中容易发生CVD金刚石涂层的剥落,自主研发结合性能优良、长时间加工稳定的WC-Co硬质合金/CVD金刚石涂层刀具仍是该领域国内外发展的必然趋势。目前,研究者为了提高WC-Co硬质合金/CVD金刚石涂层刀具的结合性能,采用化学刻蚀法和机械处理法相结合去除WC-Co硬质合金基体表层中的Co粘结相,发现其能增强涂层与基体的结合强度,但基体表层Co粘结相含量的减少容易导致基体中形成脆化层,降低基体的强度和韧性。为了减少基体的强度和韧性损失,研究者在WC-Co硬质合金基体和金刚石涂层之间制备稳定的含Co中间化合物或沉积中间层,成功阻挡Co粘结相的热扩散。除了上述方法外,研究者还通过调控金刚石涂层工艺参数和结构,将微米晶与纳米晶金刚石层叠相结合,来提高金刚石涂层刀具的摩擦学...     

TiCN,TiAlN,TiAlCN涂层研究现状

TiAlCN等硬质涂层能提高金属工件的表面硬度、耐磨性及抗腐蚀性,从而有效提高高速旋转条件下服役的刀具、磨具及汽车零部件的精密度和使用寿命。综述了TiN添加Al、C元素形成的TiCN、TiAlN及TiAlCN涂层的结构及应用,总结了添加元素Al、C对涂层结构及性能的影响及其作用机理。归纳了近几年TiCN、TiAlN及TiAlCN涂层的制备方法,包括直流磁控溅射法(DCMS)、高功率脉冲磁控溅射法(HiPIMS)、中温化学气相沉积法(MTCVD)和激光化学气相沉积法(LCVD)等,并对多元TiN涂层的未来发展方向进行了展望。     

涂层梯度硬质合金的研究进展

主要综述了涂层梯度硬质合金的发展,对涂层梯度硬质合金基体的制备、基体涂层技术、基体表层碳含量的控制等进行了阐述.展望了梯度硬质合金的前景和发展方向.     

多弧物理气相沉积技术制备（TiAl）N超硬膜

主要介绍采用多弧物理气相沉积（ＰＶＤ）技术研制新型（ＴｉＡｌ）Ｎ超硬膜的工艺技术特点。对其膜层相结构、化学成分、显微组织等方面做了分析研究。结合工业生产实际应用进行了（ＴｉＡｌ）Ｎ与ＴｉＮ涂层刀具切削耐用度对比试验。     

刀具镀层的技术进展

综述了化学气相沉积（CVD）和物理气相沉积（PVD）工艺的特点与开发，以及CVD和PVD镀层及金刚石镀层刀具的性能和应用。中温CVD，PVD和金刚石镀层刀具等技术的进展标志着先进镀层应用时代的来临。     

"渗氮/物理气相沉积"复合涂层研究的新进展

介绍了"渗氮/物理气相沉积(PVD)"复合涂层在涂层结构设计、工艺与性能、失效与强化机制等方面研究的最新进展.与单一涂层相比,"渗氮/PVD"复合涂层表现出更好的物理力学性能,明显提高了工模具的耐用性.渗氮层的引入不仅显著地提高了基材表面的承载能力和膜/基结合力,而且还提高了钢表面的疲劳强度、耐磨性能、热冲击及化学抗力,尤其是在承受高载荷情况下的失效抗力.经过十几年的研发,复合涂层已开始进入商业应用阶段,在高速钢切削刀具和各种精密工模具上有广阔的应用前景.     

Mechanical measurement of the residual stress in thin PVD films

A practical mechanical bending plate method is proposed to calculate the residual stress present in thin physical vapour deposition films. A thin circular foil of stainless steel is coated with TiN, using an unbalanced magnetron sputtering technique. Sectioning of this foil into narrow strips leads to an easily measurable radius of curvature. With the help of calculations based on the finite element method it is shown that, if the width-to-length ratio is small, the analytical formula of Senderoff is valid. Above a certain width-to-length ratio, serious errors in calculated stress values are introduced using Senderoff. The second part of this paper describes the influences of the deposition parameters of TiN on the residual stress in the coating. An increase of the bias voltage results in a higher compressive stress, varying from −4.2 to −7.2 GPa. Experiments with different substrate materials show that the growth stress is independent of the substrate material. The total residual stress present in the coating increases with a higher magnetron current and a lower working gas pressure.

There was excellent agreement between the results of the proposed method and X-ray diffraction (Seemann-Bohlin).     

Residual stress, Young''s modulus and fracture stress of hot flame deposited diamond

Chemical vapour deposition (CVD) diamond coatings deposited on various substrates usually contain residual stresses. Since the residual stress affects the adhesion of the coating to the substrate, as well as the performance of the coating/substrate composite in many technical applications it is of importance to study the magnitude of these stresses.

In the present study the hot flame method was used to deposit diamond coatings on cemented carbide inserts by scanning the surface with a nine flame nozzle. By varying the oxygen to acetylene flow ratio and the deposition time coatings of different qualities and thicknesses were obtained. The residual strain/stress of the coatings was measured by three different methods: X-ray diffraction using the sin² (Ψ) method, Raman spectroscopy and disc deflection measurements. To extract the residual stress from the strain data the Young's modulus was obtained from bending tests of diamond cantilever beams manufactured from free standing diamond films. The latter technique was also used to determine the fracture stress of the diamond films.

All deposited coatings displayed a residual compressive strain/stress state. The residual strain in the diamond coatings did not vary with coating thickness (1.5 μm to 20 μm) but was found to increase from −1.8 × 10⁻³ to −2.2 × 10⁻³ with decreasing diamond quality. The compressive residual stress was found to decrease from −2 GPa to −1.3 GPa with decreasing diamond quality. This is mainly due to a decrease in Young's modulus (from 1.1 TPa to 0.6 TPa) with decreasing diamond quality. Also the fracture stress was found to decrease (from 1.8 GPa to 0.8 GPa) with decreasing diamond quality. The three methods used for measuring the stress state in the coatings, X-ray diffraction, Raman spectroscopy and deflection measurement, all give the same result. The deflection technique has the advantage that no information about the elastic properties of the coating is needed, whereas Raman spectroscopy has the best lateral resolution (≈5 μm) and is the fastest method (≈5 min).     

Study of the delamination of diamond coatings under thermal stress

The influence of the thickness of CVD diamond coatings on the adhesion to a substrate, after cooling down from deposition temperature to room temperature, has been studied experimentally and theoretically. Diamond layers have been deposited at 850°C on W substrates by microwave plasma enhanced CVD. Cooling down of the substrate-diamond coating system to room temperature induces thermal stresses, due to different thermal expansion coefficients of coating and substrate. For thick diamond coatings a total and sudden delamination could be observed as a consequence of these stresses. On the contrary thin coatings, produced under identical circumstances, adhered well. These phenomena have been modelled and explained by the use of an energetic criterion for the delamination of a two-layer system under thermal stress. From the model a critical thickness of the coating can be calculated. Above this critical thickness, delamination will suddenly occur. The calculations also predict that for intermediate coating thicknesses delamination can easily be induced by external causes.     

Evaluation of PVD nitride coatings, using impact, scratch and Rockwell-C adhesion tests

In this work the scratch test, the impact test and the Rockwell-C adhesion test were compared by investigating the adhesion properties of three types of sputtered physical vapour deposition coatings: TiN, CrN and Cr₂N. Each coating type was deposited on polished SAE 52100 steel, with different thicknesses in the nominal range of 2–20 μm, to evaluate the thickness influence on the test results. All the tests showed a ductile behaviour for the TiN coating with small delaminations and a brittle behaviour for the CrN and Cr₂N coatings with relatively large delaminations. An increase of the dimensions of the delaminations with increased coating thickness was detected for all layer types.

With the scratch test a significant increase in upper critical load with layer thickness was observed for all of the coatings. However, there was considerable variability especially for the Cr₂N coatings. The impact tests showed no coating failure for the TiN layer, and a decreasing impact crater volume with increasing layer thickness, whereas the CrN and Cr₂N layers failed after 10³ impacts and showed an increasing impact crater volume with increasing layer thickness.

The studies demonstrate the usefulness of using these test methods for differentiating between the behaviour of different coatings under various contact conditions.     

Creep studies of the EB PVD coatings with a ceramic layer

The effect of the electron beam physical vapor deposition CoCrAlY and CoCrAlY/ZrO₂ + 8wt.%Y₂O₃ coatings with different thickness of the ceramic layer on the life of the nickel base alloys were investigated. Coatings with a ceramic layer improved the time to failure of the base alloy. The dependence of the stress-rupture properties of alloys with three layers of metal/ceramic coating on the thickness of the zirconia layer is expressed by the curve with the maximum corresponding to a 100 μm thickness.     

Nanometric-layered CrN/TiN thin films: mechanical strength and thermal stability

Nanometric-layered CrN/TiN coatings were deposited using unbalanced magnetron sputtering. The layered coating structure was characterised by X-ray diffractometry, and the mechanical properties were measured by nano-indentation and scratch test. High temperature annealing at 400-750 °C was carried out to investigate the thermal stability of the coating structure and mechanical properties. For comparison, samples of TiN and CrN deposited under similar conditions were also annealed and tested. The results showed that nano-layered CrN/TiN has excellent mechanical and thermal properties. Nano-hardness of 40 GPa and scratch adhesion of 80 N were achieved at a wavelength of 7.5 nm and a substrate bias of −80 V. The coating demonstrates application prospects in the stamping/cutting tools industry.     

Recent Advances of Laser Coating Technology in China

Recent advances in laser coating technologyincluding laser cladding,laser surface alloying andlaser vapour deposition in China are reviewed inthis paper.     

NbSi基原位复合材料表面包埋渗制备SiCrY共渗涂层

通过热力学计算分析了分别使用NH₄Cl和CrCl₃·6H₂O两种不同激活剂时, 各个共渗元素的卤化物蒸汽压分压的变化, 得到了实现Nb-Si基原位复合材料上Si-Cr-Y三元包埋共渗的最佳条件。采用包埋共渗法在Nb-Si基原位复合材料表面制备了Si-Cr-Y共渗涂层, 研究了涂层的组织形貌、 成分及其相组成。结果表明: 使用NH₄Cl做激活剂, 通过调整包埋渗料的成分, 可以在适当的温度下实现Si-Cr-Y的三元共渗。当渗料成分为12Cr-6Si-0.75Y₂O₃-5NH₄Cl-76.25Al₂O₃(质量分数)时, 在1350℃可以实现Si-Cr-Y三元共渗。制备的涂层具有多层结构, 分为外层、 内层和明显的互扩散层。互扩散层的存在, 表明涂层的形成是一个连续生长过程, 伴随着Cr、 Si、 Y元素向基体内的扩散。涂层的主要成分由Cr₂(Nb,Ti)、 (Nb,Ti)₅Si₃和HfSi₂组成, Y元素的添加起到了细化涂层的作用。     

CrAlTiN镀层在精密铣刀上的应用研究

介绍了通过闭合场非平衡磁控溅射离子镀技术制备出的CrAlTiN超硬纳米梯度复合镀层在铣刀上的应用,试验结果表明,铣刀在离子镀处理之后寿命提高为原来的3倍.采用SEM和TEM分析了镀层铣刀磨损后的表面形貌及无镀层铣刀的失效方式,揭示了镀层提高铣刀寿命的原因.     

Deposition of diamond-like carbon on a titanium biomedical alloy

Much of the orthopedic community now believe that the long-term failure of total hip and knee prostheses is directly or indirectly due to the production of wear particles, particularly polyethylene wear particles which are produced at the articulating interface between the metal component and the high molecular weight plastic component. Therefore, a friction and wear reducing coating on the metal component, which is also biocompatible, should reduce the production of the polyethylene wear particles and dramatically extend hip-implant life. Diamond-like carbon (DLC), with its extreme smoothness, hardness, low coefficient of friction, and biocompatibility is an excellent candidate for such an application. One of the key issues that may limit the utility of DLC in this application is the adhesion of this material to common biomedical alloys. We will show that high adhesion strength between sputter-deposited DLC and a silicon-coated titanium biomedical alloy can be easily achieved.