金属陶瓷及硬质合金表面CVD/PVD涂层的摩擦与切削性能

为研究涂层沉积方式对金属陶瓷和硬质合金性能的影响,采用粉末冶金技术制备了Ti(C,N)基金属陶瓷和YT15硬质合金,在基体表面先后采用CVD和PVD制备涂层。采用SEM、EDS等手段对涂层的微观组织和元素含量进行分析,并对涂层试样进行划痕、摩擦因数、切削性能检测。结果表明,通过复合CVD+PVD工艺,CVD涂层和PVD涂层结合良好。不论是金属陶瓷还是硬质合金,CVD涂层的膜基结合力和摩擦因数均为最大,PVD涂层最小,复合CVD+PVD涂层介于两者之间。对于金属陶瓷和硬质合金而言,复合CVD+PVD涂层的切削性能最好,CVD涂层最差,PVD涂层介于两者之间。切削过程中的磨损机理主要是氧化磨损和磨粒磨损。     

Elevated temperature repetitive micro-scratch testing of AlCrN,TiAlN and AlTiN PVD coatings

In developing advanced wear-resistant coatings for tribologically extreme highly loaded applications such as high speed metal cutting a critical requirement is to investigate their behaviour at elevated temperature since the cutting process generates frictional heat which can raise the temperature in the cutting zone to 700–900 °C or more. High temperature micro-tribological tests provide severe tests for coatings that can simulate high contact pressure sliding/abrasive contacts at elevated temperature. In this study ramped load micro-scratch tests and repetitive micro-scratch tests were performed at 25 and 500 °C on commercial monolayer coatings (AlCrN, TiAlN and AlTiN) deposited on cemented carbide cutting tool inserts. AlCrN exhibited the highest critical load for film failure in front of the moving scratch probe at both temperatures but it was prone to an unloading failure behind the moving probe. Scanning electron microscopy showed significant chipping outside the scratch track which was more extensive for AlCrN at both room and elevated temperature. Chipping was more localised on TiAlN although this coating showed the lowest critical loads at both test temperatures. EDX analysis of scratch tracks after coating failure showed tribo-oxidation of the cemented carbide substrate. AlTiN showed improved scratch resistance at higher temperature. The von Mises, tensile and shear stresses acting on the coating and substrate sides of the interface were evaluated analytically to determine the main stresses acting on the interface. At 1 N there are high stresses near the coating-substrate interface. Repetitive scratch tests at this load can be considered as a sub-critical load micro-scale wear test which is more sensitive to adhesion differences than the ramped load scratch test. The analytical modelling showed that a dramatic improvement in the performance of AlTiN in the 1 N test at 500 °C could be explained by the stress distribution in contact resulting in a change in yield location due to the high temperature mechanical properties. The increase in critical load with temperature on AlTiN and AlCrN is primarily a result of the changing stress distribution in the highly loaded sliding contact rather than an improvement in adhesion strength.     

Characterization of mechanical properties of suspension plasma sprayed TiO2 coatings using scratch test

The study aimed at characterizing mechanical properties of TiO₂ coatings obtained by the use of aqueous suspensions of fine rutile and anatase particles onto metal substrates. Thickness of the coatings was found with the use of optical microscope observations of metallographical cross-sections. The coatings morphology was found with scanning electron microscope (SEM) and their phase composition was determined by X-ray diffraction method. The mechanical properties were characterized using scratch test. The test enabled to characterize the adhesion of coatings by determination of critical force necessary to peel off the coatings from the substrate and, on the other hand, to estimate their cohesion by the measurement of the scratch hardness. The hardness was calculated using the width of the scratch and the value of force applied. The design of experiments (DOE) of spraying with the use of a 2³ full factorial plan was applied to rutile powder. The coatings were sprayed onto aluminium substrate. The DOE enabled to find the effects of three principal parameters, i.e. electric power input to plasma, spray distance and suspension feed rate onto coating adhesion expressed by critical force. A preliminary data for anatase powder sprayed with one set of operational parameters onto stainless steel substrate are also shown.     

Adhesion and dynamic impact wear of nanocomposite TiC-based coatings prepared by DCMS and HiPIMS

Nanocomposite nc-TiC/a-C:H coatings exhibit a unique combination of mechanical properties such as high hardness, and low friction and wear. These physical and mechanical properties make those coatings attractive for application in industry. However, the properties of the whole coating/substrate system such as adhesion of the coating to substrate and its response on repeated impact loading known such as dynamic impact wear are also important for industrial applications. Thus, this paper is focused on the adhesion and the dynamic impact wear of nc-TiC/a-C:H coatings prepared by the hybrid PVD-PECVD process. Two series of nc-TiC/a-C:H coatings with a different amount of carbon were deposited onto commonly used industrial cemented tungsten carbide substrates using DC magnetron sputtering (DCMS) and the high power impulse magnetron sputtering (HiPIMS) of a titanium target in argon and acetylene mixture atmosphere. Both series of coatings were analysed using a scratch test and dynamic impact tester with an impact load of 600 N. The HiPIMS prepared coatings exhibited lower thickness and lower thicknesses of the Ti adhesive interlayers between the substrates and coatings than the DCMS prepared coatings. Thus, the adhesion and the impact wear of both series were discussed separately. These properties were discussed with respect to the coating microstructure, phase composition and mechanical properties such as the hardness H, the effective elastic modulus E, and the H/E and H³/E² ratios. The scratch adhesion of coatings depended on the H³/E² ratio and coating microstructure, hardness and surface roughness. The impact wear of the nc-TiC/a-C:H coatings depended on the H/E ratio and coating microstructure.     

The influence of composition and processing parameters on the mechanical properties and erosion response of Ni + TiB2 coatings

Sputtered Ni + TiB₂ coatings have been shown to protect Inconel* 718 and Ti-6A1-4V substrates from solid particle erosion. However, before new erosion-resistant coatings can be efficiently designed, it is essential that the role of mechanical properties in determining erosion resistance be fully understood. In this investigation, nanoindentation techniques were used to quantify the effects of substrate preparation, coating composition, and sputtering process parameters on the elastic moduli and indentation hardness of thin coatings deposited on Ti-6A1-4V and Inconel 718 substrates. The influence of these parameters on coating adhesion was determined using a conventional scratch test. Elastic moduli, indentation hardnesses, and coating adhesion were correlated with erosion behavior. The erosion resistance of those coatings that exhibited microscopic ductility is dependent on the nodule diameter and coating properties such as hardness, elastic modulus, and fracture toughness. Inconel 718 is a trademark of The International Nickel Co.     

深振荡磁控溅射复合沉积CrN/TiN超晶格涂层的摩擦学性能

研究了IN718高温合金、WC-6%Co硬质合金和Si(100)基体上深振荡磁控溅射复合沉积CrN/TiN超晶格涂层的摩擦学性能。研究表明,涂层的生长对基体的类型没有选择性。随着基体硬度的升高,划痕结合力失效临界载荷增大,涂层结合力失效机制由翘曲失效转变为基体/涂层协同变形,未发现涂层的剥落失效。载荷为2N时,磨损机制由磨粒磨损和氧化磨损转变为轻微磨粒磨损。载荷为4 N时,IN 718基体上涂层的磨损机制为严重的氧化磨损,WC-6%Co基体上的涂层的磨损机制为磨粒磨损和氧化磨损,氧化物的产生、堆积和转移导致摩擦系数的波动。     

Evaluation of adhesion and fatigue of MoS2-Nb solid-lubricant films deposited by pulsed-dc magnetron sputtering

The thin film deposition for tribological applications becomes more and more widespread. The tribological performance of the overlay coatings correlates with coating-substrate adhesion. Hence, it is important to measure adhesive strength. The scratch adhesion test for thin films is extensively used. In this work, MoS₂-Nb coatings deposited by closed-field unbalanced magnetron sputtering (CFUBMS) have been scratch tested in two modes. A multi-mode operation was used as sliding-fatigue, like multi-pass scratching in the same track at different fractions of critical load (unidirectional sliding) and a standard mode using progressive load operation. Failure mechanisms are discussed according to examination of response of very dense microstructure and the adhesion value. The critical load to the first failure (L_C1) was 15 N but the final adhesion value from the film and substrate interface was 120 N (L_C2) as function of the coating thinning. The coefficient of friction (COF) from the multi-scratch for MoS₂-Nb started at a very high value of around 0.067, 0.073, and 0.093 under 5, 8, and 15 N loads respectively and then drops to 0.006, 0.035, and 0.065 at the end of the 1000 cycles. The most significant finding in the test is that when the multi-scratch passes reached to 1000 cycles, micro scale fatigue failures disappeared.     

硬质合金PECVD设备的研究

等离子体增强化学气相沉积 (PECVD)是一种利用高压电场 ,使含有涂层元素的化合物或单质气体激发成等离子体 ,加速化学反应 ,降低沉积温度、提高沉积速率的一种涂层技术 ,使硬质合金表面性能强化 ,并保持基体原有抗弯强度。本文主要介绍了一种硬质合金PECVD设备 ,该设备结构简单 ,能实现低温条件下的化学气相沉积 ,等离子体起到增强沉积反应的作用 ,实验表明该设备能较好地完成TiN -TiCN复合涂层 ,也为进一步研究提供了参考。     

The Properties and Applications of MoS_2/Ti Composite Coatings in Dry Cutting and Forming

MOLYBDENUM DISULFIDE COATIGS have beensuccessfully used in vacuum and aerospaceenvironments in the past30years.In recent years,theapplication of MoS2coatings in ambient or high humidenvironments has been drawing increasing attentions.The main obstacle to the use of MoS coating inambient conditions is its sensitivity to humidity.Fig.1shows the cases that may degrade the humidityresistance of MoSx coatings,such as the columnarstructure,low density,edge orientation of the coatings;and…     

微喷砂预处理对硬质合金上沉积类金刚石薄膜结合力的影响

针对镀前不能使用高能离子轰击清洗的硬质合金工件,采用正交法设计微喷砂工艺,用320目白刚玉对YG6硬质合金样品进行微喷砂预处理后,利用阳极层流型气体离子源和非平衡磁控溅射复合技术制备梯度过渡类金刚石薄膜.结果表明:类金刚石薄膜厚度为2.7 μm,平均显微硬度高达2 677 HV_(0.025,15),平均摩擦因数低至0.105;未预处理的硬质合金样品的膜/基结合力为30 N,而微喷砂预处理后的样品,其膜/基结合力显著提高,最高可达55.7 N;微喷砂各个因素对膜/基结合力的影响程度不同,其中喷砂压力是主要影响因素,喷砂距离和喷砂时间影响较小;优化后的微喷砂预处理工艺参数是:喷砂压力:0.10 MPa;喷砂距离:75 mm;喷砂时间:120 s.     

Improvement of a-C:H film adhesion by intermediate layers and sputter cleaning procedures on stainless steel, alumina and cemented carbide

The adhesion of amorphous hydrogenated carbon (a-C:H) films deposited in a radio frequency (r.f.) plasma discharge on stainless steel, alumina and cemented carbide with different intermediate layers (Ni, Ti and TiC) and sputter cleaning procedures was studied. The composition of the carbon films and the intermediate layers as well as the interface between the coating and the substrate was determined by secondary ion mass spectroscopy (SIMS). The adhesion experiments were carried out using a scratch tester. Tested specimens were also studied by scanning electron microscopy (SEM) to reveal the morphology of the coatings and the scratches.

Without any intermediate layer, the a-C:H coatings generally had insufficient adhesion to the substrate materials studied. For stainless steel and cemented carbide substrates, the TiC intermediate layer and, for alumina substrates, the titanium intermediate layer gave the best adhesion values evaluated by the scratch test. Also, the sputter cleaning of the substrates prior to deposition was necessary for sufficient adhesion of the coating. The intermediate layers also change the failure mode of the coating in the scratch test in some cases.     

Influence of nitrogen implantation into HSS substrate on internal stress and adhesion strength of c-BN films

Cubic boron nitride(c-BN) films were deposited on HSS substrate implanted with nitrogen ion by RF-magnetron sputtering. The films were analyzed by bending beam method, scratch test, XRD and AFM. The results show that the implantation of N ion can reduce the internal stress and improve the adhesion strength of the films.The critical load comes to 16.92N, compared to 1.75N of c-BN film on the unimplanted HSS. AFM shows that the surface of the c-BN film on the implanted HSS is low in roughness and small in grain size. The phase structure of the nitrogen implanted layer was analyzed by XRD. The influence of nitrogen implanted layer on the internal stress and adhesion strength of c-BN films were also investigated.     

Adhesion evaluation of PVD coatings to aluminium substrate

In this study the adhesion of physical vapour deposition coatings to aluminium substrate has been evaluated using a modified test similar to the scratch hardness method. The technique relies on the development of a number of scratches of different width on the coated surface produced at a range of loads. Metallic titanium and titanium nitride coatings of different thicknesses were deposited by a PVD technique. The effect of coating structure, process parameters, and the presence of an interlayer between the coating and the substrate was investigated. Experimental data show that the technique can be used to evaluate the adhesion of PVD coatings to aluminium substrates. The sensitivity of the test method is sufficiently high to characterise between coatings produced under different conditions, but the interpretation of the results is not always straightforward. Comparison of the results indicate that the method could provide useful information on coating performance, although it suffers from many problems associated with the critical load in the conventional scratch adhesion test.     

Influence of laser substrate pretreatment on anti-adhesive wear properties of WC/Co-based TiAlN coatings against AISI 316 stainless steel

To improve the anti-adhesive wear properties of WC/Co-based TiAlN coatings, a laser substrate surface pretreatment was examined. The cemented carbide substrates were textured with a Nd:YAG laser, in three different scanning speeds, and then coated with a PVD TiAlN film. The anti-adhesive wear properties of each surface were evaluated via the ball-on-disk wear test and turning experiments. Additionally, characterization tests such as variable depth scratch test were also performed in order to verify the coating adhesiveness and to explain the results of the wear and machining tests. The results reveal that the anti-adhesive wear properties of the three TiAlN coated textured samples are significantly improved over that of the conventional one; the adhesion of TiAlN coatings is greatly improved by using Nd:YAG laser substrate pretreatment. Moreover, laser-scanning speed has a profound effect on the adhesion strength of the pretreated samples. In the experiments, the lowest scanning speed (5 mm/s) is most effective in providing a greater mechanical locking of the coatings upon the substrate and a more matching chemical property between substrate and coating materials, thus increasing the critical load of the coatings. Meanwhile, the adhered workpiece material layer is more stable on the pretreated sample irradiated at 5 mm/s. Hence, potential wear protecting properties of the in-situ formed layer can be conserved.     

TiN/Ti(C,N)涂层的显微组织与力学性能

采用磁控溅射在TNMG120408型号的硬质合金刀片上沉积了TiN/Ti(C,N)单层与多层涂层,通过XRD、SEM、纳米压痕、划痕仪与冲击测试等方法,比较分析了TiN/Ti(C,N)涂层的显微组织与力学性能。结果表明,TiN单层涂层的晶粒形貌为典型的喇叭口结构,Ti(C,N)单层涂层为平直的柱状晶结构;而TiN/Ti(C,N)多层涂层为柱状晶结构,形成了TiN、Ti(C,N)交替排列的结构。TiN与Ti(C,N)单层涂层均呈(220)生长织构,而TiN/Ti(C,N)多层涂层呈(111)生长织构。Ti(C,N)单层涂层表现出较好的硬度,而TiN/Ti(C,N)多层涂层则表现出与基体更好的结合力。     

Microstructure and properties of CVD coated on gradient cemented carbide with different WC grain size

In this paper, cemented carbides with gradient surface enriched in Co phase and depleted of cubic phases were prepared by one-step vacuum sintering. The gradient cemented carbides of different WC grain size were used as the substrates of CVD coatings. The effects of WC particle size on the formation of gradient layer, microstructure and properties of the gradient cemented carbides were investigated. Besides, the influence of WC grain size and gradient layer on microstructure, growth and adhesion strength of the coatings were studied. The results showed that the thickness of surface gradient layer decreased with increasing WC particle size, which was attributed to the decreased diffusion paths and the increased diffusion distance. The interface between the surface gradient layer and the bulk was disordered due to abnormal grain growth of WC in ultrafine cemented carbide. The microhardness across the direction of the fcc-free (Face Center Cubic Free) surface layer to the bulk were similar in the three gradient cemented carbides, and could be expressed as: from the surface to the inner, the microhardness decreased firstly, then increased sharply around the interface, and subsequently dropped to the bulk level. The coating on the fcc-free surface layer was thicker than that on bulk, and the coating on the substrate with fine-sized WC grains is the thickest. The increase of the WC grain size in the substrate could improve the bonding strength of the coating. Furthermore, the presence of Co-rich layer could improve the bonding strength. However, bonding strength was poor for the grain size of ultrafine.     

Increased adhesion of diamond-like carbon–Si coatings and its tribological properties

A pre-activation process on substrate surface has remarkably improved the poor adhesion strength of diamond-like carbon (DLC)–Si coatings on steels which is the largest obstacle in achieving a widespread application of the coatings onto machine components. The activation process consists of preliminary nitriding followed by ion etching under the selected condition. Very fine protrusions formed by the processes provide large adhesion strength to the coatings that were made continuously within the same DC-plasma-assisted chemical vapor deposition (PACVD). No intermediate layers are necessary. The critical load of DLC–Si coatings thus treated reached over 50 N in the scratch tests. The coatings with the critical load over 50 N showed much improved rolling fatigue life. The DLC–Si coating with over 50 N critical load endured a rotationa1 stress of 10⁸ cycles at a contact pressure of 3.4 GPa, whereas the DLC–Si coatings with 10 N spalled at 10⁶ cycles.     

痕法测定 TiAlN 涂层结合强度的研究

采用磁控溅射法在不锈钢表面制备了TiAlN涂层,采用压入法及划痕法表征了涂层的结合强度。分析表明,压入法只能作为一种定性的测定方法,该法测得TiAlN涂层的结合强度达到HF3。划痕法结合了声信号、摩擦力信号和划痕微观形貌,可以定量测定结合强度,该法测得在压头曲率半径为200μm的情况下,TiAlN涂层的临界载荷达到13 N,比传统TiN涂层提高了45%。     

Corrosion and Nano-mechanical Behaviors of Magnetron Sputtered Al-Mo Gradient Coated Steel

A gradient three-layer Al-Mo coating was deposited on steel using magnetron sputtering method. The corrosion and nano-mechanical properties of the coating were examined by electrochemical impedance spectroscopy and nano-indentation tests and compared with the conventional electroplated cadmium and IVD aluminum coatings. Electrochemical impedance spectroscopy was performed by immersing the coated specimens in 3.5% NaCl solution, and the impedance behavior was recorded as a function of immersion time. The mechanical properties (hardness and elastic modulus) were obtained from each indentation as a function of the penetration depth across the coating cross section. The adhesion resistance of the coatings was evaluated by scratch tests on the coated surface using nano-indentation method. The results show that the gradient Al-Mo coating exhibits better corrosion resistance than the other coatings in view of the better microstructure. The impedance results were modeled using appropriate electrical equivalent circuits for all the coated systems. The uniform, smooth and dense Al-Mo coating obtained by magnetron sputtering exhibits good adhesion with the steel substrate as per scratch test method. The poor corrosion resistance of the later coatings was shown to be due to the defects/cracks as well as the lesser adhesion of the coatings with steel. The hardness and elastic modulus of the Al-Mo coating are found to be high when compared to the other coatings.     

Au/NiCr/Ta和Au/NiCr多层金属膜的划痕特征载荷

采用摩擦力和声发射两种模式同时监测的划痕法研究了Au/NiCr/Ta和Au/NiCr多层金属薄膜的临界载荷Lc，并与TiN硬质薄膜进行了对比。实验结果表明：摩擦力和声发射模式均能反映出压头进入不同金属膜层时的变化，在单一金属薄膜层中两者均无大的变化，对应实验范围内不同的沉积温度，拐点特征载荷值基本不受其影响，而主要取决于多层膜的层厚和层数。