The Hardness of Amorphous Si-DLC Films by Molecular Dynamics Simulations

Silicon-doped diamond-like carbon （Si-DLC） films possess the potential to improve wear performance of DLC films in humid atmospheres and at higher temperatures. But many experimental results of Si-DLC films show that their structure and mechanical properties have changed greatly with the increasing silicon content. Therefore, molecular dynamics （MD） simulations were used to generate hydrogen-free Si-DLC films and study their nano-indentation process under the interaction of a diamond indenter. The results show that sp3/sp2（C） （only carbon atoms） always decreases with the increasing silicon content. But sp3/sp2（C＋Si） ratio increases firstly and reaches a maximum at the silicon content of 0.2, and then decreases with the further increase of the silicon content. Bulk modulus and hardness of the Si-DLC films both decrease with the increasing of the silicon content, which has the same trend with Papakonstantinou and Ikeyama＇s results. It is concluded that the hardness of the Si-DLC films is dependent on sp3/sp2（C）, not sp3/sp2（C＋Si）.

NANOINDENTATION OF THIN-FILM-SUBSTRATE SYSTEM DETERMINATION OF FILM HARDNESS AND YOUNG'S MODULUS

In the present paper,the hardness and Young's modulus of film-substrate systems are determined by means of nanoindentation experiments and modified models.Aluminum film and two kinds of substrates,i.e.glass and silicon,are studied.Nanoindentation XP Ⅱ and continuous stiffness mode are used during the experiments.In order to avoid the influence of the Oliver and Pharr method used in the experiments,the experiment data are analyzed with the constant Young's modulus assumption and the equal hardness assumption.The volume fraction model(CZ model)proposed by Fabes et al.(1992)is used and modified to analyze the measured hardness.The method proposed by Doerner and Nix(DN formula)(1986)is modified to analyze the measured Young's modulus.Two kinds of modified empirical formula are used to predict the present experiment results and those in the literature,which include the results of two kinds of systems,i.e.,a soft film on a hard substrate and a hard film on a soft substrate.In the modified CZ model,the indentation influence angle,(?), is considered as a relevant physical parameter,which embodies the effects of the indenter tip radius, pile-up or sink-in phenomena and deformation of film and substrate.

INVESTIGATION ON DEPOSITIONS AND HARDNESS CHARACTERISTICS OF a-SiC:H FILMS

In this paper, a deposition feature of a SiC:H films deposited by a RF sputtering system and a effect on the hardness of the films with various deposition conditions are investigated, and the effects of the silicon on a C:H are studied. It follows from the results that the properties of hardness can be changed with the depositing conditions. An increase of silane in the gas phase allows to deposit a SiC:H having tetrahedral structure. The sets of deposition conditions by which the different types of a SiC:H films can be deposited are obtained.

Deposition mechanism of nano-structured single-layered C_(36) film on a diamond (100) crystal plane

The Brenner-LJ potential is adopted to describe the interaction between C36 clusters and diamond surface, and the deposition mechanism of multi-C36 clusters on the diamond surface is also studied by using the method of molecular dynamics simulation. The simulation results show that the competition effects of two interactions, i.e. the interaction between cluster and cluster and the interaction between cluster and crystal plane, are studied, and then the influence of these competition effects on C36 cluster deposition is analysed. The finding is that when an incident energy is appropriately chosen, C36 clusters can be chemically adsorbed and deposited steadily on the diamond surface in the form of single-layer, and in the deposition process the multi-C36 clusters present a phenomenon of energy transmission. The experimental result shows that at a temperature of 300K, in order to deposit C36 clusters into a steady nanostructured single-layered film, the optimal incident energy is between 10 and 18 eV, if the incident energy is larger than 18 eV, the C36 clusters will be deposited into an island nano-structured film.

STUDY ON COMPOSITION, MICROSTRUCTURE AND HARDNESS OF DLC FILMS BY VCAD

DLC super-hard films have been deposited on the substrates of single crystalline Si, pure Ti and stainless steel 18-8 by a method of vacuum cathode arc deposition (VCAD). The composition, microstructure and micro-hardness of the films have been studied in this paper. The results indicate that hardness of the DLC films is different on the different substrates. Hardness of the films increases with decreasing in surface roughness of the films. The maximum value of micro-hardness belongs to the DLC films deposited under the hydrogen pressure of 0.35Pa and the negative bias of 100V.

DEPOSITION OF TiBN HARD FILMS ON HOT-WORKING-STEEL DIES FOR ALUMINIUM EXTRUSION VIA A DUPLEX PROCESS

Hot working steels have been used as die materials for hot extrusion of aluminium. Due to tribological interaction at elevated temperature between the die bearing and the surface of extruded aluminium profiles, not only the surface quality of the extruded product, but also the lifetime of the dies decreases. Deposition of TiBN hard films on the die bearing could improve the die performance. Treatment should be done in a duplex process process combining a plasma nitriding pretreatment (PN) and a plasma assisted chemical vapour deposition (PACVD) of TiBN. In this study the influence of the process conditions on the properties of the duplex coatings was investigated. The relationship between structure and mechanical property was researched. For testing these TIBN hard films under elevated temperature conditions and for comparison with other possible coatings special extrusion dies with different coated bearings were used. The extrusion trials were performed on the 8MN-extrusion press at the research a nd development center for extrusion, Technical University of Berlin.

Evaluation of Interfacial Adhesion Property for Thin Hard Films with Fuzzy Method

According to nanoscratch results for the TiN film, an evaluation method for interfacial fracture toughness of thin hard films is presented with fuzzy concepts, which can account for such influential factors in scratch test as surface roughness and material imperfection. Based on configuration changes in scratching curves, the parameters RV and RF are defined as the relative ratios of tip vertical displacement and of friction coefficinet. Fuzzy features of the scratching curves are analyzed carefully. The critical load is deduced from fuzzy logic operations and used to calculate the value of interfacial fracture toughness. With this method, the interfacial fracture toughness of TiN/HSS is evaluated approximately as 4.18 MPam^1/2. Results show that the method is valid and can benefit the interfacial adhesion property investigation for thin hard films.

NANOCOMPOSITE COATINGS WITH ENHANCED HARDNESS

The article reviews the present state of the art in the magnetron sputtering of hart and superhard nanocomposite coatings. It is shown that there are (1) two gr oups of hard and superhard nanocomposites: (i) nc-MN/hard phase and (ii) nc-MN/s oft phase, (2) three possible origins of the enhanced hardness: (i) dislocation- dominated plastic deformation, (ii) cohesive forces between atoms and (iii) nano structure of materials, and (3) huge differences in the microstructure of single - and two-phase films. A main attention is devoted to the formation of nanocryst alline and/or X-ray amorphous films. Such films are created in a vicinity of tra nsitions between (i) crystalline and amorphous phases, (ii) two crystalline phas es of different chemical composition or (iii) two different preferred orientatio ns of grains of the same material from which the coating is composed. The existe nce of the last transition makes it possible to explain the enhanced hardness in single-phase films. The thermal stability and oxidation resistance of hard nano composite films is also shortly discussed.

PERFORMANCE AND MICROSTRUCTURE OF SUPERHARD Si_3N_4 FILM BY HIGH POWER CO_2 LASER CVD

A superhard α-Si_3N_4 film,deposited on metal substrate,was produced by laser chemical vapor deposition adopting a kW-level high power CO_2 laser.Most films are composed of fine Si_3N_4 partieles.They join the metal substrate in strong bond.The films have super hardness,excellent resistance to wear and corrosion,etc.Their thickness may be controlled within 5-30 μm.

Stress distribution variations during nanoindentation failure of hard coatings on silicon substrates

Regarding quality inspection of technologically important nanocomposite hard coatings based on Ti,B,Si,C,and N and bioceramics such as hydroxyapatite that are used in small-scale high-precision devices and bio-implants,it is essential to study the failure mechanisms associated with nanoindentation,such as fracture,delamination,and chipping.The stress imposed by the indenter can affect the fracture morphology and the interfacial fracture energy,depending on indenter shape,substrate type,crystallographic properties,pre-existing flaws,internal microcracks,and pre-strain.Reported here are finite-element-based fracture studies that provide insights into the different cracking mechanisms related to the aforementioned failure process,showing that the fracture morphology is affected by the interaction of different cracking events.The interfacial fracture energy,toughness,and residual stress are calculated using existing models with minor adjustments,and it is found that increasing the indenter sharpness improves the shear stress distribution,making the coating more prone to separation.Depending on the prevailing type of stress,the stress distribution beneath the depression results in either crack formation or a dislocation pile-up leading to strain hardening.Different forms of resistances resulting from the indentation process are found to affect the tip–sample conduction,and because of its stronger induced plasticity than that of a Berkovich indenter tip,a sharper cube-corner tip produces more resistance.

不同摩擦副条件下二硫化钼薄膜的摩擦学性能研究

为了研究MoS_(2)-Ti薄膜与9Cr18钢、W-DLC和DLC薄膜的摩擦学行为,分别采用磁控溅射技术和等离子体增强化学气相沉积技术在9Cr18钢表面沉积了MoS_(2)-Ti薄膜、W-DLC和DLC薄膜。用扫描电子显微镜(SEM)、能量色散谱仪(EDS)和X射线衍射仪(XRD)研究了薄膜的表面形貌、化学成分和相组成。利用纳米压痕仪和球-盘摩擦试验机对不同薄膜的纳米硬度和摩擦学性能进行了分析。研究结果表明,MoS_(2)-Ti薄膜与DLC薄膜的摩擦因数和磨损率最小。相比MoS_(2)-Ti薄膜与不镀膜的9Cr18钢球摩擦副,MoS_(2)-Ti薄膜与W-DLC薄膜摩擦副的摩擦因数和磨损率没有减小。MoS_(2)-Ti薄膜与W-DLC薄膜摩擦副的磨损机制为磨粒磨损和黏着磨损,与DLC薄膜摩擦副的磨损机制为黏着磨损。摩擦副表面沉积DLC薄膜有助于降低MoS_(2)-Ti薄膜的摩擦因数和磨损率。

氧化物光学薄膜的压入硬度研究

为了评价离子源辅助对不同氧化物薄膜的影响,采用不同的镀膜设备沉积了TiO_(2)、Ta_(2)O_(5)、ZrO_(2)、SiO_(2)氧化物单层膜,用椭偏仪测量了其折射率和厚度,并用纳米压痕仪测量了不同载荷下材料的杨氏模量和纳米硬度,比较了不同离子源沉积条件下膜层这两个参数的变化。结果表明,离子源辅助能有效增加膜层杨氏模量和压入硬度,TiO_(2)增加了2 GPa,Ta_(2)O_(5)增加了4 GPa,ZrO_(2)增加了2 GPa,和膜层的折射率变化趋势是一致的。纳米压痕法也可作为评价离子源轰击能力的一种手段。

激光除漆对铝合金基材表面质量的影响

目的研究激光除漆后对铝合金基材表面阳极氧化膜的损伤情况。方法采用纳秒脉冲激光器对涂覆复合漆层的2A12铝合金表面进行激光清洗试验。采用超景深显微镜对清洗后表面形貌与横截面进行观察,利用扫描电子显微镜与能谱仪观察清洗后的微观形貌,并利用维氏硬度计对表面显微硬度进行检测。结果选择合适的激光参数能够完全除去复合漆层,当激光功率过高或激光扫描速度较低时,会发生过度清洗现象,清洗后表面的阳极氧化膜层发生损伤,甚至被去除的情况。在激光功率为450、400 W,扫描速度为4.5 mm/s时,清洗后表面的阳极氧化膜层发生破损;在激光功率为450、400 W,扫描速度为4 mm/s时,清洗后表面的阳极氧化膜层已经被去除。在激光功率为500 W,扫描速度为5.5 mm/s,与激光功率为450 W,扫描速度为5 mm/s时,完全去除复合漆层后的阳极氧化膜层表面的平均维氏硬度分别约为211HV与242HV,在工艺参数为450 W、4.5 mm/s时,表面平均维氏硬度约为168HV。结论在激光除漆的过程中,采用合适的激光工艺参数彻底去除漆层后,铝合金表面阳极氧化膜层的显微硬度并未受到影响。在发生过度清洗时,铝合金表面的阳极氧化膜层会发生烧蚀损伤以及弹性振动剥离。

氮含量对Ti-B-C-N薄膜微观结构和性能的影响

采用反应磁控溅射法在高速钢基体上制备氮原子分数分别为10.8%,15.6%,28.1%,36.4%的Ti-B-C-N薄膜,研究了氮含量对薄膜微观结构、硬度和摩擦磨损性能的影响。结果表明:Ti-B-C-N薄膜均由α-Fe和Ti(C,N)纳米晶组成,具有Ti(C,N)纳米晶镶嵌在非晶基体相中的纳米复合结构;随着氮含量增加,非晶相含量增加,Ti(C,N)纳米晶的含量和晶粒尺寸减小;随着氮含量增加,Ti-B-C-N薄膜的显微硬度增大,摩擦因数和磨损率均减小,表面磨痕变浅,磨损机制由剥落和微观犁削转变为微观抛光。

己二酸铵对铝合金硬质氧化膜性能的影响

选用2024铝合金作为基体,分别在不添加和添加己二酸铵的硫酸电解液中制备硬质氧化膜,并研究己二酸铵浓度对硬质氧化膜的微观形貌、化学成分、厚度、硬度、耐磨性能以及耐腐蚀性能的影响。结果表明:添加适量己二酸铵促进形成较致密的硬质氧化膜,并使硬质氧化膜增厚,硬度增大且耐磨性能和耐腐蚀性能明显提高。添加20 g/L己二酸铵制备的硬质氧化膜表面均匀性和致密性最好,厚度和硬度分别达到21.2μm、380.8 HV,摩擦系数和磨损失重仅为0.52和0.87 mg,并且腐蚀电流密度与铝合金基体相比降低了超过一个数量级,表现出更好的综合性能。但是添加己二酸铵并未改变硬质氧化膜的元素组成,所以硬质氧化膜的综合性能提高主要归因于添加适量己二酸铵参与了硬质氧化膜形成过程,并影响了铝离子传导过程,从而促使硬质氧化膜增厚且致密性改善。

ZL102表面阳极氧化及性能研究

选用ZL102合金作为一种新型封装基板的中间镀层进行阳极氧化试验,制备厚的多孔层阳极氧化膜。研究了电解液、电流密度、温度、时间对阳极氧化膜的形貌特征、孔隙率、厚度、硬度、耐压性和热阻性能的影响,得到了综合性能最佳的厚膜实验条件。结果表明:ZL102铝合金在不同的电解液(硫酸、硫酸-草酸、硫酸-酒石酸、硫酸-柠檬酸)、电流密度(2~6 A/dm^(2))、温度(10~30℃)、时间(80~160 min)下均能形成颜色均一、表面光滑的氧化膜。综合性能最佳的厚阳极氧化膜的工艺条件为:硫酸-草酸为电解液,电流密度6 A/dm^(2),温度15℃,时间80 min。

不同调制周期TiAlN/VN多层膜的微观结构、力学和摩擦性能研究

为了研究调制周期对TiAlN/VN纳米结构多层膜结构和性能的影响,采用射频磁控溅射的方法,制备一系列不同调制周期对TiAlN/VN纳米结构多层膜.分别利用X射线衍射仪(XRD)、场发射扫描电子显微镜(SEM)、纳米压痕仪和摩擦磨损试验机对薄膜的相结构、截面形貌、硬度和摩擦学性能进行表征.研究结果表明:TiAlN/VN多层膜始终沿(111)面择优生长.随着调制周期的增加,多层膜的硬度表现为先增加后减小,调制周期6 nm时,多层膜硬度最高,为33.12 GPa,分析认为晶格错配引发的交变应力场是多层膜出现“超硬效应”的原因.室温条件下调制周期6 nm时多层膜平均摩擦系数最小,为0.3628;高温635℃时调制周期8 nm对应的多层膜平均摩擦系数最小,为0.2485.

电弧离子镀TiN/ZrN多层膜力学性能研究

采用电弧离子镀制备了调制比和总厚度一定,周期数不同的一系列TiN/ZrN多层膜,研究了周期数对多层膜力学性能的影响。使用X射线衍射仪、扫描电子显微镜分析了多层膜的结构形貌,利用显微硬度计、往复摩擦试验机和多功能材料表面性能试验仪测试了薄膜的力学性能和摩擦学性能。结果表明,多层膜都呈现单一的面心立方结构,以柱状晶结构生长,表面致密光滑,界面效应明显,力学性能受到界面结构和择优取向的影响,当周期数为50时,TiN具有明显的(200)择优取向,多层膜的硬度达到最大值2568 Hv,多层膜的摩擦学性能受到表面形貌和硬度的影响,当周期数为40时,具有最低的摩擦系数为0.47,磨损率随着硬度的增加而减少,在50周期时的磨损率为6.9×10^(-6)mm^(3)·N^(-1)·m^(-1),耐磨性最佳。

硬度法测量铝合金阳极氧化膜附着力

铝合金阳极氧化膜的表面膜状结构特殊,目前没有合适的定量方法表征其附着力。利用维氏硬度计对阳极氧化膜进行矩阵化打点,控制压痕间距,利用压痕之间的挤压作用使氧化膜脱落;根据压痕交界处的氧化膜脱落情况定量评价阳极氧化膜的附着力水平;同时,制定了铝合金阳极氧化膜附着力的评价等级分类方法,将铝合金阳极氧化膜附着力水平分为0~5级。