脉冲偏压对PECVD制备DLC薄膜的结构及性能的影响

在不锈钢基材表面利用等离子体增强化学气相沉积技术(PECVD)改变脉冲偏压制备不同结构类金刚石薄膜(DLC)。分别采用表面轮廓仪、扫描电镜、拉曼光谱及电子探针分析薄膜的表面粗糙度、断面形貌、薄膜结构及成分,采用纳米压痕仪及划痕仪测试薄膜的纳米硬度、弹性模量和膜基结合力,采用球盘摩擦试验机测试薄膜在大气环境中的摩擦学性能。结果表明:脉冲偏压显著影响PECVD制备的DLC薄膜的表面粗糙度、微观形貌、膜基结合力、纳米硬度及摩擦学性能;随偏压的增大,DLC薄膜的表面粗糙度,摩擦因数及磨损量都先减小后增大,而膜基结合力则先增大后减小。其中2.0 k V偏压制备的DLC薄膜具有最强的膜基结合力,而1.6 k V偏压制备的DLC薄膜具有最低的表面粗糙度、最高的硬度和最优的减摩耐磨性能。     

Ti表面高承载摩擦学SiC薄膜的研究

采用室温磁控溅射技术在金属钛表面制备出碳化硅(SiC)薄膜。研究了SiC薄膜的组织结构、纳米压痕行为和摩擦磨损性能。实验结果表明:SiC薄膜呈非晶态,含有较多Si-C键;膜-基间结合很好,具有明显的且呈梯度的相互元素扩散;薄膜的硬度(H)为12.1 GPa,杨氏弹性模量(E)为166.2 GPa,硬度与弹性模量比值(H/E)为0.073;在以氮化硅球为对摩件,初始Hertzian接触应力约为685~930 MPa的室温Kokubo人体模拟体液条件下,其磨损速率在10-5 mm3/Nm级,摩擦系数约为0.215,且不出现薄膜的破裂及剥落现象。分析表明,该薄膜在高载荷下仍具有很好的摩擦磨损性能,其原因是薄膜具有高的韧性和很好的界面结合;高的韧性与H及H/E相对较低有关,而好的界面结合与膜-基间弹性模量的差值较小有关。     

磁控溅射沉积TiB_2/DLC纳米多层膜的结构及其机械性能研究

采用非平衡磁控溅射系统在P(100)硅片和304不锈钢基底上制备TiB_2/DLC纳米多层膜。利用FESEM、TEM、XRD和AFM观察多层膜的微观结构和表面形貌;利用纳米压痕仪、维氏硬度计和CSM球-盘摩擦磨损试验机考察TiB_2靶电流对多层膜的机械性能和摩擦学性能的影响。结果表明:TiB_2/DLC多层膜具有良好的多层调制结构,多层膜沿TiB_2(101)晶向择优生长;多层膜的表面粗糙度随着TiB_2靶电流增加而增加;多层膜中的大量异质界面能显著提高薄膜的硬度及韧性,而且当TiB_2靶电流为2.0 A时,多层膜的硬度约为单层DLC薄膜的两倍;多层膜中具有硬质TiB_2层和软质DLC层的交替结构,在摩擦过程中,硬层TiB_2起到良好的承载作用,软层DLC起到良好的润滑作用,使多层膜具有比单层DLC薄膜更低的摩擦因数。     

纺织机钢丝圈表面类金刚石膜的制备及摩擦特性研究

为提高纺织机高速纺纱工况下钢丝圈表面的磨损性能,采用直流等离子气相沉积法在钢丝圈表面制备类金刚石涂层(DLC),采用原位扫描探针显微镜观测涂层表面形貌,测量并计算涂层硬度。结果发现,DLC涂层颗粒粒径约为100 nm,呈岛状聚集分布,硬度约为18 GPa。采用球-盘式摩擦试验机研究DLC涂层在不同载荷(20~100 N)和不同转速(100~600 r/min)条件下的摩擦特性。结果表明,在低载高速的条件下,DLC涂层具有良好的耐磨特性,符合钢丝圈的实际工况。采用傅里叶变换红外光谱分析涂层的磨损机制,结果发现,在摩擦磨损过程中从薄膜中释放出来的氢和涂层的剪切变形引起了DLC薄膜的石墨化SP^3/SP^2转变,从而降低了摩擦因数和磨损率。     

轮胎模具DLC涂层摩擦学性能研究

为了探究高性能轮胎模具DLC涂层的应用前景,提升轮胎模具耐磨减摩性,采用化学气相沉积法在35#钢基体上制备了厚约1.6μm的DLC涂层,利用SEM、AFM、Raman光谱仪、纳米压痕仪、端面摩擦磨损试验机对DLC涂层的表面微观结构和摩擦学性能进行了研究,试验及测试结果表明,用化学气相沉积法制备的DLC涂层表面光滑致密,颗粒细小均匀,粗糙度小;DLC涂层具有极好的抗磨减摩特性,比35#钢耐磨,纳米硬度和弹性模量高达20.27 GPa和184.63 GPa;在140℃高温条件下,摩擦系数低至0.454 4。DLC涂层优异的抗磨减摩特性可有效提高轮胎模具的工作性能-抗粘胶、易脱模、寿命长,为制造高性能DLC轮胎模具提供摩擦学方面理论依据。     

CrSiCN薄膜的力学性能及水润滑特性研究

运用非平衡磁控溅射技术,通过改变硅烷的流量,在Si(100)和316L不锈钢片基材上沉积不同元素含量的CrSiCN四元薄膜;运用X射线衍射仪、扫描电子显微镜和纳米压痕仪分别研究薄膜的结构、表面形貌和纳米硬度;运用球-盘摩擦磨损试验机研究水润滑下CrSiCN薄膜与Al_2O_3小球对摩的摩擦学特性。结果表明:由于固溶强化和纳米复合结构的形成,CrSiCN薄膜在硅烷流量为10 sccm获得最大硬度19.3 GPa和最大弹性模量306.9 GPa,继续增加硅烷流量,由于薄膜结构向非晶态转变,薄膜硬度降低;硅烷流量为10 sccm得到的薄膜CrSiCN具有最低的摩擦因数0.24,随着硅烷流量的增加,由于硬度的降低和过量非晶相的形成,薄膜抗磨性能降低,摩擦因数波动较大。     

铝掺杂类石墨薄膜的构筑及其摩擦学性能研究

利用磁控溅射技术在硅片表面上制备铝掺杂类石墨(Graphite-like carbon,GLC)薄膜,采用原子力显微镜、场发射扫描电镜、X射线光电子能谱仪、纳米压痕仪等考察铝掺杂对薄膜表面形貌、结构及其机械性能的影响规律;利用旋转的球一盘微摩擦试验机考察薄膜的摩擦行为.结果表明:铝的引入使GLC薄膜表面更加平整、致密;GLC薄膜的硬度和弹性模量随着掺铝量的增加而增加;低载低速时,薄膜摩擦因数随着铝含量的增加而增加,高载高速时,摩擦因数随铝掺入量的增加明显降低且更稳定.     

射频磁控溅射法制备MoS2/SiC双层薄膜

采用射频磁控溅射法在室温、500℃的单晶硅和GCr15钢基体上制备了MoS2/SiC双层薄膜,并借助X射线衍射仪、扫描电子显微镜、摩擦磨损试验机以及划痕仪等研究了薄膜的结构、形貌、成分、摩擦学性能以及薄膜与基体的结合力。结果表明:当衬底温度为500℃时制备的MoS2/SiC双层薄膜表面致密平整,两层薄膜之间界面平直,膜厚约为0.8μm;该双层膜的摩擦因数低,耐磨性好;添加中间层可提高薄膜与基体的结合力。     

纳米结构碳基薄膜的制备及性能研究

利用单极脉冲等离子体增强化学气相沉积技术在单晶硅衬底上沉积含氢碳薄膜,用高分辨透射电子显微镜和激光拉曼光谱仪研究薄膜的微观结构,用X射线光电子能谱分析薄膜的化学键状态,并用纳米压痕仪测定薄膜的硬度和弹性模量,在CSM往复式摩擦磨损试验机上考察薄膜的摩擦学性能。结果表明:在单极脉冲等离子体增强化学气相沉积系统上成功制备出在非晶基体上镶嵌弯曲类富勒烯纳米结构的含氢碳薄膜,其独特的类富勒烯纳米结构赋予薄膜良好的力学性能,其弹性恢复系数和硬度分别高达86%和26.37 GPa;与非晶结构薄膜相比,制备的纳米结构含氢碳薄膜在室温环境下摩擦学性能更为优异,在机械摩擦表面具有广阔的应用前景。     

应用纳米压痕法测试类金刚石薄膜的力学性能

纳米压痕仪被称为材料机械性质微探针,它借助于加载-卸载过程中压痕对载荷和压入深度的敏感关系,使得测试始终在薄膜材料的弹性限度内,克服了维氏法和努氏法等传统方法引起压痕边缘模糊或者碎裂的缺点,从而正确地、可靠地测试出薄膜材料的硬度和弹性模量等纳米力学性能.试验用微波电子回旋共振等离子体增强化学气相沉积技术,在不同偏压条件下制备三种类金刚石薄膜(DLC膜),用纳米压痕仪测试不同载荷下薄膜的硬度和弹性模量值.试验结果表明,材料的纳米硬度和弹性模量随着载荷的增大而逐渐减小.     

Tribological Performance of Diamond and Diamondlike Carbon Films at Elevated Temperatures

In this study, the authors investigated the tribological performance of diamond and diamondlike carbon (DLC) films as a function of temperature. Both films were deposited on silicon carbide (SiC) by microwave plasma chemical vapor deposition and ion-beam deposition processes. Tribological tests were performed on a reciprocating wear machine in open air (20 to 30% relative humidity) and under a 10 N load using SiC pins. For the test conditions explored, the steady-state friction coefficients of test pairs without a diamond or DLC film were 0.7 to 0.9 and the average wear rates of pins were 10^?5 to 10^?7 mm³/N·m, depending on ambient temperature. DLC films reduced the steady-slate friction coefficients of the test pairs by factors of three to five and the wear rates of pins by two to three orders of magnitude. Low friction coefficients were also obtained with the diamond films, but wear rates of the counterface pins were high due to the very abrasive nature of these films. The wear of SiC disks coated with either diamond or DLC films was virtually unmeasurable while the wear of uncoated disks was substantial. Test results showed that the DLC films could afford low friction up to about 300° C. At higher temperatures, the DLC films graphitized and were removed from the surface. The diamond films could withstand much higher tempera-lures, but their tribological behavior degraded. Raman spectroscopy and scanning electron microscopy were used to elucidate the friction and wear mechanisms of both films at high temperatures.     

Atomistic Insights into the Running-in,Lubrication, and Failure of Hydrogenated Diamond-Like Carbon Coatings

The tribological performance of hydrogenated diamond-like carbon (DLC) coatings is studied by molecular dynamics simulations employing a screened reactive bond-order potential that has been adjusted to reliably describe bond-breaking under shear. Two types of DLC films are grown by CH₂ deposition on an amorphous substrate with 45 and 60 eV impact energy resulting in 45 and 30% H content as well as 50 and 30% sp³ hybridization of the final films, respectively. By combining two equivalent realizations for both impact energies, a hydrogen-depleted and a hydrogen-rich tribo-contact is formed and studied for a realistic sliding speed of 20 m s⁻¹ and loads of 1 and 5 GPa. While the hydrogen-rich system shows a pronounced drop of the friction coefficient for both loads, the hydrogen-depleted system exhibits such kind of running-in for 1 GPa, only. Chemical passivation of the DLC/DLC interface explains this running-in behavior. Fluctuations in the friction coefficient occurring at the higher load can be traced back to a cold welding of the DLC/DLC tribo-surfaces, leading to the formation of a transfer film (transferred from one DLC partner to the other) and the establishment of a new tribo-interface with a low friction coefficient. The presence of a hexadecane lubricant leads to low friction coefficients without any running-in for low loads. At 10 GPa load, the lubricant starts to degenerate resulting in enhanced friction.     

Friction and wear behaviour of hard and superhard coatings at cryogenic temperatures

The work presents data on friction and wear behaviour of pin-on-disc pairs with superhard diamond-like carbon (DLC) coatings and hard coatings of zirconium nitride (ZrN) and titanium nitride (TiN) in liquid nitrogen with loads of 2.5 and 10 N and sliding speed of 0.06 m/s. It is shown that at cryogenic temperatures the friction coefficients of pairs of two types of DLC coatings obtained by vacuum-arc deposition of filtered high-speed carbon plasma fluxes depend to a great deal on the mechanical properties of the coatings defined by predominant sp² or sp³ hybridization of valence electrons. A friction coefficient of 0.76 was observed for friction pairs of superhard (90 GPa) DLC coatings having properties similar to those of diamond. For “softer” DLC coatings of 40 GPa and properties similar to those of graphite the friction coefficient shows lower values (0.24–0.48) dependent on normal load and counterbody material. The DLC coatings obtained by the filtered arc technology exhibit good wear resistance and have strong adhesion to the substrate under friction in liquid nitrogen. With a normal load of 10 N under cryogenic temperature a low wear rate (of the order of 7.2×10⁻⁴ nm/cycle) was found for superhard DLC coatings. The friction coefficient of pairs with hard ZrN and superhard DLC coatings on steel discs was revealed to be linearly dependent on the counterbody material hardness between 20 and 100 GPa. The hardness of the pin was varied by means of depositing TiN or DLC coatings and also by using high-hardness compounds (boron nitride and synthetic diamond). Proceeding this way can be promising since it offers the possibility of creating low-temperature junctions of required friction properties.     

Tribological Properties of Diamond-Like Carbon Films in Low and High Moist Air

Diamond-like carbon (DLC) film was deposited on Si wafer by a plasma CVD deposition system using benzene. Tribological properties of the DLC film were evaluated using a ball-on-disk tribo-meter in low (RH 1720 %) and high humidity (RH 9095 %) conditions in air. The effect of sliding speed (4.2 mm/s to 25 mm/s) and load (1.06 N to 3.08 N) on friction and wear was investigated. The friction behavior of the DLC film was obviously different in low and high humidity. When tested under low humidity conditions, the friction coefficient decreased significantly with increasing speed, and increased with load. However, under high humidity conditions, the friction coefficient increased with the speed and decreased with increasing load. The wear of the DLC film was little influenced by the sliding speed, normal load and humidity; a level of 10^-8 mm³/Nm could be obtained in all tests. The formation of a uniform transfer layer would be the main factor which controlled the friction coefficient of the DLC films. Unlike the friction, the wear resistance of the DLC film is not so easy to discuss and may be affected mainly by the tribo-chemical reaction in all the test conditions.     

Boundary Lubrication Properties of Nanoperiod Solid Lubricant Multilayer Films Composed of Diamond-Like Carbon and Gold Layers

To develop electroconductive and high-endurance solid lubricant nanoperiod multilayer (DLC/Au)_n films, diamond-like carbon (DLC) and gold layers were deposited while controlling the time the substrate was exposed graphite and gold targets. The electrical resistivity of the (DLC/Au)_n multilayer films was ~12.4 Ω cm. The hardness of the (DLC/Au)_n multilayer films was similar to that of DLC films and much higher than that of gold monolayer films. According to the results of oscillating sliding tests under water boundary lubrication and dry conditions, (DLC/Au)_n multilayer films exhibited the low friction coefficient, little damage, and high sliding durability than the monolayer films. (DLC/Au)_n films also have a lower friction coefficient and exhibit less damage than a Au monolayer under polyalphaolefin boundary lubrication.     

Small amplitude reciprocating wear performance of diamond-like carbon films: dependence of film composition and counterface material

Small amplitude (50 μm) reciprocating wear of hydrogen-containing diamond-like carbon (DLC) films of different compositions has been examined against silicon nitride and polymethyl-methacrylate (PMMA) counter-surfaces, and compared with the performance of an uncoated steel substrate. Three films were studied: a DLC film of conventional composition, a fluorine-containing DLC film (F-DLC), and silicon-containing DLC film. The films were deposited on steel substrates from plasmas of organic precursor gases using the Plasma Immersion Ion Implantation and Deposition (PIIID) process, which allows for the non-line-of-sight deposition of films with tailored compositions. The amplitude of the resistive frictional force during the reciprocating wear experiments was monitored in situ, and the magnitude of film damage due to wear was evaluated using optical microscopy, optical profilometry, and atomic force microscopy. Wear debris was analyzed using scanning electron microscopy and energy dispersive spectroscopy. In terms of friction, the DLC and silicon-containing DLC films performed exceptionally well, showing friction coefficients less than 0.1 for both PMMA and silicon nitride counter-surfaces. DLC and silicon-containing DLC films also showed significant reductions in transfer of PMMA compared with the uncoated steel. The softer F-DLC film performed similarly well against PMMA, but against silicon nitride, friction displayed nearly periodic variations indicative of cyclic adhesion and release of worn film material during the wear process. The results demonstrate that the PIIID films achieve the well-known advantageous performance of other DLC films, and furthermore that the film performance can be significantly affected by the addition of dopants. In addition to the well-established reduction of friction and wear that DLC films generally provide, we show here that another property, low adhesiveness with PMMA, is another significant benefit in the use of DLC films.     

Friction and wear of diamondlike carbon on fine-graindiamond

Friction and wear behavior of ion-beam-deposited diamondlikecarbon (DLC) films coated on chemical-vapor-deposited (CVD),fine-grain diamond coatings were examined in ultrahigh vacuum,dry nitrogen, and humid air environments. The DLC films wereproduced by the direct impact of an ion beam (composed of a 3 :17 mixture of Ar and CH₄) at ion energies of 1500 and700 eV. Sliding friction experiments were conducted withhemispherical CVD diamond pins sliding on four differentcarbon-base coating systems: DLC films on CVD diamond; DLC filmson silicon; as-deposited, fine-grain CVD diamond; andcarbon-ion-implanted, fine-grain CVD diamond on silicon. Resultsindicate that in ultrahigh vacuum theion-beam-deposited DLC films on fine-grain CVD diamond (similarto the ion-implanted CVD diamond) greatly decrease both thefriction and wear of fine-grain CVD diamond films and providesolid lubrication. In dry nitrogen and in humid air,ion-beam-deposited DLC films on fine-grain CVD diamond films alsohad a lowsteady-state coefficient of friction and a low wear rate. Thesetribological performance benefits, coupled with a wider range ofcoating thicknesses, led to longer endurance life and improvedwear resistance for the DLC deposited on fine-grain CVD diamondin comparison to the ion-implanted diamond films. Thus, DLCdeposited on fine-grain CVD diamond films can be an effectivewear-resistant, lubricating coating regardless of environment.     

Molecular dynamics simulations of atomic-scale tribology between amorphous DLC and Si-DLC films

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 structures and tribological properties changed greatly with silicon content. Therefore, molecular dynamics (MD) simulations were used to study the sliding friction process between DLC and Si-DLC films on un-lubricated boundary condition. The results show that a part of sp² bonding of the Si-DLC films is converted into sp³ bonding with the addition of silicon atoms, and the sp³/sp² ratio increases with the increase in silicon content. A transfer film between the DLC and Si-DLC films is formed and the friction force changes with the silicon content. Moreover, the simulations have showed that the silicon addition promotes the bonding of interfilms being formed.     

Friction of diamond-like carbon films in different atmospheres

Diamond-like carbon (DLC) films constitute a class of new materials with a wide range of compositions, properties, and performance. In particular, the tribological properties of these films are rather intriguing and can be strongly influenced by the test conditions and environment. In this paper, a series of model experiments are performed in high vacuum and with various added gases to elucidate the influence of different test environments on the tribological behavior of three DLC films. Specifically, the behavior of a hydrogen-free film produced by a cathodic arc process and two highly hydrogenated films produced by plasma-enhanced chemical-vapor deposition were studied. Flats and balls used in these experiments were coated with DLC and tested in a pin-on-disc machine under a load of 1 N and at constant rotational frequency. With a low background pressure, in the 10⁻⁶ Pa range, the highly hydrogenated films exhibited a friction coefficient of less than 0.01, whereas the hydrogen-free film gave a friction coefficient of approximately 0.6. Adding oxygen or hydrogen to the experimental environment changed the friction to some extent. However, admission of water vapor into the test chamber caused large changes: the friction coefficient decreased drastically for the hydrogen-free DLC film, whereas it increased slightly for one of the highly hydrogenated films. These results indicate that water molecules play a prominent role in the frictional behavior of DLC films—most notably for hydrogen-free films but also for highly hydrogenated films.