基于工艺控制与基体处理的类金刚石涂层性能优化技术研究综述*

类金刚石涂层(DLC)因其高硬度、高耐磨性、低摩擦因数等特性被广泛用作机械零部件润滑防护涂层,但传统的DLC涂层在高速、重载及高温等苛刻工况下易发生摩擦因数升高、开裂及鼓包/起皮并从基材脱落进而导致涂层润滑防护失效。基于工艺控制及基体处理2个方面,从涂层的沉积工艺、元素掺杂、过渡层的添加及渗氮渗碳、改变粗糙度、加工表面微织构等手段对提升DLC涂层服役性能的优化措施进行综述;针对提高DLC涂层服役性能的措施进行理论分析,并提出未来的研究方向,如建立规范统一的高性能DLC涂层的制备工艺及性能表征方法,进一步探讨不同基体粗糙度对涂层机械啮合力的影响,以及微织构的尺寸效应及对DLC涂层的热应力缓释作用。     

凸轮挺柱摩擦副接触应力的仿真计算

采用柔性动力学方法分析凸轮挺柱摩擦副的性质,并以运动传动知识和Matalab软件分析了气门的运动学和动力学性质。通过运动学和动力学结果的对比可知,运用动力学模型得到的凸轮挺柱间接触力和接触应力的结果大于运动学模型得到的结果,配气机构的弹性变形会使凸轮挺柱摩擦表面承受更大的接触应力。     

空间飞轮轴承DLC涂层表面改性的工艺研究

使用类金刚石薄膜(Diamond Like Carbon,DLC)作为涂层,采用等离子体离子浸没注入技术Plasma Immersion Ion Implantation and Deposition,PIIID)对空间飞轮长寿命轴承沟道表面进行改性。结果表明,陪试件表面DLC改性后表面粗糙度、轴承内外沟道轮廓形状误差等特性未发生明显改变,改性层表面纳米硬度提高2倍左右;陪试件摩擦试验结果表明,改性后表面的摩擦学性能得到了明显改善;DLC涂层的稳定摩擦因数仅为基体的1/3～1/4,有利于延长空间飞轮轴承的工作寿命。     

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。     

超音速火焰喷涂锡青铜-钢基双金属材料摩擦性能

采用超音速火焰喷涂QWFSn8Zn3粉末制备钢背双金属材料。研究不同润滑介质、不同表面粗糙度和不同摩擦载荷对超音速喷涂锡青铜-钢基涂层摩擦性能的影响。分析锡青铜涂层的磨损形貌和磨损机制。研究结果表明:抗磨液压油润滑条件下,涂层有最小的摩擦因数0.093,30#润滑油、液体石蜡和固体MoS2润滑下涂层摩擦因数分别为0.099、0.107和0.099;随表面粗糙度减小,喷涂锡青铜-钢基涂层摩擦因数逐渐减小;随着摩擦载荷的增加,喷涂层摩擦因数逐渐减小;不同润滑介质条件下,涂层存在磨粒磨损、黏着磨损和疲劳磨损共同作用的磨损机制。     

润滑油缺失工况下不同活塞环涂层对缸套摩擦磨损对比研究

为研究润滑油缺失工况下不同活塞环涂层在不同温度下与缸套的摩擦学性能,选取5种商用活塞环涂层,利用扫描电子显微镜观察不同涂层的截面形貌,利用往复式摩擦磨损试验机,在润滑油缺失工况下,分别在常温、200 ℃和350 ℃条件下进行摩擦磨损试验,利用轮廓仪和光学显微镜分别观察摩擦试验后的磨损量和磨痕形貌。结果表明：CrN基涂层和CKS涂层主要为黏着磨损,对缸套磨损大,不同温度下摩擦学性能稳定;含DLC涂层主要为磨料磨损,常温摩擦因数小,高温下不同涂层有较大差异,其中CDC+DLC涂层综合性能最佳。     

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。     

沉积温度对脉冲真空弧源沉积类金刚石薄膜性能的影响

利用脉冲真空弧源沉积技术在Cr17Ni14Cu4不锈钢和Si(100)基体上制备了类金刚石(DLC)薄膜,研究了基体沉积温度对DLC薄膜的性能和结构的影响。研究表明,随着沉积温度由100 ℃提高到400 ℃,DLC薄膜中sp3 键质量分数减少,sp2键质量分数增多,薄膜复合硬度逐渐降低。当DLC薄膜沉积温度达到400 ℃时,薄膜中C原子主要以sp2键形式存在,与沉积温度为100 ℃时制备的DLC薄膜相比,薄膜复合硬度降低50%。DLC薄膜具有优异的耐磨性,摩擦因数低,随着沉积温度由100 ℃提高到400 ℃,Cr17Ni14Cu4不锈钢表面沉积的DLC薄膜耐磨性降低。沉积温度为100 ℃时,Cr17Ni14Cu4不锈钢表面沉积的DLC薄膜后,耐磨性大幅度提高。DLC薄膜与不锈钢基体结合牢固。     

偶件表面粗糙度对PTFE材料摩擦磨损性能的影响

为了研究干摩擦条件下偶件表面粗糙度对聚四氟乙烯(PTFE)密封材料摩擦磨损性能的影响,利用MMW-1立式万能摩擦磨损试验机,在不同载荷和转速下研究由PTFE材料制作的试验环分别与316L不锈钢和45#钢配副时的摩擦磨损性能,并利用粒形分析仪对PTFE试验环试验前后端面的形貌进行观测;利用触针式轮廓仪对摩擦配副钢环的端面粗糙度进行精确测量,分析表面粗糙度对PTFE试验环摩擦磨损性能的影响。试验结果表明:在干摩擦条件下,摩擦配副钢环的表面粗糙度过高或者过低都会引起PTFE试验环磨损量的增加;定载荷时,PTFE试验环磨损量随摩擦配副钢环表面粗糙度的增大先减小后增大,随转速的增大而增大;定转速时,PTFE试验环摩擦因数随摩擦配副钢环表面粗糙度的增大稍减小后而后增大,随载荷的增大先减小后增大;在相同工况下,316L不锈钢对PTFE试验环的切削和犁沟作用比45#钢更加明显。     

掺杂碳基涂层抗摩耐磨性能的改进

<正>在苛刻的工作条件下,涂层技术可以减小摩擦和提高零部件的耐磨性,因此成为减少CO_2排放的途径之一,在汽车行业得到了广泛的应用。为了适应当前提高工作温度和降低润滑油粘度的发展趋势,豪泽(Hauzer)公司开始对类金刚石(DLC)涂层掺杂技术和ta-C(四面体非晶碳)涂层进行研究。不同的掺杂材料被添加到无氢和有氢DLC涂层之中。     

Valvetrain Friction Reduction through Thin Film Coatings and Polishing

In a direct-acting mechanical bucket tappet–type valvetrain, the cam and tappet contact is responsible for about 85% of the total valvetrain frictional losses. Because this contact operates primarily in a mixed lubrication regime, it offers an opportunity for friction reduction through surface engineering. The friction reduction potential of thin Mn-phosphate coating, diamond-like carbon coating, and polishing on the bucket surface was explored using a motored valvetrain rig equipped with 3.5L V6 engine head. The durability of tappets and cam lobes was also evaluated using a different motored valvetrain rig consisting of a single lobe and a single tappet. The polished buckets demonstrated substantial friction benefit over current production buckets at all speeds investigated. The diamond-like carbon coated buckets did not show any additional friction reduction benefit. The wear data demonstrated much less wear with polished buckets and also for cam lobes when in contact with polished buckets compared to current production buckets and cam lobes. The composition of antiwear surface films on polished buckets was found to be similar to that on current production buckets.     

The effects of contact configuration and coating morphology on the tribological behaviour of tetrahedral amorphous diamond-like carbon (ta-C DLC) coatings under boundary lubrication

ABSTRACT

Tribological studies were carried out with tetrahedral amorphous diamond-like carbon (ta-C DLC) coatings, varying in thickness and roughness, using two different contact configurations lubricated with seven types of hydraulic oils. Tribopair of cast iron and ta-C coated steel were tested in both non-conformal and conformal, unidirectional sliding contacts. The friction and wear results were mainly affected by the thickness of the coating in the non-conformal contact and the surface roughness of the coating in the conformal contact. Tests done with mineral base oil containing rust inhibitor in the non-conformal contact and with Polyalphaolefins and synthetic ester base oils in the conformal contact resulted in the lowest friction while that with mineral base oil containing zinc resulted in high friction and counterface wear. The results highlight the interdependence of contact configuration, lubricant chemistry, coating’s surface morphology and coating’s thickness in determining the tribological behaviour of ta-C coatings under boundary lubrication.     

Tribological Dependence of the High-Performance Ferrous-Based Coating on Different Coating Counterparts in Engine Oil

A ferrous-based coating with significant chromium was fabricated on aluminum alloy substrate using a plasma spray technique. The tribological performance of the as-fabricated ferrous-based coating sliding against different coatings including Cr, CrN, TiN, and diamond-like carbon (DLC) in an engine oil environment were comparatively studied. Results showed that the high hardness of the sprayed ferrous-based coating was achieved due to the dispersion strengthening effect of Cr₇C₃ phase embedded in the austenite matrix. The ferrous-based coating exhibited low friction coefficients when coupled with these four coating counterparts, which could be attributed to the boundary lubricating effect of engine oil. However, both friction and wear of the ferrous-based coating were different when sliding against these different coating counterparts, which might be closely related to the surface roughness, self-lubricating effect, and mechanical properties of the coupled coatings. Ferrous-based coating sliding against CrN and DLC coatings exhibited good tribological performance in engine oil. The best coating counterpart for the ferrous-based coating in an engine was DLC coating.     

表面粗糙度对配流副润滑特性的影响

为研究表面粗糙度对轴向液压柱塞泵马达配流副润滑特性的影响,引入Weierstrass-Mandelbort分形函数,对不同幅值的表面粗糙度的表面形貌进行二维和三维模拟,建立考虑表面粗糙度的流固热耦合下的配流副油膜润滑模型,采用中差分形式的有限差分法和松弛迭代法对其进行数值求解,并分析油膜厚度、油膜压力、油膜承载力、摩擦因数等性能参数随着表面粗糙度幅值变化的规律。通过盘-盘形式的配流盘-缸体摩擦磨损试验,得到不同幅值的表面粗糙度下配流副摩擦因数,对所建立的数学模型进行验证。数值计算结果表明,表面粗糙度幅值的增大会引起油膜承载力增大,但也会引起最大油膜压力和摩擦因数的增大,导致摩擦性能下降。摩擦磨损试验发现,表面粗糙度增大,配流盘表面摩擦磨损情况加剧,配流副润滑性能和耐磨性能整体降低。因此在配流盘表面加工处理中,应适当降低其表面粗糙度。     

Novel method of measuring tappet rotation and the effect of lubricant rheology

One of the main drivers for developing lubricant technology is engine durability. Researchers and scientists are using new technologies, materials and advanced lubricant formulations to reduce overall engine friction and wear. One of the main engine tribological components is the valve train. This is one of the most challenging components to lubricate effectively because of the higher contact loadings and accounts for 10–20% of the total engine friction loss. The two main factors affecting the performance of engine valve trains are wear and friction, and a wide range of mechanical configurations are used to improve these. For example, direct-acting overhead camshaft valve train configurations use a rotating tappet design. Normally, the tappet is slightly offset from the cams and the cam is slightly conical to match the domed tappet to facilitate tappet rotation for even wear and to reduce slippage. In this paper, a novel innovative technique has been described to monitor tappet rotation in a real production engine having a direct overhead cam–tappet arrangement. The monitoring technique was applied to a VW Tdi engine head, and tests were carried out under different operating conditions. Lubricant compositions, oil temperature, pressure and camshaft speeds on tappet rotation were measured and all are shown to have an effect. The balance of forces between the cam–tappet and tappet-bore was found to be interlinked and the design of the hydraulic lash adjuster had a significant effect.This unique tappet rotation monitoring system can be used on most of the direct overhead camshaft engines, with minor engine modifications, to measure lubricant and hardware effects under both motored and fired conditions.     

Influence of different surface modification technologies on friction of conformal tribopair in mixed and boundary lubrication regimes

Moving machine assemblies are generally designed to operate in full film lubrication regime to ensure high efficiency and durability of components. However, it is not always possible to ensure this owing to changes in operating conditions such as load, speed, and temperature. The overall frictional losses in machines are dependent on the operating lubrication regimes (boundary, mixed or full-film). The present work is thus aimed at investigating the role of different surface modification technologies on friction of a sliding bearing/roller tribopair both in boundary and mixed lubrication regimes. A special test rig comprising of two bearings was built for the experimental studies. Tribological tests were conducted in a wide speed range to enable studies in boundary and mixed lubrication regimes. The influence of application of different surface modification technologies on both the sliding bearing and the roller surfaces on friction has been studied. The rollers used in these studies were provided with five different coatings (hard DLCs and a soft self-lubricating coating). Additionally, two uncoated rollers having different surface roughness were also studied. Uncoated bearings were used in all tribopairs except two. These two bearings were coated with DLC and phosphate coatings respectively and uncoated rollers were the mating counterparts. Friction measurements were made on the new as well as the previously run-in surfaces. It was found that the rollers with self-lubricating coating resulted in lowest boundary friction closely followed by the rollers with the hardest DLC coatings. The DLC coating applied on to the bearing showed lower boundary friction after running-in. Mixed friction has been found to be mainly dependent on the surface topography characteristics of both the original and the run-in surfaces of bearings and rollers. The harder DLC coatings and the phosphated bearing showed the lowest mixed friction due to an efficient running-in of the bearing surface.     

A study of the measurement of surface temperature at a cam/tappet contact

Cam/tappet wear is one of the most difficult reliability and durability problems to predict during the development of a prototype engine valve‐train system. In the present study, the cam/tappet surface temperature was measured and calculated to determine the effect of surface temperature on the lubricating conditions at a cam/tappet contact. The measurement method, sometimes called the dynamic thermocouple technique, was based on the Seebeck effect: by using different materials for the cam and tappet, the cam/tappet contact point becomes the hot junction of a ‘thermocouple’. The cam/tappet contact surface temperature can therefore be measured continuously. The measured temperature results show good agreement with predictions. Temperature spikes, however, were not found in the test using new oil, but were shown by the theoretical model. Such results indicate that the cam/tappet interface operates in effective lubricating conditions, even when the oil temperature is relatively high. Further research with degraded oil supplied at high temperature is needed for a thorough understanding of abnormal cam wear.     

Synergistic effect between nano-ceramic lubricating additives and electroless deposited Ni-W-P coating

The major solving ways for the material wear are surface modification and lubrication.Currently,the researches at home and abroad are all limited to the single study of either nano-lubricating oil additive or electroless deposited coating.The surface coating has high hardness and high wear resistance,however,the friction reduction performance of the coating with high hardness is not good,the thickness of the coating is limited,and the coating can not regenerate after wearing.The nano-lubricating additives have good tribological performance and self-repair function,but under heavy load,the self-repair rate to the worn surface with the nano-additives is smaller than the wearing rate of the friction pair.To solve the above problems,the Ni-W-P alloy coating and deposition process with excellent anti-wear,and suitable for industrial application were developed,the optimum bath composition and process can be obtained by studying the influence of the bath composition,temperature and PH value to the deposition rate and the plating solution stability.The tribological properties as well as anti-wear and friction reduction mechanism of wear self-repair nano-ceramic lubricating additives are also studied.The ring-block abrasion testing machine and energy dispersive spectrometer are used to explore the internal relation between the coating and the nano-lubricating oil additives,and the tribology mechanism,to seek the synergetic effect between the two.The test results show that the wear resistance of Ni-W-P alloy coating(with heat treatment and in oil with nano-ceramic additives) has increased hundreds times than 45 steel as the metal substrate in basic oil,the friction reduction performance is improved.This research breaks through the bottleneck of previous separate research of the above-mentioned two methods,and explores the combination use of the two methods in industrial field.     

电沉积稀土改性陶瓷涂层磨损性能研究

探讨了在电火花加工机床上沉积碳化钛金属陶瓷涂层方法,利用TiC,WC,Mo,N i粉未添加不同比例稀土元素在高压下压制并烧结了试验电极,在45#钢表面沉积了不同稀土含量的TiC陶瓷涂层,并用扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度计、环块式磨损试验机对涂层组成、组织形态进行、硬度及摩擦学性能分别进行了研究,并结合试验结果进行了理论分析。试验结果表明:用电火花放电法可沉积TiC陶瓷涂层,涂层中加入质量分数为0.5%的氧化镧后,涂层的耐磨性能较未加稀土涂层提高了3倍,摩擦因数减少10%,而加入过多的稀土镧氧化物则不利于涂层组织性能及耐磨性能的改善。稀土氧化镧对涂层的组织有改善作用,加入适量的稀土元素使得涂层致密性提高,减少涂层中的缺陷,涂层表面呈多孔结构特性。