残余应力对压头诱导的硬质薄膜/韧性基底材料体系界面分层机制的影响

硬质薄膜在工程应用中经常承受高载荷作用。在接触载荷下,薄膜/基底体系通常产生剪切分层破坏和法向分层破坏,并直接影响材料的可靠性。硬质薄膜中较大的残余应力对界面分层破坏影响不容忽视。该文基于内聚力模型,采用有限元方法模拟残余应力对压头诱导的硬质薄膜/韧性基底界面分层破坏的影响规律;给出在不同残余应力下薄膜/基底界面分层破坏时的临界压入深度以及临界载荷;获得考虑残余应力时硬质薄膜/韧性基底界面分层破坏失效图,进而对薄膜材料的工程应用和采用压痕法测量界面结合性能提供指导。     

金刚石涂层基体间结合力的测定

结合力是制约金刚石涂层工具大规模应用的关键因素之一.针对热丝化学气相沉积制备的金刚石薄膜的膜基结合力进行划痕实验,运用划痕仪所测的声发射数据、摩擦力数据及光学、电子扫描划痕形貌来综合评定膜基结合力.评定结果表明:单一的声发射图谱或摩擦力曲线不能准确判定膜基结合力的表征值临界载荷,声发射图谱、摩擦力曲线与划痕形貌综合评定临界载荷结果才可信.     

划痕法综合评定膜基结合力

用划痕实验探索了综合表征膜基结合力的方法.在瑞士CSM仪器的微划痕测试仪(Micro-Scratch Tester,MST划痕仪)对真空多弧离子镀设备制备的WC-Co/TiN膜基结合力进行划痕实验,系统地介绍了如何利用MST划痕仪所测的声发射数据、摩擦力数据及光学、电子扫描划痕形貌来综合评定膜基结合力,并用WS-92划痕仪对评定结果进行验证.评定结果表明,单一的声发射图谱或摩擦力曲线不能准确判定膜基结合力的表征值临界载荷,声发射图谱、摩擦力曲线与划痕形貌综合评定临界载荷结果才可信.WS-92划痕仪测量的结果验证了MST划痕仪评定结果的准确性.     

TiN/TiCrN/TiCrAlN复合薄膜膜基结合力测定与分析

使用划痕仪对多弧离子镀制备的TiN/TiCrN/TiCrAlN复合薄膜进行了划痕实验,结合金相显微镜观察分析划痕表面形貌,综合判定了该复合薄膜的膜基结合力。结果表明,该薄膜的失效形式为周边剥落;单一的声信号曲线不能准确判定薄膜失效的临界载荷,需要声信号曲线与划痕形貌的综合判定。     

用划痕试验法测定薄膜附着性过程中薄膜破裂形态的研究

本文通过对表征TiN、TiC薄膜与基体间附着力的划痕试验结果的深入分析发现,划痕试验中,压头在簿膜上的滑动特征以及标志此特征的作用于压头上的垂直力(载荷)与水平力(摩擦力)构成的曲线不但与薄膜与基体间的结合力有关,而且与薄膜的表面形态、膜厚以及薄膜的韧性等因素有关。薄膜破裂时,压头在薄膜上的滑动特征发生突然变化,伴随摩擦系数变化及摩擦力的剧烈变化。这些变化可做为判定薄膜临界载荷的依据,用扫描电子显微镜(SEM)和电子探针显微分析仪(EPMA)对不同基体的TiN、TiC薄膜的破裂形态进行了系统的研究,探讨了影响薄膜破裂形态的主要因素及薄膜破裂形态与正确判定临界载荷间的关系。     

过渡层对TiN涂层结合力的影响

研究了不同过渡层TiN涂层结合力的影响,用划痕法测定了临界载荷Lc,扫描电镜观察了划痕形貌。结果表明,4种TiN复合涂层的结合力和硬度均明显高于TiN单层,其中Ni－W过渡层地结合力提高幅度最大,并对TiN涂层起到有力的支撑作用。以M2为基体的TiN复合涂层的临界载荷均高于硬度较低的、以3Cr2W8V钢为基体的TiN复合涂层的临界载荷。     

GCr15轴承钢表面PⅢD处理膜层膜基结合力的研究

采用等离子体浸没离子注入沉积(PIIID)技术在GCr15轴承钢表面形成TiN薄膜,并采用划痕法对不同参数条件下膜层的膜基结合力进行了测量.结果发现:适当的氩离子溅射清洗和加入合适的过渡层可以提高膜基结合力,而且膜基结合力也会随着注入电压和注入量与沉积量比例的变化而改变.     

磁控溅射法制备铁氧体薄膜的界面结合强度研究

利用磁控溅射法在单硅晶基底和玻璃基底上沉积铁氧体薄膜,采用AFM观察薄膜的微观形貌,采用划痕法测试薄膜的界面结合强度,测试结果表明:由于两种不同材质上沉积的薄膜粗糙度缘故,硅晶/铁氧体薄膜的临界载荷为19.7N,其划痕形貌为裂纹状扩展,玻璃/铁氧体薄膜的临界载荷为5.3N,其划痕形貌为剥落状。     

线接触作用下超薄膜-基底界面力学分析

高副接触的摩擦部件中广泛使用1 μm左右的超薄膜,其界面失效对部件的工作寿命具有重要影响。该文针对轴承钢基底表面1 μm厚度的硬质和软质超薄膜所构成的膜基系统,建立了线接触载荷作用下的界面力学分析模型。采用复变函数镜像法求解了单元点力的格林函数解,并积分获得了界面应力的分布状态。利用匀质模型完成了退化对比验证,以DLC和MoS₂两种硬软固体薄膜的线接触为例进行了计算和分析。该方法可用于机械部件表面沉积超薄膜的膜基界面分析与设计。     

合理使用划痕法及显微法测定TiN薄膜与基体结合力

采用反应磁控溅射的方法在TC4钛合金基板上制备了TiN薄膜,利用划痕法测试了TiN薄膜与基体之间的结合力,并结合薄膜硬度与显微法判断的临界载荷进行了对比分析。结果表明:单纯依靠划痕法判断临界载荷较为局限,结合显微法同时考虑硬度等力学性能共同判断临界载荷,是更为科学合理的办法。     

声发射监听划痕法评价膜层结合情况的有效性

本文介绍声发射技术在判断划痕临界载荷以推定膜层与基材结合情况的研究结果。实验的试样是玻璃基材真空蒸镀铝膜、软钢上电镀镍层以及不同硬度的钢样上离子镀超硬氮化钛膜层。在脆性硬质基材上无论镀软膜或硬膜,划痕试验中一旦监听到声发射信号即表明基材与膜层结合失效,此时的划痕载荷即为临界载荷。塑性基材镀软膜层直到划痕到基材也无声发射信号出现。超硬膜层与钢基材的划痕试验中,声发射信号出现时载荷往往低于临界载荷。两者的差值决定于超硬膜的厚度和膜层与基材的硬度差。     

Micro-scratch analysis and mechanical properties of plasma-deposited silicon-based coatings on polymer substrates

Advanced optical applications require multifunctional coatings with specific mechanical properties, such as resistance to damage and good adhesion to different types of substrates, including polymers. In the present study we deposited amorphous hydrogenated silicon nitride (SiN_1.3) and oxide (SiO₂) films on polycarbonate and on silicon substrates by plasma enhanced chemical vapor deposition (PECVD), using a dual-mode microwave/radio frequency plasma system. The film adhesion was determined by the micro-scratch test. Depth-sensing indentation and substrate curvature measurements were used to evaluate the microhardness. Young's modulus and residual stresses of the films. The adhesion strength, represented by the critical load, L_c, when the film starts to delaminate, was determined as a function of the substrate material and the energy of bombarding ions. A direct correlation between the L_c values and the mechanical properties of the films was found. The formation of different crack patterns in the coatings during the scratch procedure is explained in terms of stress release mechanism depending on the mechanical properties of the film, the substrate and the interface region. In addition, different models applicable to the evaluation of the work of adhesion in the case of hard coatings on soft substrates are critically reviewed.     

Effect of substrate temperature on the adhesion properties of magnetron sputtered nano-composite Si-C-N hard thin films

The adhesion and film failure studies on nano-composite SiCN thin films on silicon, glass and steel have been carried out. It was observed that both coating as well as the substrate has an influence on the adhesion of film. The films on hard substrate Si failed adhesively whereas on softer substrate, steel, cohesive failure was observed. The measured critical load was around 18 N and 24 N for SiCN film on silicon and steel substrate respectively. A decrease in critical load and interface toughness with the increase of substrate temperature during deposition for glass and steel substrate was observed.     

Scratch adhesion testing of hard coatings

The scratch test for adhesion is reviewed as the only method currently available for testing thin, hard and well-adhering coatings such as TiC on steel or cemented carbide substrates. The critical load, mode of coating removal and acoustic signals are discussed. It is found that the combination of acoustic signal with microscopic observations can indicate whether failure occurs following a cohesive or an adhesive mode. The critical loads increase with increasing coating thickness in a manner which is a characteristic of the coating-substrate combination being studied. Critical loads are higher for harder tougher substrate materials; they also appear to depend on the elastic modulus and the coefficient of friction of the coating itself.     

Hard coatings on light-metal components under mechanical surface loading

In this work the behaviour of hard coated light-metal components was investigated when they are mechanically loaded. Three lightmetal alloys, Ti-6Al-4V, AlSi7Mg and AlMgSi0.5 and 100Cr6 steel (as a reference material) were coated by two different physical vapour deposition processes: radio frequency magnetron sputtering and electron beam evaporation. The coating materials utilised were CrN and TiN. Standard test methods with different loading conditions were used to evaluate the substrate/coating-combinations: the hardness test (applying a static normal load), the scratch test (applying a combination of a static normal and a static tangential force) and the impact test (applying a dynamic normal load). It was observed that the load support of coated materials depends on the loading conditions. The coated aluminium alloys showed poor load support under all loading test conditions but produced a higher surface hardness than uncoated steel. Coated Ti-6Al-4V showed very good load support properties, similar to coated steel. All coated light-metal substrates demonstrated significant improvement in load support behaviour with an increase in coating thickness. The results of the scratch test, which is commonly used to asses adhesion properties of thin coatings, showed an immediate indenter-breakthrough on the aluminium alloy substrates, but causing no coating delamination. Due to this behaviour, the scratch test is not suitable to evaluate adhesion properties on coated soft light-metals. Yet the impact test allowed assessment of coating delamination on the aluminium alloys, proving its usefulness for adhesion measurement even on soft substrates. The study indicates that substitution of steel with coated lightmetal alloys is a viable proposition for certain applications.     

Spallation failure maps from scratch testing

The use of the scratch test to assess the adhesion of a range of hard coatings is well established. The technique can provide a semi-quantitative measure of adhesion provided that a well-defined adhesion-related failure mode is used as a basis for the assessment. In this study the testing has been extended to thermally grown oxides and it has been determined that both buckle and wedging failure modes can be identified in the scratch test depending on the thickness of the oxide and the mechanical properties of the substrate. The critical normal load at which these failure modes are first observed as a function of thickness can be used to determine those compressive and shear loading regimes where the oxide scale is stable with respect to spallation. This approach can also be applied to hard coatings, such as TiN deposited by physical vapour deposition. The experimental observations are discussed in light of theoretical models for scale spallation.     

Scratch adhesion test of reactively sputtered TiN coatings on a soft substrate

Reactively sputtered TiN coatings on the relatively soft substrate, Crofer 1700 (Vickers' hardness about 176 HV), were subjected to a scratch test for adhesion. The critical load of the coating/substrate combination is defined as the load at the onset of coating failure as cracking or loss of the coating that causes an increase in acoustic emission. For example, at the critical load of a thicker coating (approximately 1.5 μm), not only cracking but also loss of the coating were observed with an increase in acoustic emission. However, at the critical loads of thinner coatings (1.2 μm or less), coating loss was not observed in spite of an increase in the emission but coating cracking did occur. A failure model is suggested for the given coating plus soft substrate system. Using this model, the maximum observed in a typical acoustic emission curve is explained.     

高速钢上氮化碳薄膜附着力及其影响因素的研究

氮化碳(CNx)薄膜具有优异的力学性能和摩擦学性能,很适合用作耐磨保护涂层及固体润滑剂.采用磁控溅射法在高速钢(HSS)基片上制备了氮化碳薄膜,并以划痕法对其附着力进行了研究.结果表明:有TiN中间层的CNx复合薄膜比无TiN中间层的附着性能有较大的提高.CNx/TiN复合薄膜附着性能较好的主要原因是:对基片严格的清洁处理,采用磁控溅射法对基片施加了合适的负偏压,沉积了合适的中间过渡层;工艺参数合理.     

WC-Co硬质合金基体上高附着力金刚石薄膜的制备

采用微波等离子体化学气相沉积(CVD)法在WC-Co硬质合金基体上制备金刚石膜, 研究了TiN_x中间层的引入对金刚石薄膜质量及其附着性能的影响. 结果表明, 在酸浸蚀脱钴处理的基础上, 通过预沉积氮含量呈梯度变化的TiN_x中间过渡层, 可在硬质合金基体上制备出高质量的金刚石薄膜; 压痕法测试其临界载荷达1000N.