用涂层压入仪测定薄膜与基体结合强度的探讨

用新颖的能连续加载、卸载并配有声发射监测的涂层压入仪,对薄膜与基体的结合强度进行了探讨。实验结果表明,膜或膜／基破坏的声发射信号各有特点,可区分压入过程中（含卸载）开裂和剥落及其对应的载荷值。压入法的临界载荷ｐｃ为加载过程中使膜发生初始剥落的外载,用涂层压入仪可精确测量。ｐｃ值对基体硬度和表面粗糙度的变化敏感。故用涂层压入仪可以实现用压入法考察膜／基结合强度。     

用涂层压入仪界面压入测定结合强度的实验研究

用可实行单点连续加载卸载的涂层压入仪，测定热喷涂涂层与基体之间界面开裂的临界载荷ＰＷ，此值可反映结合强度，与现有的压入法比较，用涂层压入仪只需一次压入就可测定Ｐ一次压入就可此方法比粘结拉伸简捷、适合评价高结合强度的涂层。     

压入法测涂层结合强度的研究进展

涂层结合强度是评价涂层质量的重要指标,基于涂层的多样性及复杂性,涂层结合强度的检测方法种类较多.压入法是一种通过施加压入载荷诱导涂层失效以表征涂层结合强度的检测方法,此方法按压入位置的不同可分为侧面压入法、界面压入法及表面压入法;就此3种压入方法进行了综述,介绍了它们的适用范围、检测特点及研究进展,讨论了它们的优势与不足,分析了表面压入法目前存在的研究难点,并提出了相应的解决思路.     

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.     

硬质涂层力学性能可靠测量的两步压入法

正确测量涂层的硬度等力学性能一直是硬质涂层生产和研究中亟待解决的问题。本文提出的采用力学探针对涂层进行两步压入的实验方法可以在未知涂层厚度的条件下通过大载荷逐步加载展示出涂层厚度对载荷选择的要求，从而正确选择加载载荷进行小载荷压入实验。由此方法得到的涂层硬度值和其它力学性能指标具有准确和可靠的特点。     

基于声发射技术的Si-Cr-Ti高温抗氧化涂层弯曲失效机理研究

本研究借助声发射技术对铌基高温抗氧化涂层在常温下的弯曲失效过程进行了研究。利用k均值聚类方法对信号进行了分类, 结合截面扫描电镜观测结果确定高温抗氧化涂层在弯曲载荷下的信号分别对应基体变形、表面垂直裂纹、滑动型界面裂纹和张开型界面裂纹, 通过快速傅里叶变换得到了各类信号的主频分别为100、310、590和450 kHz, 借助小波分析得到了各信号的小波能量系数。涂层弯曲失效过程主要包括四个阶段, 分别为受拉侧表面垂直裂纹萌生的初始损伤阶段、表面垂直裂纹增殖阶段、两侧界面裂纹快速扩展的损伤积累阶段和受压侧涂层明显剥落的宏观剥落阶段。     

高强涂层结合强度的评价--楔形加载法

提出用楔形和载法评价高强度涂层材料与基体的结合强度。该方法利用楔形压头置于有楔形槽的试样中,使楔形压头中心线与涂层基体界面重合,施加静态载荷至试样沿涂层界面开裂,根据试样受力边界条件,给出涂层与基体结合强度的公式。对三种不同涂层的基体材料进行了结合强度试验。结果表明,用楔形加载法可对高强涂层与基体的结合强度进行测试,所得数据分散度与ASTMC633－79标准相同,试验数据不受非随机因素的影响。     

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.     

气相沉积硬质薄膜韧性评价方法——压入法

评价气相沉积硬质薄膜的韧性具有重要的工程意义.本文讨论了压入法评价硬质薄膜韧性的原理、方法和参数选择.压入法的原理是载荷导致裂纹形核、扩展,最终形成压痕周围的径向裂纹,而断裂韧性和裂纹之间存在对应关系.压入法的方法是比较压痕形貌特征,其主要影响因素有基体和载荷.对于韧性基体(如金属),小载荷时硬质薄膜与金属同步塑性变形;大载荷下薄膜破裂,但这种情况可能是结合失效破裂,并不反映薄膜的韧性.对于脆性基体(如硅片),小载荷时裂纹会在Si片中形核,并扩展到薄膜中,形成压痕对角线径向裂纹;大载荷时薄膜会严重破裂.定量评价薄膜韧性时,一般采用硬质薄膜/Si片体系,以0.98~9.8N载荷压入脆性基体,采用纳米压入仪测定薄膜的硬度和弹性模量,采用显微镜测量径向裂纹的长度,利用Lawn公式计算得到断裂韧性值.     

离子束增强沉积界面共混工艺对Cr-N镀层结合强度的影响

采用连续压入法以及球滚接触疲劳法评定不同界面共混工艺所制Ｃｒ－Ｎ镀层膜基结合 强度,并对两种方法试验结果进行分析对比．试验结果表明,在其它参数相同条件下,随着氮离 子轰击能量从１０、２０ｋｅＶ提高到４０ｋｅＶ,动反冲共混界面结合强度则有明显降低的趋势,Ｐ_ｃ 值测量值分别为６５０、７００、３３０Ｎ．当轰击能量为２０、１０ｋｅＶ时,Ｃｒ－Ｎ镀层在△Ｔ_ｒｚ＝４４２ＭＰａ 时,循环疲劳周次达到５．０×１０^６时,镀层未剥落,表现出很高的动态结合强度,而４０ｋｅＶ动反 冲共混界面在△Ｔ_ｒｚ＝４４２ＭＰａ时,循环疲劳周次仅为９．０×１０^５．较低能量（１０、２０ｋｅＶ）氮离子 动态共混界面具有更理想的膜层一基体结合强度．两种方法测试结果具有一致性．当膜层－基 体结合力较高时;压入法评定膜层－基体结合强度更简便、适用．     

用压痕试验法研究CVD金刚石膜的粘附性能

在观察与分析压入过程中CVD金刚石膜开裂方式的基础上,初步探讨了用压痕试验法评定CVD金刚石膜粘附性能的可行性．采用反映膜／基粘附性能的临界开裂或剥落载荷P_er和抗裂性参数dP／dX两指标评定了硬质合金基体表面经不同预处理方法和沉积工艺参数合成的金刚石膜的粘附性能;研究了粘附性能指标与沉积工艺参数（如甲烷浓度、沉积气压、沉积功率）之间的关系．适当的表面预处理、适中的甲烷浓度、较低的沉积气压、较高的沉积功率均有利于改善金刚石膜的粘附性能．     

Finite element analysis of interface delamination and buckling in thin film systems by wedge indentation

A finite element method is used to study the interface delamination and buckling of thin film systems subject to microwedge indentation. In the formulation, the interface adjoining the thin film and substrate is assumed to be the only site where cracking may occur. Both the thin film and the substrate are taken to be ductile materials with finite deformation. A traction-separation law, with two major parameters: interface strength and interface energy, is introduced to simulate the adhesive and failure behaviors of the interface between the film and the substrate. The effects of the interface adhesive properties and the thickness of the thin film on the onset and growth of interface delamination and the film buckling are investigated.     

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。     

A numerical study of contact damage and stress phenomena in curved porcelain/glass-filled polymer bilayers

Finite Element Analysis is used to examine contact damage induced by Hertzian indentation of a porcelain coating on a glass-filled polymeric substrate. Different forms of cracking in the porcelain coating are studied –“Hertzian” cone cracks close to the indenter, more distant “outer” cone cracks, and “radial” cracking at the coating/substrate interface. The effects of porcelain coating thickness and radius of curvature on the critical stresses for initiation of these cracks are examined. The predicted critical load curves suggest that for systems with compliant substrates (relative to the coating) with a given radius of curvature, there is an optimum porcelain coating thickness that maximises the critical load for cone cracking. Conversely, for a given coating thickness, the effects of curvature vary significantly – for thinner coatings, where outer cone cracks are dominant, highly convex surfaces are more resistant to cracking, whereas for thicker coatings, which are more prone to Hertzian cone cracking, concave surfaces produce a higher predicted critical load. Curvature is observed to have little effect on the critical load for the formation of radial cracks, which remains the dominant mode of failure in cases of thin coatings on compliant substrates.     

Mechanical and thermal properties of physical vapour deposited alumina films Part II Elastic, plastic, fracture, and adhesive behaviour

Two mechanical characterization techniques were used to deduce the elastic, plastic, fracture, and adhesive properties of non-reactive physical vapour deposited alumina films of varying thickness on Al₂O₃-TiC substrates deposited at two different substrate biases. Depth-sensing indentation at both nano- and macroscopic load scales was used to determine the elastic and plastic properties of the films. Gravity-loaded Vickers indentation was performed to examine the fracture properties of the film and of the interface. Novel fracture mechanics models were developed to describe indentation-induced film fracture by channel cracks and indentation-induced interface delamination. The former model was used to determine the film toughness and the latter model was used to deduce the interfacial fracture resistance of the films and correctly predicted the effect of changing film thickness. Both models described the measured crack lengths with indentation load well and were used to identify the transition from radial and lateral cracking to channel and interfacial cracking.     

Failure assessment of a hard brittle coating on a ductile substrate subjected to cyclic contact loading

Hard brittle films and coatings are often employed as a protective coating for metallic ductile substrates. In use, such coatings are generally subjected to cyclic/repeated contact loading and sliding over long periods of time. This study investigated the monotonic and cyclic contact fracture mechanism of hard coatings on ductile substrates (an electroplated Ni–P coating on a stainless steel substrate, SUS304) in order to evaluate their mechanical durability. In the experiment, both monotonic and cyclic indentation tests using a ball indenter with large contact force were performed. The fracture nucleation process was identified using the acoustic emission method. For monotonic contact loading (single indentation), coating cracks are produced by the excessive plastic deformation of the substrate, itself caused by contact loading, which makes the bending curvature of a coating a critical moment. Subsequently, cyclic contact loading (cyclic indentation) was applied to the coating in order to investigate the cycle number of film cracking. It was found that the critical contact force for coating fracture decreases, compared with that of monotonic loading. This critical force is dependent on the number of loading cycles. This may be due to the fact that cyclic contact loading encourages large plastic deformation of the SUS304 substrate owing to cyclic plasticity. Therefore, the cyclic plastic deformation behavior of the substrate was investigated using cyclic microindentation tests and the finite element method. In the computation, the Chaboche model was employed to compute the cyclic plastic deformation of the substrate, since it simulates cyclic plasticity. We clarified the cyclic contact fracture mechanism of electroplated Ni–P coating on an SUS304 substrate. Based on this, we finally predicted the coating lifetime (i.e., mechanical durability) under cyclic contact loading. Therefore, the present study is useful for obtaining information about film/coating fracture properties under both monotonic and cyclic contact loadings.     

Modelling the limits of coating toughness in brittle coated systems

As the accuracy and applicability of existing indentation models to assess coating toughness can be affected by many factors (such as fracture mechanisms, crack type, coating thickness, cracking size etc), it is uncertain to what extent the values obtained are quantitatively correct. Therefore, an estimation of the limits of coating toughness is very useful. In this paper, a limits model is proposed to assess coating toughness based on numerical and phenomenological analysis. This approach provides universal expressions for the lower and upper bounds of fracture dissipated energy for indentation performed under load control and displacement control. It has shown that the lower bound determined in this study is also a good estimation of the coating toughness.     

Determining buckling strain energy release rate through indentation-induced delamination

An oscillating indentation load was applied to delaminate a diamond-like-carbon film from a silicon substrate. After delamination occurred, a two-stage behavior was exhibited in the load-depth results; then, a three-stage behavior was exhibited after buckling occurred due to a long enough delamination length. After removing the indentation load, the debonding film was single-buckled and suspended over the substrate; thus, the delamination length was obtained via the residual profile. Through analysis of the deflection of the buckled film, the buckling strain energy release rate was evaluated.     

Role of mass accumulation and viscoelastic film properties for the response of acoustic-wave-based chemical sensors

The sensitivity of acoustic-wave microsensors coated with a viscoelastic film to mass changes and film modulus (changes) is examined. The study analyzes the acoustic load at the interface between the acoustic device and the coating. The acoustic load carries information about surface mass and film modulus; its determination has no restrictions in film thickness. Two regimes of film behavior can be distinguished: the gravimetric regime, where the sensor response is mainly mass sensitive, and the nongravimetric regime, where viscoelasticity gains influence on the sensor response. We develop a method, which allows the assignment of the sensor signal to a gravimetric or a nongravimetric response. The critical value can be determined from oscillator measurements. The related limits for the coating thickness are not the same for the coating procedure and mass accumulation during chemical sensing. As an example, we present results from a 10 MHz quartz crystal resonator.     

平头压头下基体对压痕规律的影响研究

本文通过对软薄膜/硬基体两相材料体系的平头压痕弹塑性模拟.重点研究了平压头压入过程中,不同屈服强度比(软薄膜屈服强度与硬基体屈服强度之比)以及不同压头尺寸下硬基体对压痕规律的影响.研究发现硬基体对压痕规律的影响与屈服强度比近似满足线性关系,且这种线性关系不随压头尺寸的改变而改变,相同压头半径下,屈服强度比越大,影响就越明显;相同屈服强度比下,压头半径越大,影响就越小.研究还发现压头压入过程中,材料的堆积对压入深度没有影响.