离子束辅助沉积（Ti,Al）N梯度薄膜的结合强度

本文采用离子束辅助沉积技术，制备了不同成分梯度的一系列（Ｔｉ１－ｘＡｌｘ）Ｎ膜（其中ｘ＝０．１６～０．４４），并利用刮剥式结合强度测量方法，对薄膜成分对结合强度、内应力、硬度等的影响进行了研究。研究工作发现，刮剥法测得的结合强度，在ｘ＝～０．３１处取得最大结合强度值后，随薄膜成分梯度的增大而下降，但在重要的４０％～５０％Ａｌ区域内，梯度（Ｔｉ，Ａｌ）Ｎ膜的结合强度、硬度以及内应力却都维持在一个较为稳定的水平，较少受薄膜成分等的影响。梯度（（Ｔｉ，Ａｌ）Ｎ膜的结合强度主要受膜中残余应力的影响。     

新型界面结合强度检测技术理论及实验研究

膜/基界面结合强度的测量与评价已成为硬质薄膜技术发展与应用的关键问题.提出了1种新的测量方法———激光冲击检测技术,分析了在脉冲激光作用下,薄膜脱落的机理与数学模型.以测定TiN薄膜界面结合强度为例,用650～1000 mJ的脉冲激光对膜层进行加载,并采用体式显微镜和扫描电镜对薄膜的脱落情况进行表面观察,根据反射信号检...     

激光划痕界面失效进程研究

1、引言 薄膜技术是材料提高表面性能的重要手段之一.膜基界面结合性能是影响表面薄膜质量的首要指标,其在很大程度上决定了薄膜应用的可靠性和和使用寿命.界面结合强度有工程结合强度(practical adhesion)和本征结合强度(foudamental or intrinsic adhension)两种形式,本征结合强度是相接触的两材料界面的所有分子间作用力的总和,是使处于测试条件下的膜-基系统的最薄弱界面的化学结合产生破坏所需要的能量;工程结合强度是指将薄膜从基体上去除所需要的力或功,也可表示为在特定应力状态下使薄膜剥离所需要的时间[1,2].     

基片弯曲法分析Ag/Fe多层膜退火过程中界面应力的变化

有关薄膜应力的一般测量方法存在精度不高和不能实时测量的缺点。多层薄膜材料是在非平衡条件下制备的性能优异并包含高密度界面的新型亚稳定材料，由于其结构的差异，一般测量薄膜应力的方法如X射线衍射法、拉曼光谱法等失去作用。阐述了基片弯曲法测量薄膜应力的原理，设计了用光杠杆法测量试样曲率的装置，并实时测量了Si基Ag／Fe多层膜在退火过程中表面弯曲曲率的变化。同时开发了软件处理系统，并计算和分析了Ag／Fe多层膜退火过程中膜-基界面的应力变化。研究表明，经过退火处理的薄膜应力有极大的增加，其中升温过程发生了再结晶，使薄膜应力降低，而降温过程则使应力不断增加。     

磁控溅射铜膜与基底结合强度的分析研究

根据磁控溅射金属铜膜在超声清洗中从硅基底上发生剥落的现象,分析了样品在声场中的运动和受力状态,发现样品会发生受迫振动,拉-拉周期应力引起膜基界面的失效是薄膜脱落的主要原因,而空化作用是次要原因。通过建立的力学模型,计算了膜基结合强度。与划痕法等所测得的膜基结合强度值的比较,计算值与测量值在数量级和与溅射参数变化趋势上有很好的吻合。此评价方法可以应用于溅射铜膜/多晶金刚石的膜基体系上,并研究了超声参数、基底表面形貌、基底成份等因素对膜基结合强度的影响。     

基于弹塑性滚动接触疲劳法评价硬质薄膜结合强度

滚动接触疲劳法表征结合强度的剪切应力幅是一个对界面因素敏感,而对非界面因素不敏感的力学参量,能真实反映膜基结合状态,是较为合理的动态结合强度评价方法。但由于应力计算的模型采用弹性力学方法,对膜基结合强度较高而厚度很小的薄膜,往往加大载荷也较难使膜基界面发生分离。本文采用小直径、高弹性模量Al_2O_3球的滚动接触疲劳方式,对高结合强度的硬质薄膜进行评价,并采用有限元方法计算弹塑性变形条件下的应力分布,切应力幅的计算结果具有合理性。改进后的滚动接触疲劳法允许基体发生弹塑性变形,界面切应力大幅度提高,能够在相对较少周次下造成薄膜剥落,失效部位发生于界面,因而更适合于评价结合强度较高的硬质薄膜。     

物理气相沉积薄膜的界面与附着力

近十多年来，气相沉积技术发展十分迅速，无论在理论研究还是应用研究上都取得了丰硕的成果，尤其在PVCD薄膜的附着务方面.研究十分，本文根据有限的资料，初步归纳出：D PVD过程中，膜／基附着力与基体表面活性密切相关，薄膜与基体之间也可以化学吸附形式结合，形成界面化合物，也可借助离子的轰击作用形成结合良好的扩散过渡层，膜／基界面之间不匹配将使附着力下降，可通过设置过渡层（梯度层）的方式加以解决。     

第十七讲 薄膜与表面技术基础

附着力的测量方法可分为粘结法和非粘结法两种:前者是利用粘结剂把一施力物体贴在膜层表面,在此物体上施加力使膜层剥离,大多用于较厚的膜层;后者大多用于薄膜层,是直接在薄膜上施加力使薄膜剥离.用粘结法容易测量附着力,但当测定的附着力比粘结力或粘接剂的强度还大时,就不能采用这种方法了.     

动态结合强度试验机的研制及应用

介绍了滚动接触疲劳法测定硬质薄膜膜基界面疲劳强度的方法，以及动态结合强度试验机的原理、结构及其应用。试验结果表明，用该试验机测得的膜基界面疲劳强度能定量地反映膜基界面之间的结合强度，且该方法对膜的成分和基体表面状态等界面因素敏感，而对基体硬度和膜层厚度等非界面因素不敏感。     

真空技术及应用系列讲座 第十七 讲薄膜与表面技术基础

(上接2012年第1期第88页)附着力的测量方法可分为粘结法和非粘结法两种:前者是利用粘结剂把一施力物体贴在膜层表面,在此物体上施加力使膜层剥离,大多用于较厚的膜层;后者大多用于薄膜层,是直接在薄膜上施加力使薄膜剥离。用粘结法容易测量附着力,但当测定的附着力比粘结力或粘接剂的强度还大时,就不能采用这种方法了。     

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。     

Adhesive and bending failure of thermal sprayed hydroxyapatite coatings: Effect of nanostructures at interface and crack propagation phenomenon during bending

Hydroxyapatite (HA) coatings have shown promising effects on rapid bone remodeling and suitable functional life in orthopedic and dental applications. However, the major problem encountered by the HA-coated implants is the failure of the coating due to its insufficient mechanical properties. The present study investigated the influence of the microstructure near to the coating/substrate interface on the adhesion of the coatings. In addition, the crack propagation behavior within the coatings was studied through 4-point bend test. Results showed that nanostructures (30-110 nm) within the HA coatings were achieved by high velocity oxy-fuel (HVOF) spraying. Comparison among HVOF HA coatings, which were deposited using different starting feedstock, suggests detrimental effect of the perpendicular-to-substrate nano-cuboids on adhesion of the coatings. The presence of the grains with hexagonal shape (<250 nm in length and <50 nm in diameter) triggered a deteriorated adhesion. Granular nanosized grains at the interface give rise to enhanced adhesion through improved mechanical interlocking. Formation mechanism of the nanosized grains was discussed in this paper. Furthermore, the 4-point bend test revealed consistent crack propagation path that the cracks actually grow within the coating with a direction parallel to the interface, and approximately several to 20 microns thick coatings were remained on the substrate. The critical strain energy release rate exhibited a value of ∼1.15 kJm⁻². During the crack propagation, kinking and trapping of the bending cracks were decided by the flaws within the coating, which were mainly located at splats’ interface. The interface between the first layer (with one splat thickness) and the second is believed to be the weakest zone in the nanostructured coating.     

Interfacial study of magnesium-containing fluoridated hydroxyapatite coatings

Magnesium-containing fluoridated hydroxyapatite (Mg_xFHA) coatings have been developed to improve the biological performances of fluoridated hydroxyapatite (FHA) coatings. The coatings are deposited on Ti6Al4V substrates via a sol-gel process. The interface between the coating and substrate is characterized by scanning electron microscopy, glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy for coating thickness, elemental distribution and chemical states. Pull-off test is used to evaluate the adhesion strength. The results show that the interdiffusion of elements happens at the coating/substrate interface. The incorporation of Mg ions into FHA coatings enhances the pull-off adhesion strength between the coating and the substrate, but no significant difference is observed with different Mg concentrations.     

Mechanical properties and adhesion strength of TiN and Al coatings on HSS, steel, aluminium and copper characterized by four testing Methods

TiN and Al coatings on substrates of high-speed steel, steel, aluminium and copper have been used to study mechanical properties of coating systems, especially the adhesion of the coating. The quantities measured are internal stress of the coating, determined by X-ray diffraction, the critical load of the scratch test, the microhardness obtained by the indenter technique, and the interface fracture energy, determined by a three-point bend test developed recently by the authors. The fracture energy, G_c, is a measure for the adhesion strength of a coating system. The effect of bias voltage, sputter cleaning and contamination of the substrates on the adhesion strength and other mechanical properties are investigated with the four methods mentioned. Each of the testing methods reveal only specific aspects of the behaviour of the coating systems. The data obtained depend on bulk properties of the film and the substrate material and on properties of the interface. Variation of the bias voltage can change them in quite different ways. In addition, the inter-relations between the adhesion strength of the coating and the failure behaviour of the three-point bend test samples are discussed.     

Study of adhesion of PROTAL® copper coating of Al 2017 using the laser shock adhesion test (LASAT)

Surface preparation of substrates is a major stage in thermal spraying as it greatly influences coating adhesion. Standard grit-blasting creates roughness but also often leaves grit inclusions at the substrate surface, which are detrimental for coating quality. In contrast, the use of smooth substrates involves improvements in metallurgical adhesion.This work deals with the use of substrate pre-heating and of the PROTAL® process (PROjection Thermique Assistée par Laser) to promote metallurgical adhesion. PROTAL is based on substrate laser treatment prior to spraying to achieve an oxide-free interface and, under specific conditions, which modifies the substrate morphology. A metallurgically reactive system (i.e., copper sprayed onto Al 2017) was selected to be suitable for controlling metallurgical features at the coating-substrate interface (mainly pores, intermetallic phases and pre-existing cracks). These were shown to depend on substrate roughness and on the substrate temperature during the first spraying pass.LAser shock adhesion test, namely LASAT, was developed to enable morphological and metallurgical features of as-sprayed interfaces to be studied separately. The existence of a critical roughness for anchoring (CRA) and of an adhesion transition temperature (ATT) could be assumed. As for metallurgical properties, interface intermetallics and pre-existing cracks were shown to be detrimental for adhesion. Moreover, LASATesting succeeded in showing that adhesion of PROTAL coatings is better than that of APS-only coatings.     

Quantitative evaluation of the adhesion of metallic coatings using cylindrical substrate

This paper introduces an effective interfacial fracture toughness test based on interface fracture mechanics theory. This testing method uses a circumferentially notched tensile (CNT) specimen, which is ideally suited for determining the interfacial fracture resistance of coatings. Unlike other interfacial fracture tests, this test is simple to prepare, requires minimum test setup and is easy to model. An interfacial pre-crack was generated between a nickel coating and mild steel cylindrical substrate to evaluate adhesion strength. In situ acoustic and SEM analyses were used to determine the crack initiation or the critical load of failure. The critical energy release rate, critical stress intensity factors and phase angle were determined using the J integral which was determined by applying the critical load to the finite element model. A detailed finite element analysis was carried out to study the effect of different interface pre-crack positions and mode mixity on energy release rate for different notch angles and elastic modulus ratios. The cracking resistance of the interface was characterised by the notch angle of CNT specimens. The analysis showed an increase in interfacial fracture toughness as phase angle increases and was significant when the phase angle was large. The combined results of computational and experimental analysis showed that any defect or stress concentration at the interface could significantly weaken the adhesion of coating.     

CVD nanocrystalline diamond coatings on Ti alloy: A synchrotron-assisted interfacial investigation

Diamond coating on Ti-6Al-4V alloy was carried out using microwave plasma enhanced CVD with a super high CH₄ concentration, and at a moderate deposition temperature close to 500 °C. The nucleation, growth, adhesion behaviors of the diamond coating and the interfacial structures were investigated using Raman, XRD, SEM/TEM, synchrotron radiation and indentation test. Nanocrystalline diamond coatings have been produced and the nucleation density, nucleation rate and adhesion strength of diamond coatings on Ti alloy substrate are significantly enhanced. An intermediate layer of TiC is formed between the diamond coating and the alloy substrate, while diamond coating debonding occurs both at the diamond-TiC interface and TiC-substrate interface. The simultaneous hydrogenation and carburization also cause complex micro-structural and microhardness changes on the alloy substrates. The low deposition temperature and extremely high methane concentration demonstrate beneficial to enhance coating adhesion strength and reduce substrate damage.     

磁控溅射工艺参数对Cu,Al薄膜与Gd基底附着性的影响

为了探讨Gd表面溅射保护膜的附着性能,利用直流磁控溅射技术在Gd基体上分别镀Cu和Al膜.用扫描电镜(SEM)和能谱仪对薄膜进行表征,用引拉法测定了薄膜的附着强度.结果表明:A1膜表面质量好,Al/Gd界面结合好,附着强度高,在优化工艺参数条件下薄膜附着强度可达到27.60 MPa;Cu膜表面质量较差,Cu/Gd界面结合差,附着强度低,在优化工艺参数条件下薄膜附着强度最高仅为3.02 MPa.     

Adhesion and hardness of ion-plated TiC and TiN coatings

The microhardness and adhesion of TiC coatings on steel and cemented carbide are studied. A comparison with TiN coatings is also made. It is found that the minimum coating thickness in which a reliable microhardness measurement can be made is described satisfactorily by existing standards; departures can be expected if the coating is strongly textured. The critical load for the removal of the coating by the scratch test depends on both the coating and the substrate and is thought to reflect their mechanical properties. It appears that marked variations in the strength and nature of adhesion on cemented carbides can occur.