Structure,hardness and tribological properties of nanolayered TiN/TaN multilayer coatings

TiN/TaN coatings, consisting of alternating nanoscaled TiN and TaN layers, were deposited using magnetron sputtering technology. The structure, hardness, tribological properties and wear mechanism were assessed using X-ray diffraction, microhardness, ball-on-disc testing and a 3-D surface profiler, respectively. The results showed that the TiN/TaN coatings exhibited a good modulation period and a sharp interface between TiN and TaN layers. In mutilayered TiN/TaN coatings, the TiN layers had a cubic structure, but a hexagonal structure emerged among the TaN layers besides the cubic structure as the modulation period went beyond 8.5 nm. The microhardness was affected by the modulation period and a maximum hardness value of 31.5 GPa appeared at a modulation period of 8.5 nm. The coefficient of friction was high and the wear resistance was improved for TiN/TaN coatings compared with a homogenous TiN coating, the wear mechanism exhibited predominantly ploughing, material transfer and local spallation.     

Cr层厚度对Pd/Cr/Co多层膜光学性质的影响

本文利用磁控溅射的方法生长不同Cr插层厚度的Pd/Cr/Co多层膜,并利用椭偏仪对多层膜的光学常数进行测量.得到了入射光波长在250nm-850nm范围内多层膜的折射率、反射率、吸收系数以及复介电常数的曲线,在此数据的基础上分析了Cr插层厚度对多层膜光学参数的影响.     

The effect of magnetic layer thickness on magnetic properties of Fe/Cu multilayer nanowires

Fe/Cu multilayer nanowires were ac-pulse electrodeposited into the anodic aluminum oxide templates prepared by a two-step mild anodization technique. Transmission electron microscopy images showed the distinct layers with a relatively high contrast. A highly pure layer (∼99%) was achieved by tuning the proper ions ratio and optimizing the off-time between pulses of each layer in the single electrodeposition bath. Fe/Cu multilayer nanowires with 38 nm diameter were obtained. The effect of reducing the Fe layer thickness on the magnetic properties of Fe/Cu multilayer nanowires was investigated. It was seen that reducing the Fe layer thickness, thereby variation of rode- to disc-like multilayer nanowires, caused to rotate the magnetic easy axis from parallel to perpendicular to the wires axis.     

Structure, hardness and thermal stability of nanolayered TiN/CrN multilayer coatings

Nanolayered TiN/CrN multilayer coatings were deposited on silicon substrates using a reactive DC magnetron sputtering process at various modulation wavelengths (Λ), substrate biases (V_B) and substrate temperatures (T_S). X-ray diffraction (XRD), nanoindentation and atomic force microscopy (AFM) were used to characterize the coatings. The XRD confirmed the formation of superlattice structure at low modulation wavelengths. The maximum hardness of the TiN/CrN multilayers was 3800 kg/mm² at Λ=80  Å, V_B=−150 V and T_S=400°C. Thermal stability of TiN, CrN and TiN/CrN multilayer coatings was studied by heating the coatings in air in the temperature range (T_A) of 400-800°C. The XRD data revealed that TiN/CrN multilayers retained superlattice structure even up to 700°C and oxides were detected only after T_A?750°C, whereas for single layer TiN and CrN coatings oxides were detected even at 550°C and 600°C, respectively. Nanoindentation measurements showed that TiN/CrN multilayers retained a hardness of 2800 kg/mm² upon annealing at 700°C, and this decrease in the hardness was attributed to interdiffusion at the interfaces.     

Influence of multi-interfacial structure on mechanical and tribological properties of TiSiN/Ag multilayer coatings

The TiSiN/Ag multilayer coatings with bilayer periods of ~50, 65, 80, 115, 150, and 410 nm have been deposited on Ti6Al4 V alloy by arc ion plating. In order to improve the adhesion of the TiSiN/Ag multilayer coatings, TiN buffer layer was first deposited on titanium alloy. The multi-interfacial TiSiN/Ag layers possess alternating TiSiN and Ag layers. The TiSiN layers display a typical nanocrystalline/amorphous microstructure, with nanocrystalline TiN and amorphous Si₃N₄. TiN nanocrystallites embed in amorphous Si₃N₄ matrix exhibiting a fine-grained crystalline structure. The Ag layers exhibit ductile nanocrystalline metallic silver. The coatings appear to be a strong TiN (200)-preferred orientation for fiber texture growth. Moreover, the grain size of TiN decreases with the decrease of the bilayer periods. Evidence concluded from transmission electron microscopy revealed that multi-interfacial structures effectively limit continuous growth of single (200)-preferred orientation coarse columnar TiN crystals. The hardness of the coatings increases with the decreasing bilayer periods. Multi-interface can act as a lubricant, effectively hinder the cracks propagation and prevent aggressive seawater from permeating to substrate through the micro-pores to some extent, reducing the friction coefficient and wear rates. It was found that the TiSiN/Ag multilayer coating with a bilayer period of 50 nm shows an excellent wear resistance due to the fine grain size, high hardness, and silver-lubricated transfer films formed during wear tests.     

Adaptive neuro-fuzzy approach for predicting hardness of deposited TiN/ZrN multilayer coatings

This paper presents an adaptive neuro-fuzzy approach based on first order function of fuzzy model for establishing the relationship between control factors and thin films properties of TiN/ZrN coatings on Si(100) wafer substrates. A statistical model was designed to explore the space of the processes by an orthogonal array scheme. Eight control factors of closed unbalance magnetron sputtering system were selected for modeling the process, such as interlayer material, argon and nitrogen flow rate, titanium and zirconium target current, rotation speed, work distance, and bias voltage. Analysis of variance (ANOVA) was carried out for determining the influence of control factors. In this study, with the application of ANOVA, the smallest effect of control factors was eliminated. The adaptive neuro-fuzzy inference system (ANFIS) was applied as a tool to model the deposited process with five significant control factors. The experimental results show that ANFIS demonstrates better accuracy than additive model for the film hardness. The root mean square error between prediction values and experimental values were archived to 0.04.     

The effect of postgrowth annealing on the structure and optical properties of multilayer Ge/Si heterostructures

The effect of the postgrowth laser and thermal annealing on the structure and optical properties of multilayer heterostructures comprising quantum dots of germanium in a silicon matrix has been studied by photoluminescence (PL) and transmission electron microscopy (TEM). The PL spectra of annealed samples reveal a decrease of emission from the quantum dots and display a new emission band as compared to the initial spectra. The TEM measurements show that this effect is related to smearing of the Ge-Si interface and to the appearance of a regular rectangular network of dislocations on the surface of the annealed structure.     

Intrinsic stresses and stress relaxation in TiN/Ag multilayer coatings during thermal cycling

Morphology, structure and thermal behavior of magnetron sputtered TiN/Ag multilayer thin films deposited at 150 °C with a bilayer thickness Λ in the range of 75-600 nm are characterized. The films are thermally cycled and the relationship between bilayer thickness Λ, film structure and stress development is analyzed. The results indicate that the residual stresses in the as-deposited films and the behavior during heating are determined by the morphology and the mechanical properties of the Ag interlayers. The increasing crystallite size of Ag with increasing Λ and the initial porosity in the Ag layer are the reason for significant changes in the stress-temperature behavior. While coatings with Λ = 75 nm behave like a single-phase coating up to 380 °C, coatings with higher Λ show a different behavior when exceeding the deposition temperature, which is related to the densification of the Ag layers. During cooling, all coatings exhibit linear thermo-elastic behavior, where the slope of the stress-temperature curves also depends on Λ.     

The effects of pre-implantation of steel substrates on the structural properties of TiN coatings

We have studied the effects of nitrogen pre-implantation of AISI C1045 steel substrates on the microstructure and microhardness of deposited TiN coatings. The substrates were implanted at 40 keV, to the fluences from 5 × 10¹⁶ to 5 × 10¹⁷ ions/cm², which was followed by deposition of 1.3-μm thick TiN coatings by reactive sputtering. Structural characterization of the samples was performed by standard and grazing incidence X-ray diffraction analysis, Rutherford backscattering spectroscopy and transmission electron microscopy. Microhardness was measured by the Vicker’s method. Nitrogen implantation up to 2 × 10¹⁷ ions/cm² induces the formation of Fe₂N phase in the near surface region of the substrates, which becomes more pronounced for higher fluences. Microstructure of the deposited TiN coatings shows a strong dependence on ion beam pre-treatment of the substrates. The layers grown on non-implanted substrates have a (200) TiN preferential orientation, and those grown on implanted substrates have (111) TiN preferential orientation. The change in preferred orientation of the layers is assigned to a developed surface topography of the substrates induced by ion implantation, and possible effects of distorted and altered crystalline structure at the surface. Ion implantation and deposition of TiN coatings induce an increase of microhardness of this low performance steel for more than eight times.     

X射线测量高速钢上不同厚度氮化钛涂层残余应力

采用多弧离子镀在AISIM2高速钢(HSS)上沉积了TiN硬涂层,试样中基体厚度为1mm,涂层厚度分别为3.0、5.0、7.0、9.0和11.0μm.应用X射线衍射(XRD)分析了TiN涂层中残余应力,测量了TiN(220)衍射晶面在五种不同倾斜角(Ψ=0°,20.7°,30°,37.8°和45°)下的X射线衍射峰.结果表明:在3～11μm涂层厚度范围内,TiN涂层中均表现出残余压应力且残余压应力值较大.TiN涂层中残余应力大致分布在-3.22～-2.04GPa之间,本征应力分布在-1.32～-0.14GPa,热应力约为-1.86～-1.75GPa.TiN涂层中残余应力值随涂层厚度变化是非线性增加的,随厚度增加表现出先增大后减小的变化趋势,多项式拟合后发现约在8.5μm厚时残余应力达到最大值.     

The effect of Ti preimplantation on the properties of TiN coatings on HS 6-5-2 high-speed steel

The paper presents the results of a research on the effect of Ti preimplantation in high-speed steel on the properties of TiN hard coatings. Highly polished plates of HS 6-5-2 steel were implanted with various fluencies of Ti ions and next PVD coated with TiN. The studied effects included the layer hardness, adhesion strength, wear resistance and turning tests. The adhesion strength was estimated from scratch tests. The results of investigations indicate that an increase of Ti implantation fluence reduces the strength of coating–substrate adhesion. However the turning tests show an evident improvement of the wear properties.     

Cu丝上沉积Ti/TiN多层膜的研究

铜丝可用于尿毒症患者腹膜透析置管术中的替代导丝。为了减少或消除铜离子对生物组织的损害,增加铜丝表面的生物相容性,同时又保持铜丝较好的塑性变形能力,本文采用电弧离子镀工艺在铜丝上沉积Ti/TiN多层膜。研究结果显示,镀膜铜丝表面光亮呈金黄色。沉积膜有明显的周期性层状特征,TiN相和金属Ti相周期性交替分布。其中,TiN相具有(111)晶面择优取向。沉积膜与铜丝结合良好,弯曲时镀膜铜丝没有出现微裂纹和膜脱落现象。室温消毒液浸泡和高温蒸汽消毒处理后,镀膜铜丝表面没有变化。腹膜透析置管术中使用镀膜铜丝,患者腹膜炎发生率明显降低,镀制Ti/TiN多层膜的铜丝适合应用于腹膜透析手术。     

Microstructure and mechanical properties of nanostructure multilayer CrN/Cr coatings on titanium alloy

Five different nanostructured, multilayer coatings (CrN/Cr)x8 with different thickness ratio of Cr and CrN layers were deposited by PAPVD (Plasma Assisted Physical Vapour Deposition) vacuum arc method on Ti6Al4V titanium alloy. The microstructure, chemical and phase composition of the CrN and Cr sub-layers were characterized by SEM with EDX and Cs-corrected dedicated STEM on cross-sections prepared by focus ion beam. Besides, hardness and Young's modulus of the (Cr/CrN)x8 coatings has been measured. The adhesion has been tested by scratch test method. The obtained (CrN/Cr) multilayer coatings, 5-6 μm in thickness, have homogeneous and nanocrystalline structure, free of pores and cracks. The microstructures of Cr and CrN layers consist of columnar grains below 100 nm in diameter. The hardness and Young's modulus of these coatings depend linearly on thickness ratio of Cr and CrN layers. The decrease of the thickness ratio Cr/CrN 0.81 to 0.15 results in the increase of hardness from 1275 HV to 1710 HV and Young's modulus from 260 GPa to 271 GPa.     

The structure and photoluminescence properties of ZnO/SiC multilayer film on Si substrate

ZnO/SiC multilayer film has been fabricated on a Si (111) substrate with a silicon carbide (SiC) buffer layer using the RF (radio frequency)-magnetron technique with targets of a ceramic polycrystalline zinc oxide (ZnO) and a composite target of pure C plate with attached Si chips on the surface. The as-deposited films were annealed at a temperature range of 600–1000°C under nitrogen atmosphere. The structure and photoluminescence (PL) properties of the samples were measured using X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy and PL spectrophotometry. By increasing the annealing temperature to 800°C, it is found that all the ZnO peaks have the strongest intensities, and the crystallinity of ZnO is more consistent on the SiC buffer layer. Further increase of the annealing temperature allows the ZnO and SiC layers to penetrate one another, which makes the interface between ZnO and SiC layer become more and more complicated, thus reduces the crystallinities of ZnO and SiC. The PL properties of a ZnO/SiC multilayer are investigated in detail. It is discovered that the PL intensities of these bands reach their maximum after being annealed at 800°C. The PL peaks shift with an increase in the annealing temperature, which is due to the ZnO and SiC layers penetrating reciprocally. This makes the interface more impacted and complicated, which induces band structure deformation resulting from lattice deformation.     

Corrosion behavior of nanolayered TiN/NbN multilayer coatings prepared by reactive direct current magnetron sputtering process

TiN, NbN and TiN/NbN multilayer coatings were deposited on tool steel substrates using a reactive DC magnetron sputtering process. The coatings were characterized using X-ray diffraction, nanoindentation, atomic force microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray analysis. The corrosion behavior of TiN/NbN multilayer coatings was studied in 0.5 M HCl and 0.5 M NaCl solutions using potentiodynamic polarization and compared with single layered TiN and NbN coatings. Approximately 1.5 μm thick coatings of TiN, NbN and TiN/NbN multilayers showed good corrosion protection of the tool steel substrate and multilayer coatings performed better than single layered coatings. The corrosion behavior of the multilayers improved with total number of interfaces in the coatings. In order to conclusively demonstrate the positive effect of layering, corrosion behavior of 40-layer TiN/NbN multilayers was studied at lower coating thicknesses (32–200 nm) and compared with single layer TiN coatings of similar thicknesses. The polarization data and SEM studies of these coatings indicated that the corrosion behavior improved with coating thickness and multilayers showed better corrosion resistance as compared to the single layer coatings. Other studies such as intrinsic corrosion, effects of Ti interlayer and post-deposition annealing on the corrosion behavior of the multilayer coatings are also presented in this paper. The results of this study demonstrate that nanolayered multilayers can effectively improve the corrosion behavior of transition metal nitride hard coatings.     

Ti(CN)/TiC/Al2O3/TiN多层涂层的结构和界面结合力研究

采用中温、高温复合化学气相沉积技术(MHCVD)在WC- (6％wt)Co硬质合金基体表面制备了Ti(CN)/TiC/Al2O3/TiN 多层陶瓷涂层.通过光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)和数显显微硬度计等手段分析多层陶瓷涂层的表面及断面形貌、物相组成、显微硬度;采用表面划痕实验,结合形貌观察及X射线能谱分析(EDS)研究多层陶瓷涂层/硬质合金基体的界面结合力及其影响因素.结果表明:Ti(CN)/TiC/Al2O3/TiN 多层陶瓷涂层结构均匀致密,涂层后硬质合金的显微硬度明显提高,约2600 HV,多层陶瓷涂层与基体界面结合良好,划痕实验显示临界载荷高达105 N,多层陶瓷涂层界面间的原子扩散作用对涂层/基体界面附着力有较大贡献,而涂层内部少量Ti2O3、W6Co6C 等物相的存在对提高界面结合力也有帮助.     

Tribological behavior at elevated temperature of multilayer TiCN/TiC/TiN hard coatings produced by chemical vapor deposition

Multilayer hard coatings of TiCN/TiC/TiN on high speed steel substrates were deposited using a chemical vapor deposition system. Evaluations of microstructure, wear morphology of coatings were characterized by scanning electron microscopy, and optical microscopy. Friction coefficient and wear rates of coatings were investigated using ball-on-disk tester sliding against a WC ball at a constant load of 20 N. Tribological behavior of the coatings at room and elevated temperature were discussed. Different changing tendency of friction coefficient were observed from ball-on-disc experiments. Results showed that the friction coefficient of coatings increased gradually to a highest value, then to a relatively constant value at room temperature dry sliding wear. The friction coefficient exhibited a reverse variation tendency at temperature of 550 °C. It got a higher value at the first sliding friction cycles. Then the value of friction coefficient decreased, suffered irregular oscillations and kept a relatively lower value with increasing sliding time. Reasons of the variation of friction coefficient with sliding time and wear mechanism were analyzed and discussed at room and elevated temperatures, respectively.     

The effect of impregnation with nanostructured boehmite on the structure and properties of plasma-sprayed ceramic coatings

It is shown that capillary phenomena can be used to nanostructure ceramic coatings via their impregnation with suspensions based on a nanostructured material. Boehmite with particle sizes of 30–50 nm was used as the nanostructured material. Two methods are suggested. When already-formed coatings are impregnated, the system of interconnected pores between particles is used, with the pores within the particles themselves being closed. If hydroxyapatite particles are impregnated before the spraying, boehmite is more uniformly and to a fuller extent distributed within the plasma-sprayed coating. In contrast to the first method, a coating is nanostructured in this case both within hydroxyapatite particles and on their surface. The adhesion increases from 8.4 to 17.1 MPa upon nanostructuring.     

Effect of heat treatment on mechanical properties and microstructure of CrN/AlN multilayer coatings

Polycrystalline CrN/AlN multilayer coatings were deposited by RF magnetron sputtering on silicon (001) substrates. The bilayer periods of CrN/AlN were controlled from 4 nm to 20 nm by the use of shutters, which were adjusted by a programmable logic control (PLC). To evaluate the thermal stability, the films were annealed at 500 °C, 600 °C, 700 °C, 800 °C, and 850 °C, for 1 h in both vacuum and air environments. The phase transformation during thermal evolution was studied by X-ray diffraction (XRD). The microstructure of CrN/AlN multilayer coatings as-deposited and after annealing was observed by transmission electron microscopy (TEM). The hardness of as-deposited CrN/AlN coating with a period of 4 nm was 28.2 GPa, which was 60% higher than that predicted by the rule of mixtures. The hardness of CrN/AlN multilayer coatings annealed at 850 °C in vacuum remained similar to the as-deposited state, and the nano-layered structure still persisted. The thermal stability of CrN/AlN coatings was better than that of CrN coating. The hardness degradation ratio of CrN/AlN coating with modulation period of 4 nm was only 8.1% at 700 °C, which was superior to that of a simple CrN coating.