MICROSTRUCTURE AND INDENTATION BEHAVIOUR OF MULTILAYER Ti-N FILM

The microstructure of Ti/TiN multilayer film was studied.It was shown by trans-mission electron microscopy of cross-sectional sample and respective secondary neutralsmass-spectroscopy depth profiling that the film has a periodic alternate multilayeredstructure:substrate /FeTi/Ti/Ti_2N/TiN/Ti_2N/Ti/Ti_2N/TiN...Ti/Ti_2N/TiN,whereFeTi and Ti_2N were the transition layers formed during ion plating.Cross-sectionalfracture surface of indentation samples had been obtained and studied with scanningelectron microscopy.It was shown that the multilayer film deformed during indentation,formed an indentation pit and a pile-up of materials around the indentation pit.As theapplied load increased deformation region extended beyond the film/substratc interfaceand into the substrate,the interlayer crack in the film and hole formation at the film/substrate interface were initiated.It is also shown that the multilayered Ti/TiN filmoffered better toughness in comparison with single layer TiN film.     

Stainless Steel Bipolar Plates Deposited with Multilayer Films for PEMFC Applications

A chromium nitride (CrN, Cr₂N)/chromium (Cr)/indium-tin-oxide (ITO) system and a gold (Au)/titanium (Ti) system were separately deposited using a sputtering method and an E-beam method, respectively, onto stainless steel 316 and 304 plates. The XRD patterns of the deposited stainless steel plates showed the crystalline phase of typical indium-tin oxide and of metallic phases, such as chromium, gold, and the metal substrate, as well as those of external chromium nitride films. The nitride films were composed of two metal nitride phases that consisted of CrN and Cr₂N compounds. The surface morphologies of the modified stainless steel bipolar plates were observed using atomic force microscopy and FE-SEM. The chromium nitride (CrN, Cr₂N)/chromium (Cr)/indium-tin-oxide (ITO) multilayer that was formed on the stainless steel plates had a surface microstructural morphology that consisted of fine columnar grains 10 nm in diameter and 60 nm in length. The external gold films that were formed on the stainless steel plates had a grain microstructure approximately 100 nm in diameter. The grain size of the external surface of the stainless steel plates with the gold (Au)/titanium (Ti) system increased with increasing gold film thickness. The electrical resistances and water contact angles of the stainless steel bipolar plates that were covered with the multilayer films were examined as a function of the thickness of the ITO film or of the external gold film. In the corrosion test, ICP-MS results indicated that the gold (Au)/titanium (Ti) films showed relatively excellent chemical stability after exposure to H₂SO₄ solution with pH 3 at 80 °C.     

调制周期对TiN/Ti多层膜组织结构和结合力的影响

为了阐明调制周期对薄膜微观组织及薄膜与基体结合力的影响,采用反应磁控溅射在Ti6Al4V基板上交替沉积了Ti层及TiN层制备了TiN/Ti多层膜。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、显微硬度仪和划痕仪测量分析了薄膜的晶体结构、微观组织、硬度以及薄膜与基体之间的结合力。研究结果表明:TiN/Ti多层膜中均存在TiN,Ti和Ti2N 3种相。TiN/Ti多层膜均以柱状晶方式生长,在调制周期较大(5层)时,TiN和Ti层的界面清晰;随着调制周期的减小(层数增加),TiN和Ti层的界面逐渐消失。与单层TiN薄膜相比,多层TiN/Ti薄膜的硬度显著提高;但随着薄膜层数的增加,多层TiN/Ti薄膜硬度略微降低。当调制周期为80nm(30层)时,薄膜与基体的结合力明显提高,达到73N。     

TiN-TiB2 composite coatings reactively produced by electrothermally exploded powder spray

Composite coatings composed of titanium nitride, TiN, and diboride, TiB₂, were reactively produced by the electrothermally exploded powder spray technique, in which feedstock powder was prepared from titanium and boron nitride particles. The microstructure of the coating was composed of titanium-ceramic particles the size of which were on the order of several nanometers to a few hundred nanometers. Such reactive thermal spraying brought base-metal saturation into a coating layer at the early stages of coating formation. The ceramic composite spray using feedstock of TiN and TiB₂ particles preferentially brought a new phase of cubic titanium boronitride together with TiN and TiB₂ into a coating. On comparing such a coating to one produced by the conventional method, the reactive thermal spray coating was richer in TiN and TiB₂ due to the excess nitrogen in the feedstock.     

Microstructural effects on indentation failure mechanisms in TiN coatings: Finite element simulations

Titanium nitride (TiN) coatings offer improvements in resistance to wear and environmental degradation. TiN films produced by physical vapour deposition tend to exhibit columnar grain structures, with attendant anisotropies in elastic and fracture properties that influence mechanical behaviour during instrumented indentation. However, computational simulations of indentation behaviour to date have treated TiN films as homogeneous and isotropic. In the present study, nanoindentation of TiN coatings on ductile substrates is simulated and resultant deformation and damage mechanisms are predicted. Intergranular sliding that occurs due to the columnar grain structure is incorporated into the model via anisotropic property definitions and nodal coupling. Substrate and coating properties are calibrated by comparison with previously obtained experimental results. Effects of coating thickness, substrate ductility and residual stresses on coating deformation processes and failure mechanisms are established.     

Hardfacing of AISI304 steel: fabrication of oxide-boride-nitride ceramic matrix composite layer by laser-assisted high temperature chemical reaction

Composition, structure and properties of the products of self-propagating high-temperature synthesis (SHS) are characterised by some distinctive features. High heating rate, fast cooling after rapid completion of the reactions and steep temperature gradients make SHS very effective in producing in situ composites with ceramic reinforcements. In the present work, hardfacing of AISI304 substrates has been done by fabricating a hard ternary ceramic matrix composite layer of Al₂O₃–TiB₂–TiN by laser surface treatment at different scan speeds. The formation of the surface layer is due to laser-triggered SHS followed by laser melting. A mixture of Al, TiO₂ and hBN has been used as a precursor for the SHS reaction. The study of the microstructure of the as-fabricated composite layer reveals the co-existence of TiB₂ and TiN phases in the nanometric size range in Al₂O₃ matrix. The presence of all the phases has been confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The average grain sizes were calculated for the reinforcing phases and found to be 36 and 66?nm for TiB₂ and TiN, respectively, for the ceramic layer fabricated with a scan speed of 10?mm?s^?1, whereas 21 and 53?nm have been observed for TiB₂ and TiN, respectively, for the ceramic layer fabricated with the scan speed of 5?mm?s^?1. The understanding of the chemical synthesis in the SHS reaction mentioned here and the process of development of the reinforced composite in the fabrication of the hardfaced layer over steel surface will be immensely helpful in the discernment of the mechanical properties and, thus, finding the target area for the usage of this product. The virtues of the process and formation of the hard composite are reflected well in the microhardness achieved in the fabricated layers, as it is significantly higher than that of the substrate (AISI304 steel). In addition, indentation with a Berkovich tip in a nano-indentation set-up helped in further evaluation of the composite’s hardness and elastic modulus. The property spectrum of the composite, as reported here, indicates its suitability in various wear-intensive applications.     

Micromechanisms of damage nucleation during contact deformation of columnar multilayer nitride coatings

In order to resolve some missing micromechanistic details regarding contact deformation in nitride multilayer coatings we report here observations from cross-sectional transmission electron microscopy and focused ion beam studies of the Vickers indentations on TiN/TiAlN multilayer films of various total thicknesses as well as bilayer periods. The study of damage induced by contact deformation in a nitride multilayer coating is complemented by stress calculated using an analytical model. Kinked boundaries of sliding columns give rise to cracks which propagate at an angle to the indentation axis under a combination of compressive and shear stresses. It is seen that multilayers provide more distributed columnar sliding, thereby reducing the stress intensity factor for shear cracking, while interfacial dislocations provide a stress relief mechanism by enabling lateral movement of material.     

Extremely hard,damage-tolerant ceramic coatings with functionally graded,periodically varying architecture

Functionally graded, multilayer coatings consisting of alternating TiN/TiSiN layers were synthesized in an attempt to overcome the innate brittleness of TiSiN nanocomposite coatings, whilst maintaining high hardness. These coatings exhibited key structural characteristics that are known to render many naturally occurring materials extremely hard and robust. Transmission electron microscopy revealed that shear sliding of columnar TiN grains played a vital role in controlling the inelastic deformation of these coatings, conferring a greater resistance to contact damage. Moreover, nanoindentation experiments showed that the multilayer coatings exhibited high hardness, attributed to the strong shear resistance offered by the hard TiSiN layers. A dependence of coating hardness upon indentation penetration depth (h_t) was found to be proportional to 1/√h_t, according to a mechanistically based model, from which the shear stress was determined. The energy dissipation during indentation was also quantified to show the critical role of the shear stress, regulated by the thickness of TiSiN layers, in resisting contact damage in the coatings. Finite-element models were constructed and the presence of transgranular cracks in the monolithic TiSiN coating was clarified based upon experimental observations. Furthermore, the simulations revealed that the transition of the dominant deformation mechanism from brittle transgranular cracking to intergranular shear sliding was controlled by the microstructural characteristics of the coatings. Enabled by the shear sliding, as well as periodic changes in elastic modulus, such a functionally graded multilayer structure was effective in lowering the magnitude and extent of stress concentrations, thereby extending the damage tolerance accessible to a ceramic coating.     

铜锡钛合金炉中钎焊立方氮化硼界面微观结构

采用真空炉中钎焊的方法,应用Cu-Sn-Ti合金实现了立方氮化硼(CBN)磨粒与工具基体的钎焊连接.运用三维视频显微镜、扫描电镜(SEM)、能谱仪(EDS)及X射线衍射仪对微观形貌、元素分布和生成物物相进行了观测分析,发现活性Ti元素明显向CBN磨粒表面发生偏聚,在CBN磨粒表面生成TiN,TiB和TiB2,这些反应产...     

气相沉积 Ti / TiN 多层薄膜的力学及耐腐蚀性能研究

目的研究多层薄膜的界面对薄膜性能的影响。方法通过直流磁控溅射法在45#钢表面制备Ti N及Ti/Ti N多层薄膜,采用扫描电镜和XRD衍射分析仪对薄膜表面形貌及相结构进行观察和分析,使用纳米压痕仪、电子薄膜应力分布测试仪对Ti N及Ti/Ti多层薄膜的力学性能以及残余应力大小进行研究,并运用电化学设备对Ti N及不同调制周期的Ti/Ti多层薄膜的耐腐蚀性能进行研究。结果制备的Ti N及Ti/Ti N多层薄膜表面光滑且结构致密,Ti N晶粒细小且为非晶相;薄膜力学性能良好,内部均存在残余压应力。随着调制周期的减小,弹性模量和硬度先减小后增大,内部残余应力逐渐减小且分布不均匀程度逐渐增大。薄膜在H_2SO_4中的腐蚀试验表明:当Ti/Ti N多层薄膜调制周期为1μm时,多层薄膜的耐腐蚀性能不如Ti N薄膜,随着Ti/Ti N多层薄膜随调制周期的减小,多层薄膜的耐腐蚀性能逐渐升高;当调制周期为0.5μm时,Ti/Ti N多层薄膜的耐蚀性能已超过Ti N薄膜。结论 Ti/Ti N多层薄膜界面的增多有助于减小薄膜的残余应力,并且可提高薄膜的耐蚀性能。     

Evaluation of nanocrystalline TiN films prepared by arc ion plating

Monolayer and multilayer TiN films were synthesized on a SKD 11 steel sheet by an arc ion plating technique and the correlation between the microstructure and properties of the TiN films was comparatively investigated. The results indicated that the main phase was fcc-TiN, showing a (200) preferred orientation in the film under 2.0 × 10⁻¹ torr N₂ partial pressure, whereas a gradual transition to (111) preferred orientation was observed with decreasing N₂ partial pressure to 1.4 × 10⁻¹ torr. The (200) and (111) textures in the film under an arc current of 80 A were found to be competitive orientations, but the (200) texture became stronger as the arc current was increased. Compared to the optimal monolayer TiN films, the multilayer TiN film possessed high hardness of up to 20.3 ± 1.3 GPa and excellent wear resistance. These features are attributed to the presence of dense microstructures that are mainly composed of TiN phase and are around 1.7 μm to 1.8 μm in thickness.     

Finite element and dimensional analysis algorithm for the prediction of mechanical properties of bulk materials and thin films

In this work, the applicability of a new algorithm for the estimation of mechanical properties from instrumented indentation data was studied for thin films. The applicability was analyzed with the aid of both three-dimensional finite element simulations and experimental indentation tests. The numerical approach allowed studying the effect of the substrate on the estimation of mechanical properties of the film, which was conducted based on the ratio h_max/l between maximum indentation depth and film thickness. For the experimental analysis, indentation tests were conducted on AISI H13 tool steel specimens, plasma nitrated and coated with TiN thin films. Results have indicated that, for the conditions analyzed in this work, the elastic deformation of the substrate limited the extraction of mechanical properties of the film/substrate system. This limitation occurred even at low h_max/l ratios and especially for the estimation of the values of yield strength and strain hardening exponent. At indentation depths lower than 4% of the film thickness, the proposed algorithm estimated the mechanical properties of the film with accuracy. Particularly for hardness, precise values were estimated at h_max/l lower than 0.1, i.e. 10% of film thickness.     

Mechanochemical synthesis of TiN/TiB2/Ti-silicide nanocomposite powders and their thermal stability

Extremely fine and homogeneous TiN/TiB₂/Ti-silicide composite powders have been synthesized from mixtures of Ti, BN and Si₃N₄ powders by high-energy ball milling through a mechanically activated self-sustaining reaction. They have a microstructure consisting of TiN and TiB₂ crystallites of less than 15 nm embedded in amorphous TiSi₂ or Ti₅Si₃ matrix. When these nanocomposite powders were annealed at high temperatures, the microstructure did not change significantly and TiN and TiB₂ mutually suppressed the grain growth of both phases effectively.     

Preparation,characterization and electrochemical properties of boron-doped diamond films on Nb substrates

A series of boron-doped polycrystalline diamond films were prepared by hot filament (HF) chemical vapor deposition on Nb substrates. The effects of B/C ratio of reaction gas on film morphology, growth rate, chemical bonding states, phase composition and electrochemical properties of each deposited sample were studied by scanning electron microscopy, Raman spectra, X-ray diffraction, microhardness indentation, and electrochemical analysis. Results show that the average grain size of diamond and the growth rate decrease with increasing the B/C ratio. The diamond films exhibit excellent adhesion under Vickers microhardness testing (9.8 N load). The sample with 2% B/C ratio has a wider potential window and a lower background current as well as a faster redox reaction rate in H₂SO₄solution and KFe(CN)₆ redox system compared with other doping level electrodes.     

低模量Ti6Al4V表面Ti(Al/Pt)N薄膜强化改性

为解决硬质薄膜因与软基体硬度和模量差较大导致的薄膜失效问题,提高硬质薄膜在Ti6Al4V(TC4)钛合金基体上的适应性,使用掺杂氮化钛（TiN）陶瓷薄膜对低模量Ti6Al4V合金表面强化。采用热丝增强等离子体磁控溅射技术在Ti6Al4V合金表面制备Ti(Al/Pt)N薄膜：包括本征TiN、Al&Pt掺杂TiAlN和TiAl(Pt)N薄膜。采用扫描电子显微镜、X-射线衍射仪、纳米压痕仪、洛氏硬度计和摩擦磨损测试仪分别表征三种薄膜组织形貌、能谱分析、相结构和内应力、纳米硬度和模量及耐磨性。结果表明：Al元素掺杂使TiN薄膜柱状晶细化,截面形貌柱状晶更致密;同时微量Pt掺杂后,截面断口呈韧性撕裂。本征TiN和TiAlN薄膜衍射峰图谱呈现TiN(111)取向,TiAl(Pt)N薄膜的衍射峰呈TiN(200)主峰位。Al元素掺杂使TiN薄膜晶格畸变增多,内应力从-13 MPa增大到-115 MPa,导致膜-基结合力恶化,洛氏压痕和摩擦磨损实验中均出现薄膜剥落。Pt掺杂后薄膜内应力降低到-66 MPa,在洛氏压痕试验中TiAl(Pt)N薄膜与基体结合良好,仅有少许环形裂纹。摩擦磨损试验中本...     

FeGaB (25 nm)/Al2O3/FeGaB(25 nm)多层薄膜结构：氧化铝(Al2O3)厚度变化对静态与动态磁性能的影响

铁镓(FeGa)薄膜与其它软磁材料相比具有较大的磁致伸缩常数,在设计集成磁性传感器芯片中具有独特的优势,本文通过采用非磁性掺杂和多层膜方法来控制这种合金薄膜的磁学与电学性能参数。我们实验发现在掺杂一定量硼(B)元素后,厚度小于30 nm的FeGa薄膜顽力可以得到显著降低,而对于较厚薄膜在插入超薄Al2 O3中间层后软磁性能可以得到同样程度显著改善,同时饱和磁化(Ms)变化可忽略。对于我们制备的FeGaB (25 nm)/Al2O3(0.5 nm)/FeGaB(25 nm)多层膜,其易轴矫顽力可以小到0.98 Oe,电阻率与50nm单层FeGaB膜相比增加了1.5倍,同时具有吉赫兹高磁导率谱。样品微结构分析表明,磁性颗粒结晶质量和物理尺寸的减小对软磁性改善起到重要作用,另外我们也讨论分析了静磁相互作用和表面形貌对磁畴运动及矫顽力的影响。本文发展的掺杂与多层膜混合方案来来增强电磁性能的方法,也可应用于其他类型的软磁材料系统。     

Structural and hardness studies of CN X /TiN composite coatings on Si (100) substrates by laser ablation method

CN _x /TiN composite coatings were deposited on Si (100) substrates using the pulsed laser deposition (PLD) method. Previous results showed that a seed of titanium nitride (TiN) layer between silicon substrates and a top layer of carbon nitride increased the hardness and modulus values of overall composite coatings (Ref 1). This paper describes the same approach to growing carbon nitride composite coatings with varying thicknesses of different kinds of buffer layers and carbon nitride films on Si (100) substrates at different temperatures and pressures. Preliminary results showed the presence of carbon nitride films by the Fourier transform infrared spectroscopy (FTIR) method. The mechanical properties of the films were characterized using the nanoindentation technique. The crystallographic properties of the films were characterized using the x-ray diffractometer method.     

Magnetron sputtering deposition Ti-B-C-N films by Ti/B4C compound target

Ti-B-C-N films were deposited by unbalanced DC magnetron sputtering with Ti/B₄C compound target. The sputtering zone in the surface of the target was adjusted by a magnetic coil. X-ray photoelectron spectrum, X-ray diffraction, nano-indentation and scratch tests were used to analyze the film composition, phase structure, hardness, modulus and scratch resistance. The results showed that the composition of the Ti-B-C-N films can be adjusted by changing deposition parameters, such as gas ratio of N₂ to Ar and the magnetron coil current. The main crystal phase in the films was TiB₂. The proportion of crystalline TiB₂ decreased with the increasing of N₂ partial pressure and reached a maximum value at 300 mA magnetic coil current, when the coil current changed from 200 mA to 500 mA. The films containing more TiB₂ proportion showed higher hardness and modulus. The scratch resistance of the films increased with the films hardness.     

Ti(C,N)复合膜和TiN/Ti(C,N)多层膜组织和显微硬度

采用非平衡反应磁控溅射的方法在Si(100)基片上沉积Ti(C,N)复合膜和不同调制周期、调制比的TiN/Ti(C,N)纳米多层薄膜。薄膜的微观结构和力学性能采用X射线衍射仪(XRD)、显微硬度计进行表征。结果表明,Ti(C,N)复合膜的微观结构和力学性能与掺入C的含量有关;TiN/Ti(C,N)纳米多层膜的微观结构和力学性能与调制周期和调制比有关,其显微硬度在一定的调制周期和调制比范围内出现了超硬现象。Ti(C,N)、TiN/Ti(C,N)均为δ-NaCl面心立方结构;Ti(C,N)复合膜显微硬度提高是因为固溶强化,TiN/Ti(C,N)纳米多层膜硬度的提高主要是共格外延生长在界面处产生的交变应力场。     

钛合金表面氩弧熔覆原位合成TiB2-TiN涂层组织及耐磨性能

以BN和Ni60A合金粉末为熔覆材料,采用氩弧熔覆技术在TCA合金表面原位合成TiB2-TiN增强颗粒耐磨涂层．利用x射线衍射仪、扫描电子显微镜和摩擦磨损试验机对熔覆层的组织和性能进行分析测试．结果表明,复合涂层的显微组织沿层深方向分为熔覆区、结合区和热影响区;熔覆层与基体呈良好冶金结合,TiB2-TiN颗粒弥散分布,...