铀表面非平衡磁控溅射离子镀Ti基薄膜的组织结构与腐蚀性能

金属铀的化学性质十分活泼,极易发生氧化腐蚀。本文采用磁过滤多弧离子镀在金属铀表面制备Ti过渡层,然后采用非平衡磁控溅射离子镀技术制备了Ti、TiN单层膜及Ti/TiN多层薄膜,以期改善基体的抗腐蚀性能。采用X射线衍射、极化曲线、盐雾腐蚀试验对镀层的结构、表面形貌、抗腐蚀性能进行了分析。结果表明,采用磁控溅射在金属铀表面制备一层Ti/TiN多层膜后,多层膜界面较清晰,大量的界面可终止柱状晶的生长,细化晶粒,提高镀层的致密性,有效地改善了基体的抗腐蚀性能。     

Preparation of multilayered nanocrystalline thin films with composition-modulated interfaces

The properties of multilayer thin film structures depend on the morphology and structure of interfaces. A broad interface, in which the composition is varying, can enhance, e.g., the hardness of multilayer thin films. In the present experiments multilayers of TiAlN and CrN as well as TiAlN, CrN and MoS₂ were studied by using unbalanced magnetron sputter sources. The sputter sources were arranged side by side on an arc. This arrangement permits development of a transition zone between the layers, where the composition changes continuously. The multilayer system was deposited by one-fold oscillating movement of substrates in front of sputter sources. Thicknesses of layers could be changed both by oscillation frequency and by the power applied to sputter sources. Ti/Al: 50/50 at%, pure chromium and MoS₂ targets were used in the sputter sources. The depositions were performed in an Ar–N₂ mixture at 0.22 Pa working pressure. The sputtering power of the TiAl source was feed-back adjusted in fuzzy-logic mode in order to avoid fluctuation of the TiAl target sputter rate due to poisoning of the target surface. Structure characterization of films deposited on 1 0 0 Si wafers covered by thermally grown SiO₂ was performed by cross-sectional transmission electron microscopy. At first a 100 nm thick Cr base layer was deposited on the substrate to improve adhesion, which was followed by a CrN transition layer. The CrN transition layer was followed by a 100 nm thick TiAlN/CrN multilayer system. The TiAlN/CrN/MoS₂ multilayer system was deposited on the surface of this underlayer system. The underlayer systems Cr, CrN and TiAlN/CrN were crystalline with columnar structure according to the morphology of zone T of the structure zone models. The column boundaries contained segregated phases showing up in the under-focused TEM images. The surface of the underlayer system was wavy due to dome-shaped columns. The nanometer-scaled TiAlN/CrN/MoS₂ multilayer system followed this waviness. Crystallinity of the TiAlN and CrN layers in the multilayer system decreases with increasing thickness of the MoS₂ layer.     

Mechanical and tribological properties of Ti/TiAlN duplex coatings on high and low alloy tool steels

In this research work, different steels were hardened using plasma nitriding process in an Arc-PVD device. Afterwards, on both non-nitrided and plasma nitrided substrates, different Ti/TiAlN multilayer coatings were deposited by a magnetron sputtering device. Scratch tests were performed on the duplex systems in order to characterize their adhesive properties. The failure modes of individual coating systems under various normal loads were described using light optical microscope. Furthermore, to study the effect of plasma nitriding on the friction coefficient and wear rate of the systems, ball-on-disc tests were carried out. It was shown that high and low alloy tool steels obtained different levels of hardness after plasma nitriding process. The results of scratch tests showed that both Ti/TiAlN multilayer coatings have a higher adhesion to plasma nitrided steels compared to non-nitrided steels. In addition, plasma nitriding of the substrates resulted in an increase in the wear rates of multilayer coatings. It was also revealed that the adhesion and the tribology of multilayers depend strongly on the amount of titanium interlayers. An increase of the thickness of titanium interlayers enhanced the adhesion of multilayers. However, increasing the thickness of titanium interlayers decreased the hardness and wear resistance of multilayers.     

钛合金表面Ti-TiN-Zr-ZrN多层膜制备及性能

采用多靶位真空阴极电弧沉积技术,在TC11钛合金表面制备24周期的Ti-TiN-Zr-ZrN软硬交替多元多层膜。用扫描电镜、X射线衍射仪、显微硬度计、结合力划痕仪、球-盘摩擦磨损试验仪、砂粒冲刷试验仪和3D表面形貌仪,研究多层膜的表面及截面形貌、相结构、厚度、硬度、膜/基结合力、摩擦磨损性能和抗砂粒冲蚀性能。结果表明:所制备TiTiN-Zr-ZrN多层膜厚度约为5.8μm,维氏显微硬度为28.10GPa,膜基结合力为56N;TC11钛合金表面镀多层膜后耐磨性提高了一个数量级,体积磨损率由7.06×10~(-13) m~3·N~(-1)·m~(-1)降低到3.03×10~(-14) m~3·N~(-1)·m~(-1);多层膜软硬层交替的结构,受砂粒冲蚀时裂纹扩展至金属软层时应力的缓冲而出现偏转,对TC11钛合金有良好的抗砂粒冲蚀保护作用。     

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.     

Glow discharge optical emission spectroscopy for accurate and well resolved analysis of coatings and thin films

In the last years, glow discharge optical emission spectrometry (GDOES) gained more and more acceptance in the analysis of functional coatings. GDOES thereby represents an interesting alternative to common depth profiling techniques like AES and SIMS, based on its unique combination of high erosion rates and erosion depths, sensitivity, analysis of nonconductive layers and easy quantification even for light elements such as C, N, O and H. Starting with the fundamentals of GDOES, a short overview on new developments in instrument design for accurate and well resolved thin film analyses is presented.The article focuses on the analytical capabilities of glow discharge optical emission spectrometry in the analysis of metallic coatings and thin films. Results illustrating the high depth resolution, confirmation of stoichiometry, the detection of light elements in coatings as well as contamination on the surface or interfaces will be demonstrated by measurements of: a multilayer system Cr/Ti on silicon, interface contamination on silicon during deposition of aluminum, Al₂O₃-nanoparticle containing conversion coatings on zinc for corrosion resistance, Ti₃SiC₂ MAX-phase coatings by pulsed laser deposition and hydrogen detection in a V/Fe multilayer system. The selected examples illustrate that GDOES can be successfully adopted as an analytical tool in the development of new materials and coatings. A discussion of the results as well as of the limitations of GDOES is presented.     

Thermal cyclic response of EB PVD yttria-stabilized zirconia/CoCrAlY coatings

Thermal cyclic tests were conducted with plane corset-type specimens from five superalloys with EB PVD ZrO₂ + 8wt.%Y₂O₃/CoCrAlY two and three with (plastic layer) layers coatings. Testing of specimens made of differently deformed and cast alloys with three-layer coatings has shown the efficiency of the plastic layer. The characteristic feature of the ceramic layer obtained with appropriate regard for the procedure of its application is safe adhesion between the ceramic and metallic layers, as was revealed during testing. Spallation of the ceramic layer was not observed before the destruction of specimens, when there was no cracks formation in the layers and when there appeared single and multiple cracks. Variants of damage formation and damage growth in multilayer coatings were considered.     

Designing multilayer diamond like carbon coatings for improved mechanical properties

New multilayer coatings were produced by incorporating alternating soft and hard DLC layers enabled by varying the bias voltage during deposition process while maintaining a constant hard-to-soft layer thickness ratio.These coatings were deposited onto a Cr/Cr Cxgraded layer by closed field unbalanced magnetron sputtering(CFUBMS).The cross-sectional analysis of the coatings showed that the multilayer coatings possess sharp interfaces between the soft and hard layers with the hard to soft layer thickness ratio(1:1.33)constant in all the coatings.Raman analysis uncovered the increasing sp³character of the DLC coatings as a result of decreasing ID/IGratio and increasing full width at half maximum(FWHM)values of the G band peak induced supposedly by an increase in bias voltage during hard layer deposition.Nanoindentation tests showed an increase in hardness of the DLC coatings which can be correlated with the increase in the sp³content of the coatings as well as decreasing sp²-C cluster size,as calculated from the ID/IGratio.Furthermore,the coatings exhibited excellent plastic deformation resistance and adhesion strength upon microindentation and scratch testing,respectively.Although further investigations are required to assess coating durability,the multilayer design could offer the DLC coatings with a rare opportunity to combine the high hardness with damage resistance with a constant bilayer thickness and without the need to introduce complex multilayer system.     

The effect of nanolayer thickness on the structure and properties of multilayer TiN/MoN coatings

The effect of nanolayer thickness on the structure and properties of nanocomposite multilayer TiN/MoN coatings is revealed. The multilayer (alternating) TiN/MoN coatings are prepared by the Arc-PVD method. The selected thickness of the nanolayers is 2, 10, 20, and 40 nm. The formation of two phases—TiN (fcc) and γ-Mo₂N—is found. The ratio of Ti and Mo concentrations varies with varying layer thickness. The maximum hardness value obtained for different thicknesses of the layers does not exceed 28–31 GPa. The stability of TiN/MoN during cutting and tribological tests is significantly higher than that of products with TiN coatings. The nanostructured multilayer coatings with layer thicknesses of 10 and 20 nm exhibit the lowest friction coefficient of 0.09–0.12.     

A computer simulation of the time dependence of the erosion of Pyrex glass by glass beads

With the aid of scanning electron microscopy (SEM) observations of the surface of Pyrex glass, eroded by spherical glass beads, a recursive algorithm has been formulated which predicts the weight-loss from the specimen as a function of time. This method takes into account three mechanisms of material removal: material chipped off when cone cracks form on the surface; materials removed due to interaction of cone cracks on the flat surface; and materials removed due to chipping of exposed cone frustrums and the underlying rough surface. Multi-particle erosion tests were performed on the Pyrex glass target material employing spherical glass beads as impacting particles. Four different particle velocities and average particle sizes were employed as the varaibles in the experiments. An analysis of the experimental results in conjunction with the mathematical model showed a very good agreement between experimental results and theoretical prediction.     

真空管式太阳能集热器研究最新进展

从选择性吸收涂层的材料、结构、热稳定性及真空环境等方面综述了真空管式太阳能集热器的研究进展。不锈钢、Ti、Al、Ni类材料适于制备中低温选择性吸收涂层;而Mo和W类等高熔点材料,适于高温涂层。涂层结构方面,主要有吸收层/介质减反层的光干涉类、金属红外反射层/金属介质吸收层/介质减反层的金属陶瓷类。影响涂层热稳定性的主要因素是高温下涂层的破裂、氧化及元素扩散,涂层厚度与结构也能影响热稳定性。结果表明:①选择性吸收涂层制备,应采用电化学或磁控溅射技术并结合纳米材料对涂层进行多层化、梯度化研究;②应着重发展Mo类金属陶瓷型的热稳定性好的涂层,以实现高温高效集热;③应加快实现太阳能集热器的智能化、自动化与建筑一体化。     

TiN/Ti多层膜调制比对摩擦磨损行为影响的研究

考察了TiN/Ti多层膜调制比对其摩擦磨损行为的影响. 采用磁过滤阴极弧沉积的方法制备了具有不同调制比的TiN/Ti多层膜, 用扫描电镜和透射电镜对其层状结构及子层结构进行了观察和分析. 用纳米压痕和SRV摩擦磨损试验的方法, 对多层膜进行了纳米硬度和弹性模量测试以及摩擦磨损实验. 结果表明, 所制备的TiN/Ti多层膜层状结构清晰, 与基底结合良好, 调制比对多层膜的硬度和磨损特性影响较大, 而对摩擦系数的影响却不明显. 结合实验结果, 讨论了硬度与弹性模量的比值(H/E值)对TiN/Ti多层膜耐磨性的影响.     

Corrosion resistance of multilayer coatings of nanolayered Cr/Ni electrodeposited from Cr(III)-Ni(II) bath

In this study the corrosion resistance of chromium and nickel single layers and multilayer coatings of nanolayered Cr/Ni, electrodeposited from Cr(III)-Ni(II) baths on low carbon steel substrates, has been studied. The coatings were electrodeposited from a bath using pulse current and modulated agitation. The total thickness of single layer and multilayer coatings was fixed at 5 μm and multilayer coatings with different modulation wavelengths and Cr to Ni thickness ratio were electrodeposited. Corrosion behavior of coatings was then studied by using potentiodynamic polarization test and electrochemical impedance spectroscopy in 0.1 M H₂SO₄. The results showed that Cr and Ni single layers had low corrosion resistance due to the presence of surface cracks and pores, respectively. On the other hand, optimized 20 nm Cr/50 nm Ni multilayer deposition significantly improved corrosion resistance.     

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.     

A hybrid experimental/numerical approach to characterize interfacial adhesion in multilayer low-κ thin film specimens

The strength of multilayer low dielectric (low-κ) constant organo-silicate glass (OSG) and silicon-carbon-nitride (SiCN) thin film interfaces is characterized by a laser spallation technique. Two specimen sets with different OSG/SiCN stacking sequences are evaluated. The effect of helium (He) pretreatment is also investigated. The stress at the low-κ interface is enhanced through the use of a fused silica backing layer to shape the incident pulse and the addition of a thin gold (Au) top layer to increase inertial force during the dynamic failure event. The weakest interface in the multilayer stack (first to fail) is identified through optical images, profilometry and scanning electron microscope images of the spallation zone. The strength of the failed interface is inferred from the incident stress history in combination with a one dimensional dynamic wave propagation analysis. The adhesion strength of the OSG/SiCN interface (372 MPa) is 32% larger than that of Si/OSG (282 MPa) for specimens with no He pretreatement. The interfacial strength of both interfaces is significantly increased by a He pretreatment, making failure by spallation difficult.     

TiN/Ti多层膜韧性对摩擦学性能的影响

考察了TiN/Ti多层膜韧性对其摩擦学性能的影响.采用磁过滤阴极弧沉积的方法制备了具有不同Ti子层厚度的TiN/Ti多层膜.用透射电镜对其层状结构及子层厚度进行了观察和分析,分别用Rockwell硬度计和UMT摩擦磨损试验机,进行了压痕测试和摩擦磨损实验.结果表明,TiN/Ti多层膜中Ti子层的加人显著提高了多层膜的韧性,相对TiN单层薄膜,当载荷较大时,多层膜的耐磨性有明显的改善.结合实验结果,讨论了TiN/Ti多层膜韧性对其耐磨性的影响.     

C/C复合材料表面水热电泳沉积SiCn/SiC复合抗氧化涂层研究

采用水热电泳沉积法在SiC-C/C复合材料表面制备纳米碳化硅（SiC_n）涂层. 采用XRD和SEM对涂层的晶相组成、表面和断面的微观结构进行了表征. 主要研究了水热沉积温度对涂层的结构及高温抗氧化性能的影响, 并分析了涂层试样在1600℃的高温氧化气氛下失效行为. 结果表明：纳米碳化硅涂层主要由β-SiC组成. 涂层的致密程度和厚度随着水热沉积温度的升高而提高. 随着水热温度的提高, 涂层试样的抗氧化性能也有明显的提高. 在120℃水热沉积温度下制备的涂层试样可在空气气氛1500℃下有效保护C/C复合材料202h,而氧化失重仅为2.16×10^-3g/cm². 在1600℃下氧化64h后失重为3.7×10^-3g/cm². 其高温失效是由于长时间的氧化挥发后表面SiO2膜不能完全封填表面缺陷, 内涂层中产生了贯穿性的孔隙所致.     

CN<em>x/TiN多层复合涂层抗水蚀性能的研究

采用多弧-磁控溅射镀膜机在不锈钢2Cr13衬底上沉积CN_<em>x/TiN多层复合涂层。利用光电子能谱仪(XPS)和透射电子衍射(TED)对涂层的组成和结构进行分析。利用自行研制的高压水蚀试验装置对不锈钢、高铬铸铁、司太立合金以及CN_<em>x/TiN多层复合涂层的抗水蚀性能进行对比试验,最后对涂层的水蚀失效机理进行了探讨。试验结果表明:CN_<em>x/TiN多层复合涂层具有较高的硬度、附着力、抗热冲击性能以及优异的抗水蚀性能,是一种优良的汽轮机末级叶片抗水蚀用涂层。     

Analysis on microstructure and characteristics of TiAlN/CrN nano-multilayer films deposited by cathodic arc deposition

In this study, TiAlN/CrN multilayer thin films were deposited on SUS 403 stainless steel by cathodic arc deposition. The effects of substrate orientation (substrate surface parallel/perpendicular to target surface) and rotation speed were investigated in detail. Microstructure of the coatings was analyzed by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. Meanwhile, tribological and corrosion tests were performed. The experimental results showed that the as-deposited films exhibit a nano-scale multilayer structure consisting of TiAlN and CrN phases. The TiAlN/CrN multilayer films prepared by a parallel orientation and a rotation speed of 4 rpm not only possesses the best coating hardness and hardness/elastic modulus ratio, but also reveals superior abrasion resistance and corrosion resistance.     

Microstructures and bond strengths of plasma-sprayed hydroxyapatite coatings on porous titanium substrates

Hydroxyapatite (HA) coating was carried out by plasma spraying on bulk Ti substrates and porous Ti substrates having a Young’s modulus similar to that of human bone. The microstructures and bond strengths of HA coatings were investigated in this study. The HA coatings with thickness of 200–250 μ m were free from cracks at interfaces between the coating and Ti substrates. XRD analysis revealed that the HA powder used for plasma spraying had a highly crystallized apatite structure, while the HA coating contained several phases other than HA. The bond strength between the HA coating and the Ti substrates evaluated by standard bonding test (ASTM C633-01) were strongly affected by the failure behavior of the HA coating. A mechanism to explain the failure is discussed in terms of surface roughness of the plasma-sprayed HA coatings on the bulk and porous Ti substrates.