Study on high-temperature oxidation behaviors of Cr–Si–N films

The high-temperature oxidation behavior of CrN and Cr–Si–N films was investigated. These films were deposited on STS 304 substrates by a hybrid deposition system with arc ion plating (AIP) and DC magnetron sputtering method using separate Cr (99.99%) and Si (99.99%) targets in a gaseous mixture of Ar and N₂. Good oxidation resistance of the CrN film was further improved by the incorporation of Si into the CrN film. The oxidation products of the Cr–Si–N film were Cr₂O₃ and amorphous SiO₂, which were gradually formed by the outward diffusion of Cr, Si, and N as well as the inward diffusion of oxygen. The oxidation kinetics of the specimen showed parabolic behavior, indicating that the diffusion process prevailed during oxidation. The oxidation activation energies for CrN, CrSi_0.10N, and CrSi_0.15N coatings are 303.8, 316.4, and 333.9 kJ/mol, respectively.     

Characterisation and tribological evaluation of nitrogen-containing molybdenum–copper PVD metallic nanocomposite films

This paper reports on the structural, mechanical and tribological properties of molybdenum–copper nanocomposite films ‘doped’ with small amounts of nitrogen, which contain either no nitride phase (i.e. the nitrogen is held in interstitial solid solution, mainly in molybdenum) or small amounts of lower nitrides (i.e. Mo₂N). All films were deposited on Si wafers, AISI M2 high speed steel and AISI 316 stainless steel by reactive sputtering using a hot-filament-enhanced dc unbalanced magnetron system. A systematic approach was adopted to investigate the evolution of metal/metal and ceramic/metal phase combinations with increasing nitrogen content (up to 40 at.% N) in the film. Coating composition and microstructure were determined by cross-sectional TEM, SEM and XPS. XRD was used to identify (where possible) metallic and metal-nitride phases. Mechanical properties such as hardness and elastic modulus were determined by low load Knoop and instrumented Vickers indentation measurements. Reciprocating sliding, micro-abrasion and impact tests were performed to assess tribological performance.

It was found that increasing the nitrogen gas flow rate from 0 to 15 sccm (and therefore nitrogen content in the film from 0 to 24 at.% N), refined significantly the coating microstructure from columnar to a dense and more equiaxed morphology, increasing the hardness whilst maintaining (almost constant) elastic modulus values, close to that of molybdenum metal. Further increases in the nitrogen gas flow rate resulted in films that appeared to contain significant fractions of the Mo₂N ceramic phase. SEM and cross-sectional TEM analyses of the film deposited at a nitrogen flow rate of 20 sccm (containing 36 at.% N) demonstrated a microstructure consisting of 50–100 nm wide columns, which contain small regions of contrast in dark-field images, of the order of 3–5 nm wide. A maximum hardness of 32 GPa and the highest hardness/modulus ratio was however found in the (predominantly metallic) film deposited at a nitrogen gas flow rate of 15 sccm. This film also performed best in both micro-abrasion and impact wear tests; in contrast, the ‘ceramic’ film (deposited at 20 sccm nitrogen flow rate) performed better in reciprocating sliding wear.     

Mechanical properties of nano-structured Ti-Si-N films synthesized by cathodic arc evaporation

Ti_1−xSi_xN coatings were synthesized by cathodic arc evaporation with plasma-enhancing filter duct, using Ti₈₀Si₂₀ alloy target as cathodes. Optical emission study revealed that excitation, ionization and charge transfer reactions of the Ti-Si-N plasma occurred during the Ti_1−xSi_xN deposition process. The chemical content of Si varied from 3.3 to 6.0 at% in Ti_1−xSi_xN depending on the nitrogen partial pressure of the reaction chamber. All the Ti_1−xSi_xN coatings displayed a NaCl structure and a preferred (2 0 0) orientation parallel to the substrate surface. Among the studied Ti_1−xSi_xN coatings, the Ti_1−xSi_xN with 6 at.% Si possessed the highest hardness of 45 GPa and H³/E*² ratio of 0.527 GPa, indicating the best resistance to plastic deformation. We found that the structure and mechanical properties of the Ti_1−xSi_xN films were correlated with the nitrogen pressure and silicon content of the coatings.     

Al含量对Cr1–xAlxN涂层力学、热稳定性、抗氧化性及耐蚀性的影响

目的探讨Al含量对Cr_1–xAl_xN涂层结构和性能的影响。方法在阴极弧蒸发设备中,分别采用Cr、Cr_0.70Al_0.30、Cr_0.50Al_0.50、Cr_0.40Al_0.60和Cr_0.30Al_0.70靶材制备5种不同Al含量的Cr_1–xAl_xN涂层。借助能量色散X射线光谱仪(EDX)、X射线衍射仪(XRD)、纳米压痕仪、扫描电子显微镜(SEM)和电化学工作站对Cr_1–xAl_xN涂层的成分、结构、力学性能、热稳定性、抗氧化性和耐蚀性进行研究。结果5种Cr_1–xAl_xN涂层均呈单相面心立方结构,其硬度随Al含量的增加而提升,由CrN的(16.9±0.8)GPa升至Cr_0.75Al_0.25N的(25.1±0.7)GPa、Cr_0.56Al_0.44N的(27.0±1.1)GPa、Cr_0.46Al_0.54N的(28.5±1.5)GPa和Cr_0.36Al_0.64N的(30.4±0.8)GPa。所有涂层在1000℃退火后,开始出现六方h-Cr2N的衍射峰,其衍射峰强度随Al含量的上升而降低。Cr_0.75Al_0.25N、Cr_0.56Al_0.44N和Cr_0.46Al_0.54N涂层在1100℃退火后,可检测到六方纤锌矿结构w-AlN相,而高Al含量Cr_0.36Al_0.64N涂层在1000℃退火后,便可检测到w-AlN相。在1000℃氧化15 h后,CrN涂层已经完全氧化,Cr_0.75Al_0.25N、Cr_0.56Al_0.44N、Cr_0.46Al_0.54N和Cr_0.36Al_0.64N涂层的氧化层厚度分别约为0.4、0.3、0.3、0.2μm;在1100℃氧化15 h后,CrN、Cr_0.75Al_0.25N和Cr_0.56Al_0.44N涂层已完全氧化,而Cr_0.46Al_0.54N和Cr_0.36Al_0.64N涂层的氧化层厚度分别约为2.5、1.4μm。CrN、Cr_0.75Al_0.25N、Cr_0.56Al_0.44N、Cr_0.46Al_0.54N和Cr_0.36Al_0.64N涂层在3.5%的NaCl溶液中测得的极化电阻分别为567.69、5.34、71.80、160.10、92.56 k?·cm²。结论涂层的硬度和抗氧化性随Al含量的增加而提升。Al的加入在抑制Cr—N分解的同时,促进了涂层中w-AlN的生成。CrN涂层具有最优的耐蚀性,而在含Al涂层中,涂层的耐蚀性随Al含量的增加呈现出先上升、后下降的趋势。     

正向电压对镁合金微弧氧化膜层相结构的影响

采用微弧氧化技术,以30g/L的磷酸钠为电解液,利用系统的XRD手段研究了正向电压对AZ31镁合金表面微弧氧化膜层不同厚度的相组成,计算出晶粒尺寸、晶面间距和残余应力的分布规律.结果表明:电压不同膜层中各深度相的衍射峰强度、相组成和结晶度都不同,其中Mg3(PO4)2 (200)峰的晶粒尺寸随电压增加而变粗,且同一电压制备的膜层在同一晶向不同厚度的晶粒尺寸不一样,其值呈至膜层表面距离减小而减小,晶面间距也呈减小趋势;MgO相组成的涂层残余应力处于拉应力,其值随电压增加而显著减小.     

Effect of Axial Magnetic Field on the Microstructure and Mechanical Properties of CrN Films Deposited by Arc Ion Plating

CrN films were deposited on the high-speed-steel substrates by arc ion plating. The effect of an axial magnetic field on the microstructure and mechanical properties was investigated. The chemical composition, microstructure, surface morphology, surface roughness, hardness and film/substrate adhesion of the film were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope(SEM), surface morphology analyzer, Vickers microhardness test and scratch test. The results showed that the magnetic field puts much effect on the microstructure,chemical composition, hardness and film/substrate adhesion of the Cr N films. The N content increases and Cr content decreases when the magnetic flux density increases from 0 to 30 m T. All of the Cr N films were found to be substoichiometric. With an increase in the magnetic flux density, the film structures change in such way: Cr_2N →Cr_(2-N)+CrN→CrN+Cr_2N→CrN.The SEM results showed that the number of macroparticles(MPs) on the film surface is significantly reduced when the magnetic flux density increases to 10 mT or higher. The surface roughness decreases with the magnetic field, which is attributed to the fewer MPs and sputtered craters on the film surface. The hardness value increases from 2074 HV_(0.025) at 0 mT(without magnetic field) and reaches a maximum value of 2509 HV_(0.025) at 10 m T.The further increase in the magnetic flux density leads to a decrease in the film hardness. The critical load of film/substrate adhesion shows a monotonous increase with the increase in magnetic flux density.     

硬质合金基体上金刚石膜的XRD研究

采用直流等离子体射流CVD法在硬质合金 (WC + 8wt.%Co)基体上生长金刚石膜 ,主要借助XRD分析方法对CVD金刚石膜的微观结构和残余应力进行了研究 ,探讨了CVD金刚石膜中残余应力的形成及其对金刚石膜粘附性能的影响。研究结果表明 :CVD金刚石膜中通常存在GPa数量级的残余压应力 ,膜中存在适中的残余压应力 ,有利于CVD金刚石膜获得最佳的粘附性能     

Stress analysis of high temperature ZrO2 insulation coatings on Ag using finite element method

The aim of this study is to investigate residual stresses occurred during cooling procedure of ZrO₂ insulation coating on Ag substrate for magnet technologies. ZrO₂ coatings were produced on Ag tape substrate by using a reel-to-reel sol–gel technique. SEM inspection showed that ZrO₂ coatings had mosaic structures. ANSYS finite element software was used to calculate the temperature and stress distribution of the ZrO₂/Ag structure. The effect of coating thickness on residual stresses was also examined. The results obtained showed that thermal stresses in ZrO₂ coating and Ag substrate were considerably affected by the cooling time and coating thickness. It is concluded the thermal stresses increase with increase of film thickness.     

脉冲偏压对直流磁控溅射沉积MoN薄膜结构及性能的影响

MoN薄膜是一种具有潜在应用价值的薄膜材料,但对于其结构和性能的研究还较少。采用直流磁控溅射技术在304不锈钢基体表面沉积MoN薄膜,研究了脉冲偏压对MoN薄膜结构和性能的影响,并系统研究了MoN薄膜在不同摩擦条件下的摩擦磨损行为。采用X射线衍射仪和扫描电镜分析薄膜的晶相结构、晶粒尺寸、表面及断面形貌,采用HMV-2T显微硬度仪测试薄膜的显微硬度。采用UMT-TriboLab多功能摩擦磨损试验机评价薄膜的摩擦磨损性能,并用扫描电镜观察磨损表面,分析其磨损机制。结果表明：脉冲偏压显著影响直流磁控沉积的MoN薄膜的晶相结构、表面形貌、断面结构、硬度和摩擦磨损性能;随脉冲偏压的增大,MoN薄膜的膜厚、硬度都先增大后减小,而薄膜的磨损率却先减小后增大,其中-500 V脉冲偏压下沉积的MoN薄膜具有最高硬度为7731 N/mm²,以及最低的磨损率为5.8×10^-7 mm³/（N·m）。此外,MoN薄膜在不同载荷和转速的摩擦条件下表现出不同的摩擦学行为。     

Growth and characterization of Cr2N/CrN multilayer coatings

A series of monolithic and multilayer coatings of chromium nitride with various compositions and architectures were deposited at low temperatures (<200°C) on silicon substrates using ion-assisted reactive magnetron sputtering. All coatings had a total thickness in the 1.5±0.3 μm range. The multilayer coatings were designed such that their period and CrN fraction varied in the range 30–150 nm and 0.50–0.93, respectively. Real-time in situ ellipsometry was used to monitor and control the deposition process. The deposited coatings were characterized post-deposition using X-ray diffraction (XRD), Rutherford backscattering (RBS), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). The primary chromium nitride phases (Cr₂N and CrN) in the films were identified using XRD. The chemical composition of selected samples was determined from RBS and XPS measurements. The phase composition of the deposited layers was deduced from the analysis of the SE data. The mechanical properties of the coatings were evaluated using a nanoindenter. The measured hardness values were in excess of 20 GPa. The results of the different characterization and testing techniques were correlated and follow-up work on this project suggested.     

氮化物涂层对钛合金抗循环氧化性能的影响

用多弧离子镀技术在Ti6Al4V钛合金表面沉积Ti_0.5Al_0.5N/Ti_0.7Al_0.3N复合涂层和Ti_0.6Al_0.3Si_0.1N涂层,研究其在550℃~750℃下的抗循环氧化性能。结果表明,TiAlSiN涂层以及Ti_0.5Al_0.5N/Ti_0.7Al_0.3N复合涂层在550℃和650℃氧化后表面形成薄而连续的保护性富铝氧化膜,显著提高了Ti6Al4V的抗氧化性能。在750℃下,TiAlSiN涂层涂敷的Ti6Al4V依然保持着优异的抗循环氧化性能,而Ti_0.5Al_0.5N/Ti_0.7Al_0.3N复合涂层却不能为钛合金提供有效的防护。     

Al含量对TiAlN涂层结构及性能的影响

目的 系统研究Al含量对TiAlN涂层结构以及硬度、热稳定性、抗氧化性能和耐腐蚀性能的影响.方法 利用阴极弧蒸发技术,采用Ti、Ti50Al50、Ti40Al60和Ti33Al67靶材制备出4种Ti1–xAlxN涂层.分别利用能量色散X射线光谱仪(EDX)、X射线衍射仪(XRD)、扫描电镜(SEM)、纳米压痕仪、热重分...     

FeAl and Mo–Si–B intermetallic coatings prepared by thermal spraying

FeAl and Mo–Si–B intermetallic coatings for elevated temperature environmental resistance were prepared using high-velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques. For both coating types, the effect of coating parameters (spray particle velocity and temperature) on the microstructure and physical properties of the coatings was assessed. Fe–24Al (wt%) coatings were prepared using HVOF thermal spraying at spray particle velocities varying from 540 to 700 m/s. Mo–13.4Si–2.6B coatings were prepared using APS at particle velocities of 180 and 350 m/s. Residual stresses in the HVOF FeAl coatings were compressive, while stresses in the APS Mo–Si–B coatings were tensile. In both cases, residual stresses became more compressive with increasing spray particle velocity due to increased peening imparted by the spray particles. The hardness and elastic moduli of FeAl coatings also increased with increasing particle velocity. For Mo–Si–B coatings, plasma spraying at 180 m/s resulted in significant oxidation of the spray particles and conversion of the T1 phase into amorphous silica and -Mo. The T1 phase was retained after spraying at 350 m/s.     

Effect of Al additions in WC-(Cr1−xAlx)N coatings on the corrosion resistance of coated AISI D2 steel in a deaerated 3.5 wt.% NaCl solution

Multilayered WC-(Cr_1−xAl_x)N coatings were deposited on AISI D2 steel using cathodic arc ion plating (CAIP) process. Five kinds of WC-(Cr_1−xAl_x)N coatings were prepared: WC-Cr_0.6Al_0.4N, WC-Cr_0.57Al_0.43N, WC-Cr_0.53Al_0.47N, WC-Cr_0.48Al_0.52N and WC-Cr_0.45Al_0.55N. The Al concentration could be controlled by using evaporation source for Al targets and fixing the evaporation rate of the other metals (WC alloy and Cr). In this study, the corrosion behavior in deaerated 3.5 wt.% NaCl solution was investigated by electrochemical corrosion tests (potentiodynamic polarization test, galvanic corrosion test, electrochemical impedance spectroscopy (EIS)) and surface analyses (glow discharge optical emission spectroscopy, X-ray diffractometry, scratch adhesion test, scanning electron microscopy, electron probe micro-analyzer).

The results of potentiodynamic polarization test showed that the WC-Cr_0.48Al_0.52N coating with lower porosity exhibited the lower corrosion current density. The galvanic corrosion current between the coating and the substrate showed low values. In EIS measurements, the charge transfer resistance (R_ct) value of WC-Cr_0.48Al_0.52N coating only increased with the immersion time, when compared to the other coatings. It can be due to the corrosion products plugging the pores and increasing the pathway resistance.     

The wet corrosion of Mo and Mo‐Ti alloy thin film – Part IV: The effect of nitriding

A considerable number of detailed investigations have been carried out on the deposition and characterisation of molybdenum and molybdenum‐titanium‐nitride films by employing a variety of techniques. However, very little is currently known about the effect of composition (N₂/Ar flow rate) on the corrosion properties of MoN and MoTiN thin films for aggressive ambient conditions. In this work, the electrochemical and corrosion behaviour of MoN and MoTiN thin films, produced by Physical Vapour Deposition (PVD) with different N₂/Ar flow rates, has been investigated by Electrochemical Impedance Spectroscopy (EIS) in aerated alkaline chloride solution and compared with the behaviour of pure molybdenum in the same environment. Results obtained indicate that increasing nitrogen content in the film leads to a beneficial effect on the corrosion resistance, but results in decreased electrical conductivity of the film that may limit their application as back contact in photovoltaic modules.     

Residual stresses in titanium nitride thin films obtained with step variation of substrate bias voltage during deposition

In this work, a series of depositions of titanium nitride (TiN) films on M2 and D2 steel substrates were conducted in a Triode Magnetron Sputtering chamber. The temperature; gas flow and pressure were kept constant during each run. The substrate bias was either decreased or increased in a sequence of steps. Residual stress measurements were later conducted through the grazing X-ray diffraction method. Different incident angles were used in order to change the penetration depth and to obtain values of residual stress at different film depths. A model described by Dolle was adapted as an attempt to calculate the values of residual stress at each incident angle as a function of the value from each individual layer. Stress results indicated that the decrease in bias voltage during the deposition has produced compressive residual stress gradients through the film thickness. On the other hand, much less pronounced gradients were found in one of the films deposited with increasing bias voltage.     

Microgrinding of Nanostructured Material Coatings

This study is aimed at experimentally investigating the effect of microgrinding process on the surface finish, subsurface damage and residual stresses of thermally sprayed nanostructured WC/12Co (n-WC/12Co) and Al₂O₃/13TiO₂ (n-Al₂O₃/13TiO₂) coatings. The material removal mechanisms are discussed. Surface textures are measured with stylus profilometry, scanning electronic microscopy (SEM) and atomic force microscopy (AFM), and analyzed using conventional methods and scale-sensitive fractal analysis. Residual stresses are measured with glancing incident X-ray diffraction (GIXD) technique that is capable of providing the depth profiles of residual stresses. Investigated is also grinding damage to the coatings.     

Thermally-induced formation of hexagonal AlN in AlCrN hard coatings on sapphire: Orientation relationships and residual stresses

Cubic AlCrN coatings were epitaxially grown onto Al₂O₃(00.1) substrates by reactive magnetron sputtering at 500°C from Al/Cr targets with an atomic ratio of 70/30. The coatings were vacuum annealed at 1000°C for 2 hours in order to induce formation of wurtzite-type AlN. The as-deposited and annealed coatings were characterized using X-ray diffraction techniques. Pole figure measurements revealed orientation relationships of the cubic AlCrN phase with respect to the substrate. Residual stress characterization indicated compressive stresses of -1246 MPa in the as-deposited cubic AlCrN phase. After annealing, the residual stresses in the hexagonal wurtzite-type Al(Cr)N and the Al-depleted cubic Cr(Al)N phase are -132 and 346 MPa, respectively. The stress changes can be interpreted as a consequence of point defect recovery at temperatures above deposition temperature and Al(Cr)N formation in the annealed coating.     

X-ray diffraction measurement of residual stress and crystal orientation in Au/NiCr/Ta films prepared by plating

Au/NiCr/Ta films were prepared by plating and then annealed at 400 °C in Ar gas for an hour. The Au diffraction peak positions including incidence angles 0°, 15°, 30°, and 45° were measured by a glancing incidence X-ray diffraction (GIXRD) method. Residual stresses were then calculated using the sin²ψ method. The results indicate that the residual stress in the as-deposited Au/NiCr/Ta films was about 50 MPa, but was decreased down to − 5 MPa in average after samples annealing. The XRD analysis on crystal orientation shows that only the diffraction peaks of Au were found. There are no alloying phases in the plating Au film, and the interlayer of NiCr and Ta is too thin to be detected by the conventional XRD. The XRD also revealed that the films are highly textured with Au-(111) or a mixture of Au-(111) and Au-(200) orientation, and the (111)/(200) intensity ratio decreases after samples annealed.