Tribological performance evaluation of (1 1 1) preferred oriented TiN duplex coatings

The duplex surface coating of hot work tool steel, which comprises nitriding of a substrate and coating of a TiN layer, has been the subject of a series of studies as a potential surface modification for tools and machine parts. Through sliding experiment against an aluminum alloy without lubrication, it was shown on a wear map that there are two domains depending on sliding conditions: the wear domain and the transfer domain. In this study, focusing on the improvement in the tribological properties of the duplex coating in terms of the wear domain, the effects of film characteristics on film resistance to erosion wear and film life were investigated. Two kinds of duplex coatings with different film characteristics were prepared by hollow cathode discharge ion plating: a newly developed TiN film with a strong (1 1 1) orientation and an ordinary TiN film with (1 1 1) and (2 0 0) orientations. The erosion wear rate of duplex coating was evaluated by a micro slurry jet erosion test. Film life was evaluated by a sliding test against an aluminum alloy as in previous experiments. It was revealed that the duplex coating with the newly developed TiN film (N-coating) shows higher erosion resistance than previously reported duplex coating (C-coating). From the sliding test, it was also revealed that the N-coating whose XRD intensity ratio of (1 1 1) to (2 0 0) is over 100 shows a wear mode with only chipping, with no scratching, which shortens film life. The film life of N-coating increases about twice as long as C-coating, which has shown higher performance than a conventional duplex coating. Possible mechanisms of the improvement in the tribological properties with N-coating are discussed.     

Sliding wear behaviour of ZrN and (Zr, 12 wt% Hf)N coatings

In the present study, the sliding wear resistances of ZrN and (Zr, 12 wt% Hf)N coatings deposited on a hardened AISI D2 tool steel by arc-physical vapor deposition (PVD) technique were examined by a ball-on-disc wear tester. Alloying of ZrN coating with 12 wt% Hf did not change the hardness significantly, but achieved an improvement on adhesion strength and dry sliding wear resistance against steel (AISI 52100-55HRC) and Al₂O₃ balls.     

Cavitation erosion-corrosion behaviour of CrMnB stainless overlay and 0Cr13Ni5Mo stainless steel in 0.5 M NaCl and 0.5 M HCL solutions

The cavitation erosion-corrosion behaviour of CrMnB overlay was investigated in comparison with 0Cr13Ni5Mo stainless steel in 0.5 M NaCl and 0.5 M HCl solutions by using a magnetostrictive-induced cavitation facility. The micrographs of damaged surfaces were observed by scanning electron microscope (SEM), and the polarization curves were measured under quiescent and cavitating condition. The results showed that the cavitation erosion-corrosion resistance of CrMnB overlay was 14 times higher than that of 0Cr13Ni5Mo steel in NaCl solution, but, the cavitation erosion-corrosion resistance was 5.7 times lower in HCl solution. For CrMnB overlay in NaCl solution, the excellent cavitation erosion-corrosion resistance could be attributed to strain-induced martensite transformation and its “skeleton” structure of borides. For CrMnB overlay in HCl solution, the electrochemical dissolution promoted the borides to drop out. The martensite transformation was retarded by cushion effect of H₂ gas. Material removal in massive chunks (independent on the microstructural features) was accelerated by connection of cavitation cracks, which was enhanced by hydrogen embrittlement. These results suggested that developing steels with high martensite transformability and boride strengthening is an important method to design coatings or steels used in neutral cavitation environments, but which is not suitable for acidic environments.     

Sliding wear behaviour of aluminum syntactic foam: A comparison with Al-10 wt% SiC composites

The sliding wear behaviour of cenosphere-filled aluminum syntactic foam (ASF) has been studied in comparison with that of 10 wt% SiC particle reinforced aluminum matrix composite (AMC) at a load of 3 kg and varying sliding speeds under dry and lubricated conditions using a pin-on disc test apparatus. The tribological responses such as the wear rate, the coefficient of friction and the frictional heating were investigated. The wear surfaces and subsurfaces were studied for understanding the wear mechanism. It was noted that the coefficient of friction, the wear rate, and the temperature rise for ASF are less than that for AMC in both dry and lubricated conditions. The craters (vis-à-vis exposed cenospheres) play an important role in the wear mechanism for ASF.     

红外探测器件在低温背景下的探测率测试

建立了红外探测器件低温背景探测率测试系统,实验研究了红外探测器件在低温背景下的探测特性,用于支持红外探测低温光学系统的合理设计.首先,介绍并分析了红外探测系统的噪声和响应特性,建立了低温光学系统设计与红外探测器件在低温背景下探测性能之间的关系;在热真空环境下搭建了基于变温面源黑体的低温背景探测率测试系统.然后,针对某红外器件在低温背景下的探测率进行了实验测量.最后,通过计算得到了低温背景下极限积分时间及探测特性相对于常温背景下的一般变化规律.实验结果表明:低温背景下极限积分时间及探测率均比常温背景下提高近20倍,提出的测试技术可为低温光学系统的指标设计提供依据与参考.     

复合材料低速冲击损伤超声红外热波检测能力评估

为评估超声红外热成像对复合材料低速冲击损伤的检测能力,提出了评估流程和评估标准。设计并制作了复合材料层合板,分别采用超声红外热成像和超声C扫描两种方法对不同冲击能量下的冲击损伤进行了检测研究,以超声C扫描结果作为参照,对比分析了超声红外热成像的检测结果并对损伤大小进行了定量识别。结果表明:超声红外热成像不仅能够对冲击损伤进行准确的定位,还能有效地检测出冲击引起的纤维断裂、基体开裂和分层等具体的损伤形式,检测速度快,非常适合用于在线检测;与超声C扫描相比,超声热成像方法对冲击损伤大小的识别误差小于6%,检测精度较高,满足检测要求。     

Wear and immersion corrosion of Ni–P electrodeposit in NaCl solution

This paper presents an experimental study on the block-on-cylinder wear behavior of an electroplated Ni–P coating immersed in 5% NaCl solution at different temperatures and polarization potentials. The simply immersion corrosion without normal load was performed first, and then the corrosion effect on the wear behavior including friction coefficient, surface roughness and weight loss were discussed. It is found that the morphology nature of the corrosion film has crucial effect on the wear performance of the coating. Moreover, the bath temperature and the polarization potential greatly influence the formation of the corrosion film.     

Analysis of pressure distribution for the various gas flow vacuum system in the range from 1 Pa to 133 Pa

The measurement and control of gas flow are critical in many manufacturing processes. Semiconductor manufacturers, in particular, require a number of different process gases for etching, deposition, oxidation, doping and inerting applications. In many of these, as well as other industrial and research processes including measurement of partial pressures with residual gas analyzers (RGAs), calibration of vacuum gauges, and conductance of a conductance-reducer , accurate measurement and stability of the gas pressure within the reaction vacuum chamber is essential. In the present work, pressure distribution in the chamber of a newly developed flow control system was investigated for three gases (Ar, N₂, and He) range from 1 Pa to 133 Pa. For all the gases, the relative deviations in pressure distribution near the gas inlet and outlet were in the range of −1.3% and 1.2% respectively.     

Kinematic calibration analysis of 3SPS + 1PS bionic parallel test platform for hip joint simulator

As the key component of the parallel hip joint simulator, 3SPS + 1PS bionic parallel test platform owns four degrees of freedom including three rotations and one translation. When the moving platform stays at a given translation position, the parallel manipulator can represent three-dimensional rotating gait motions of the hip joint for the purpose of evaluating the friction characteristics of biological materials. Because of the manufacturing and assembling errors, the actual structure parameters of the parallel manipulator are not more accurate than the theoretical values and its reduced simulation accuracy will bring the uncertain evaluation. So in order to improve the precisions in the design, manufacture and assembly of the parallel manipulator, it is necessary to calibrate the kinematic parameters. Considering the structural characteristics of the parallel manipulator, its error model and the corresponding compensation method are established based on the complete differential-coefficient theory. According to the constant values of two orientation angles, the orientation residual matrix is constructed by adopting the incomplete measurement method and the forward kinematics functions, so its cost function can be defined. The iterative algorithm based on the least square method is applied to identify the structure parameters and obtain their optimal solutions, and then the actual kinematic calibration process is simulated by numerical method. The simulation results show that the comprehensive orientation error after calibration is greatly decreased, and the effectiveness of the calibration method is validated.     

Formation of large ordered domains in benzenethiol self-assembled monolayers on Au(1 1 1) observed by scanning tunneling microscopy

Benzenethiol (BT) self-assembled monolayers (SAMs) on Au(1 1 1) were prepared as a function of solution temperature after immersion in a 1 mM ethanol solution for 1 day. The surface structures of BT SAMs were examined by means of scanning tunneling microscopy (STM). Although BT molecules usually form disordered SAMs containing the Au adatom islands at room temperature, we found that they formed two-dimensional ordered SAMs containing a large size domain at a high solution temperature of 50 or 75 °C. High-resolution STM imaging revealed that BT SAMs on Au(1 1 1) formed at 50 °C have a (2×3√2)R23° packing structure. From our STM study, we revealed that two-dimensional ordered BT SAMs on Au(1 1 1) can be obtained by changing the solution temperature.     

Evaluation of actual sensitivity limit in a 10 N·m dead weight torque standard machine and stability of a new 1 N·m torque transducer

A 10 N·m dead weight torque standard machine (10-N·m-DWTSM) has been under development at NMIJ/AIST since 2006 to expand the range of the torque standard. Estimation of the sensitivity limit of the fulcrum is one of the most important issues to realize a precise reference torque of small capacity by using a dead weight torque standard machine. In this study, a torque transducer was installed on the 10-N·m-DWTSM in order to keep the moment-arm on the horizontal line (balancing). The sensitivity limit of the fulcrum under real calibration conditions was estimated by reading the change in the output from the torque measuring device (TMD: the torque transducer with a cable and an indicating device) when small weights were loaded or unloaded. The small weights used in the experiment were 0.5 mg, 1 mg, 10 mg, and 100 mg. Equivalent radial loads from 0.1 N·m to 10 N·m were imposed on the fulcrum during the sensitivity measurement.     

A novel approach for realization of primary vibration calibration standard by homodyne laser interferometer in frequency range of 0.1 Hz to 20 kHz

The paper discusses the primary vibration calibration standard of NPL, India capable of calibrating the reference accelerometers in frequency range from 0.1 Hz to 20 kHz as per ISO 16063-11. The excitation subsystem produces constant vibration at a specified amplitude and frequency, while the measurement system uses NI interface for measuring the quadrature output. The acceleration level and voltage level at the calibration frequency f is determined by applying a Discrete Fourier Transform to the voltage and displacement signals, and then examining the spectral component at frequency f. A PC-based data acquisition system acquires the accelerometer voltage signal and analog quadrature interferometer photodetector signal pair as well as a digital quadrature pair whereby the software processes the demodulated photodetector signals to reconstruct the armature displacement. The validation of the calibration results for standard reference accelerometers with manufacturer results and uncertainty in calibration in entire frequency range 0.1 Hz to 20 kHz is reported in the present work.     

电化学阻抗谱研究Zn对用于阴极保护的Al-Zn合金在3% NaCl溶液中溶解行为的影响

采用电化学阻抗谱(EIS)研究了Al-Zn合金在不同极化电位下, 3% NaCl溶液中的溶解行为, 提出了Al-Zn合金在该条件下的活化反应模型及机理. 该活化反应中产生3个中间产物: Zn+ad、 Zn2+ad和Al+ad, 其中只有Zn+ad可以活化Al-Zn合金. 大部分Zn+ad由β相反应产生, Zn含量2.3%-3.8%wt的Al-Zn合金可以快速溶解. 具有心形EIS的Al-Zn合金在该溶液中处于活化状态, 因此采用EIS可以区分Al-Zn合金的活化状态.     

Quantitative characterization of chitosan in the skin by Fourier‐transform infrared spectroscopic imaging and ninhydrin assay: application in transdermal sciences

The chitosan has been used as the primary excipient in transdermal particulate dosage form design. Its distribution pattern across the epidermis and dermis is not easily accessible through chemical assay and limited to radiolabelled molecules via quantitative autoradiography. This study explored Fourier‐transform infrared spectroscopy imaging technique with built‐in microscope as the means to examine chitosan molecular distribution over epidermis and dermis with the aid of histology operation. Fourier‐transform infrared spectroscopy skin imaging was conducted using chitosan of varying molecular weights, deacetylation degrees, particle sizes and zeta potentials, obtained via microwave ligation of polymer chains at solution state. Both skin permeation and retention characteristics of chitosan increased with the use of smaller chitosan molecules with reduced acetyl content and size, and increased positive charge density. The ratio of epidermal to dermal chitosan content decreased with the use of these chitosan molecules as their accumulation in dermis (3.90% to 18.22%) was raised to a greater extent than epidermis (0.62% to 1.92%). A larger dermal chitosan accumulation nonetheless did not promote the transdermal polymer passage more than the epidermal chitosan. A small increase in epidermal chitosan content apparently could fluidize the stratum corneum and was more essential to dictate molecular permeation into dermis and systemic circulation. The histology technique aided Fourier‐transform infrared spectroscopy imaging approach introduces a new dimension to the mechanistic aspect of chitosan in transdermal delivery.     

A study of the effects of non-isothermal source conditions on the transfer of radiance temperatures in the temperature-wavelength domain from 180 to 30 000 μm K

The calibration of infrared pyrometers against a commercially available cylindroconical black-body system, operating in the range from 900 to 2900 K, forms the basis for the study presented in this paper.

The main features of the black-body system, in use at VSL, are briefly described. In practice, uniformity in temperature is difficult to achieve, especially at very high temperatures. For this reason, the effect of a non-uniform temperature distribution on the calibration accuracy was studied by model calculations, varying the relative temperature difference ΔT/T_b along the cylindrical wall of the cavity with respect to its bottom temperature T_b up to a maximum of 5%. Spectral emissivities = (λ, T_b) are calculated for a cylindro-conical geometry that approximates the real system. For some specific cases the effects for actually measured temperature distributions are also evaluated.

It is demonstrated that when transferring radiance temperatures from a lower wavelength (λ_s 0.6 μm), characterising the reference pyrometer, to the higher effective wavelength of the (spectral) infrared pyrometer to be calibrated (λ_x 6 μm), compensation of errors leads in general to a considerable reduction of the overall error, arising when neglecting the effect of departures from temperature uniformity, the reduction being more pronounced the higher the temperature.     

Evaluation of moment arm length and fulcrum sensitivity limit in a 10 N·m dead weight torque standard machine

Many torque tools, such as torque wrenches and torque screwdrivers, as well as torque measuring devices (TMDs) with a rated capacity of less than 5 N·m are being widely used in industry. Thus, a small-rated-capacity torque standard has to be established as soon as possible. A 10 N·m dead weight torque standard machine (10 N·m DWTSM) has been under development since 2006 at the National Metrology Institute of Japan (NMIJ), part of the National Institute of Advanced Industrial Science and Technology (AIST). Characteristically, the main parts of the moment arm are made of low thermal-expansion alloy (Super INVAR), and an aerostatic bearing is employed as the fulcrum supporting the moment arm to minimize rotational friction. The moment arm was evaluated with regard to the coefficient of thermal expansion (CTE), the lengths measured by a 3D coordinate measurement machine (CMM), and temperature correction realized by measuring the moment arm temperature. The sensitivity limit of the fulcrum in the 10 N·m DWTSM was also estimated. As a result, the apparent overall CTE of the moment arm was 1.06 × 10⁻⁶ K⁻¹, and the expanded uncertainty was 2.24 × 10⁻⁹ K⁻¹ (k = 2). The results of the CMM measurement were a right-hand side length of 510.2773 mm and a left-hand side length of 510.2657 mm, with a relative expanded uncertainty of 4.0 × 10⁻⁵ (k = 2). The moment arm temperature increased by approximately 0.6 K during the ordinary calibration process. The corresponding change in the lengths of the moment arm was estimated to be approximately 0.3 μm, which is considered to be sufficiently small compared with the expanded uncertainty of the lengths of the moment arm. The fulcrum of the 10 N·m DWTSM was found to have sufficient sensitivity under three conditions: without the weight loading components, with the weight loading components, and with loaded weights. In particular, the fulcrum had sufficient sensitivity of at least 0.5 mg when weights of 100 g were loaded on both 5th stages in the weight loading components to generate a radial load equivalent to 1 N·m.     

Bilateral comparisons of measurement capabilities for the calibration of low nominal capacity torque measuring devices between NMIJ and PTB in the range from 0.1 N m to 10 N m using different procedures

Bilateral comparisons of the calibration of low nominal capacity torque measuring devices (TMDs) were conducted between NMIJ and PTB for the first time. A 10 N m deadweight torque standard machine (TSM) newly developed at NMIJ was compared with PTB’s two TSMs with nominal capacities of 1 N m and 1 kN m, in the range from 0.1 N m to 10 N m. The transfer measurement devices used had nominal capacities of 1 N m and 10 N m. The comparisons were made using two calibration procedures: one based on the CCM.T-K2 Key Comparison procedure and the other according to the daily calibration procedure adopted at each institute. As a result, the torque realized by the TSM at NMIJ was shown to be equivalent to that realized by the two TSMs at PTB. In addition, it was confirmed that the daily calibration procedures of both institutes yielded consistent results in the calibration of low nominal capacity TMDs.     

Microstructural evolution of Cu-1 at% Ti alloy aged in a hydrogen atmosphere and its relation with the electrical conductivity

Copper alloys with titanium additions between 1 and 6 at% Ti emerge currently as attractive conductive materials for electrical and electronic commercial products, since they exhibit superior mechanical and electrical properties. However, their electrical conductivity is reduced owing to the residual amount of Ti solutes in the Cu solid solution (Cu_ss) phase. Since Cu shows only poor reactivity with hydrogen (H), while Ti exhibits high affinity to it, we were inspired by the idea that hydrogenation of Cu–Ti alloys would influence their microstructure, resulting in a significant change of their properties. In this contribution, the influence of aging under a deuterium (D₂) atmosphere of Cu-1 at% Ti alloys on their microstructure is investigated to explore the effects on the electrical conductivity. The specimens were investigated by means of transmission electron microscopy (TEM), field ion microscopy (FIM), computer-aided field ion image tomography (cFIIT), and atom probe tomography (APT).     

Stable and super‐low friction of amorphous carbon nitride coatings in nitrogen gas by using two‐step ball‐on‐disk friction test

Effect of running‐in process on friction behaviour of carbon nitride (CNx) coating in N₂ gas stream was investigated with a newly introduced two‐step ball‐on‐disk friction test, where the rubbed Si₃N₄ ball in the pre‐sliding (step 1) was replaced by a new CNx‐coated Si₃N₄ ball in the subsequent sliding stage under N₂ gas (step 2). The two‐step friction test is clarified to be a simple but effective technique for obtaining contact material combination of self‐mated CNx coatings and for achieving stable and low frictions of CNx coatings. Friction coefficients of CNx/CNx in N₂ gas stream decrease greatly from 0.07 without pre‐sliding to less than 0.025 in two‐step friction tests. The minimum friction coefficient of 0.004 was obtained by introducing 500 cycles of pre‐sliding in ambient air. These stable and low frictions are attributed to the generation of self‐mated CNx coatings and the formation of a lubricious layer on the disk surface. Copyright © 2014 John Wiley & Sons, Ltd.     

Sliding wear behaviour of Ca α-sialon ceramics at 600 °C in air

As an extension of a previous investigation on the wear behaviour of Ca α-sialon ceramics of differing microstructures at room temperature, wear testing was conducted at 600 °C in air to explore the effects of microstructure, contact pressure and sliding speed on the wear behaviour. Under all loading conditions from 1 MPa to 1 GPa, a constant high friction coefficient was observed and a severe wear process was dominant, in which the sliding contact induced cracks were observed in different microstructures. Wear particles were generated along the wear track, but no tribofilm was detected. Increasing the sliding speed from 10 to 23 cm/s was found to significantly increase wear rate. However, variations in microstructure had little impact. That is, large elongated-grained α-sialon exhibited only a slightly lower wear rate than fine equiaxed-grained α-sialon.