Effect of Oxygen on the Self-formation of Carbonaceous Tribo-layer with Carbon Nitride Coatings under a Nitrogen Atmosphere

The ball-on-disk friction and wear tests of CN _X coatings (CN _X /CN _X ) were conducted under a nitrogen atmosphere with controlled relative humidity (RH) (3.4–40.0%RH) and oxygen concentration (100–21 × 10⁴ ppm) in this study. We found that the specific wear rate of CN _X coating on ball (W _b), which could give stable and low friction coefficient (<0.05), was below 3.0 × 10^?8 mm³/Nm. Average friction coefficients (µ _a) and W _b of CN _X /CN _X increased (µ _a: 0.02–0.33, W _b: 1.6 × 10^?8–2.4 × 10^?7 mm³/Nm) with increasing oxygen concentration (230–211,000 ppm) as well as RH (4.7–21.1%RH) under a nitrogen atmosphere. However, the W _b remained low value below 2.3 × 10^?8 mm³/Nm regardless of oxygen concentration (100–207,000 ppm) of a nitrogen atmosphere (3.4–3.9%RH) when CN _X -coated balls were slid against a hydrogenated CN _X (CN _X :H) coatings (CN _X /CN _X :H). Besides, the CN _X /CN _X :H achieved low and stable friction coefficient below 0.05 under a nitrogen atmosphere (10,000 ppmO₂) regardless of increasing RH up to 20%RH. Raman analysis indicated that the structure of carbon on the top surface of CN _X coating was changed from as-deposited CN _X coating in the case of low friction coefficient (<0.05). Furthermore, TOF-SIMS analysis provided the evidence that the carbon derived from CN _X -coated disk was considered to diffuse into the ball surface, and it mixed with the carbon derived from CN _X -coated ball on the wear scar, which formed the chemically bonded carbon tribo-layer. Low friction coefficient (<0.05) with CN _X coatings under a nitrogen atmosphere was achieved due to self-formation of the carbon tribo-layer.     

High temperature wear of cermet particle reinforced NiCrBSi hardfacings

The aim of the current study was to investigate erosive and impact/abrasive wear behaviour of TiC–NiMo and Cr₃C₂–Ni reinforced NiCrBSi hardfacings at temperatures up to 700 °C.Coatings were produced using plasma transferred arc cladding process. It was shown that the high temperature wear behaviour of TiC–NiMo and Cr₃C₂–Ni NiCrBSi hardfacings is influenced by oxidation. The formation of mechanical mixed layers and oxide films was observed for both investigated coatings. TiC–NiMo and Cr₃C₂–Ni reinforced hardfacings show high wear resistance at all testing temperatures for both impact/abrasion and erosion conditions.     

Triboengineering properties of ceramic oxide coatings under boundary friction against steel

The triboengineering properties of ceramic-oxide coatings are studied during boundary friction against steel 45. Ceramic-oxide coatings formed by microplasma oxidation can be used within a wide range of pressures (8–36 MPa) and sliding velocities (0.05–2 m/s) to ensure lower friction coefficient and wear rate of the materials in contact as compared to a steel-steel pair. The improved triboengineering characteristics of tribojoints with ceramic oxide are attributed to the formation of nanostructures (with 40–100 nm elements) and surface smoothing up to R _a = 5.1 nm. The nanostructure and frictional surface morphology of steel are found to be a result of oil I-40A modification by high-dispersed wear products of ceramics in the friction zone playing the role of a nanosize additive to the lubricating material.     

Quantitative proximate X-ray analysis of loose raw materials based on detection of diffraction and characteristic radiation

A method of rapid X-ray analysis is proposed. The content of the method is that the ratio I _d/I _i ^A is measured in two channels of a γ spectrometer, one of which is configured for the diffraction maximum of the determined phase (I _d) and the other measures the intensity of the spectral line of secondary element A (I _i ^A ), the atomic number of which is the same as that of the material of the X-ray tube anode. Results of the X-ray analysis of chromite and molybdenum are presented. The test rate was 7 min per test. The maximum deviation from the content of MoS₂ was 0.4% in standard specimens with concentrations of 24–29% and that of Fe and Cr₂O₃ was 0.3% for concentrations of 14–19%.     

Numerical and experimental study on the flow characteristics of abrasive slurry jet with polymer additives

Based on a refined mathematical model, the hydrodynamics of abrasive slurry jet (ASJ) was numerically investigated in consideration of the non-Newtonian rheological properties of the slurry. It is found that adding polymer has significant effects on the jet properties, such as axial velocity and abrasive volume fraction. The coherence length (L _c) is proposed to measure the initial region of jet, where external air acts insignificantly on the axial velocity magnitude and thus the averaged kinetic energy is large. In the ASJ flow field, L _c is increased after adding polymer additives, while reduced as the operating pressure (P ₀) goes up. The prediction to the L _c agrees well with the experimental results, with P ₀ ranging from 1 to 16 MPa. Accordingly, an empirical formula is presented to describe the relationship between L _c and P ₀. The distinct characteristics of ASJ with polymer additives together with the verified length model of coherence region provides a qualitative and quantitative basis for the optimization of ASJ machining process, for instance, improving cutting efficiency and precision.     

Adatom concentration distribution on an extrawide Si(111) terrace during sublimation

The formation of an adsorption layer on the Si(111) surface during sublimation at temperatures of 1000–1100 °C and subsequent quenching at T = 750 °C is studied by methods of in situ ultrahigh-vacuum reflection electron microscopy and ex situ atomic force microscopy. The adatom concentration distribution on an extrawide (~60 μm) atomically flat terrace is determined for the first time, and the diffusion length x_s = 31±2 μm at T = 1000 °C is obtained. The analysis of the temperature dependence of the equilibrium concentration of adatoms near a monatomic step allows pioneering measurements of the energy necessary for adatom detachment from the step and attachment to the terrace E _ad ≈ 0.68 eV. Based on these results, the energy parameters for some atomic processes on the Si(111) surface are estimated.     

Parametric optimization of CNC turning process for hybrid metal matrix composite

Machining of hybrid metal matrix composite is difficult as the particulates are abrasive in nature and they behave like a cutting edge during machining resulting in quick tool wear and induces vibration. An attempt was made in this experimental study to evaluate the machining characteristics of hybrid metal matrix composite, and a mathematical model was developed to predict the responses, namely surface finish, intensity of vibration and work-tool interface temperature for known cutting condition while machining was performed in computer numerical control lathe. Design of experiments approach was used to conduct the trials; response surface methodology was employed to formulate a mathematical model. The experimental study inferred that the vibration in V _x, V _y, and V _z were 41.59, 45.17, and 26.45 m/s², respectively, and surface finish R _a, R _q, and R _z were 1.76, 3.01, and 11.94 μm, respectively, with work-tool interface temperature ‘T’ of 51.74 °C for optimal machining parameters, say, cutting speed at 175 m/min, depth of cut at 0.25 mm and feed rate at 0.1 mm/rev during machining. Experimental results were in close conformity with response surface method overlay plot for responses.     

Cutting performance of Si<Subscript>3</Subscript>N<Subscript>4</Subscript>/TiC micro-nanocomposite ceramic tool in dry machining of hardened steel

A type of Si₃N₄/TiC micro-nanocomposite ceramic cutting tool material was fabricated using Si₃N₄ micro-matrix with Si₃N₄ and TiC nanoparticles. Cutting performance of the Si₃N₄/TiC ceramic cutting tool in dry cutting of hardened steel was investigated in comparison with a commercial Sialon insert. Hard turning experiments were carried out at three different cutting speeds, namely 97, 114, and 156 m/min. Feed rate (f) and depth of cut (a _p) were fixed at 0.1 mm/rev and 0.2 mm, respectively. Results showed that cutting temperature increased rapidly to nearly 1000 °C with increasing cutting speed. The two types of cutting tools featured similar wear behavior. However, the Si₃N₄/TiC micro-nanocomposite ceramic cutting tool exhibited better wear resistance than the Sialon tool. Morphologies of crater and flank wear were observed with a scanning electron microscope. Results indicated that wear variation of the two types of ceramic cutting tools differed in the same conditions. Wear of the Si₃N₄/TiC micro-nanocomposite ceramic cutting tool is mainly dominated by abrasion and adhesion, whereas that of the Sialon ceramic cutting tool is dominated by abrasion, adhesion, thermal shock cracking, and flaking.     

Effect of Grain Boundary on the Wear Behaviour of NiTi Shape Memory Alloys When <Emphasis Type="Italic">M</Emphasis><Subscript>f</Subscript> &lt; <Emphasis Type="Italic">T</Emphasis> &lt; <Emphasis Type="Italic">A</Emphasis><Subscript>f</Subscript>

Wear behaviour of NiTi SMA is closely corresponds to deformation mechanisms associated with different plastic strain accumulation process. Plastic strain accumulation is achieved by dislocation motion; however, grain boundary acts as a strong barrier. In this work, wear behaviour of single-crystalline and polycrystalline NiTi SMAs was studied to understand the effect of grain boundary on the plastic strain accumulation in the wear process. Wear tests were conducted at M_f < T < A_f, where phase boundary exists between martensitic and austenitic phases. Tests were conducted under ball-on-disc sliding wear mode, and alumina (Al₂O₃) counter-body was used. For single-crystalline NiTi SMA, transition wear occurred even when the applied load was relatively low (i.e., 100 mN). For polycrystalline NiTi SMA, with increasing applied load and wear cycles, the wear has shifted from near-zero wear stage to severe wear stage; no transition behaviour was observed. Significant differences in the wear process were discussed with respect to deformation mechanisms associated with dislocation motion in the single-crystalline and polycrystalline NiTi SMAs.     

Calculation of negative-pressure chip in suction-type internal chip removal system and analysis of influencing factors

Compacted graphite iron (CGI) is considered as the ideal material to make modern fuel-efficient diesel engine. Due to the vermicular or worm-like graphite distributed among the ferrite/pearlite matrix, CGI behaves better physical and mechanical properties in comparison with gray cast iron (GCI) and spherical graphite spheroidal cast iron (SGI). However, these good properties bring about the machining challenges. So it is important to appropriately select cutting parameters to machine this material with economy and efficiency. The present study investigated the influence of cutting parameters, such as cutting speed V, feed rate f, and exit angle Ψ, on workpiece material removal volume Q and cutting burr height on the entrance side H₁ and on the exit side H₂ during high-speed milling of CGI by the coated carbide tools_. On this basis, the relatively optimum high-speed cutting parameters were selected under the research condition. Cutting tool failure mechanism was also investigated with the aid of scanning electronic microscope (SEM) and energy-dispersive system (EDS) (SUPRA55, Germany) analysis. The results showed that Q, H₁, H₂, and the type of cutting burr on the exit side of the machined surface could be influenced by the cutting parameters. And the relatively optimum cutting parameters are V = 800 m/min, f = 0.25 mm/rev, and Ψ = 60°. Adhesive wear and thermal cracks which were perpendicular to the cutting edge were common wear mechanisms during the cutting process. However, with an increase in feed rate, mechanical cracks which were parallel to the cutting edge could be found on the flank face of the cutting tool.     

Spectroscopy of Single AlInAs Quantum Dots

A system of quantum dots based on Al _x In_1?xAs/Al _y Ga_1?yAs solid solutions is investigated. The use of Al _x In_1?xAs wide-gap solid solutions as the basis of quantum dots substantially extends the spectral emission range to the short-wavelength region, including the wavelength region near 770 nm, which is of interest for the development of aerospace systems of quantum cryptography. The optical characteristics of Al _x In_1?xAs single quantum dots grown by the Stranski–Krastanov mechanism were studied by cryogenic microphotoluminescence. The statistics of the emission of single quantum dot excitons was studied using a Hanbury Brown–Twiss interferometer. The pair photon correlation function indicates the sub-Poissonian nature of the emission statistics, which directly confirms the possibility of developing single-photon emitters based on Al _x In_1?xAs quantum dots. The fine structure of quantum dot exciton states was investigated at wavelengths near 770 nm. The splitting of the exciton states is found to be similar to the natural width of exciton lines, which is of great interest for the development of entangled photon pair emitters based on Al _x In_1?xAs quantum dots.     

Finite element analysis on axial-pushed incremental warm rolling process of spline shaft with 42CrMo steel and relevant improvement

In this paper, the influence of the configuration of the geometric structure of the machined surface on the course of the wear process of frictional pairs is discussed. Arrangement of traces of machining determined the level of surface structure isotropy. The characteristics of surface layers are discussed, with particular emphasis on the surface structure isotropy. The results of experimental investigations carried out on the specially designed and made setup are presented. As the measures of the wear process, the following quantities were determined: the mass decrement of samples and changes of the surface roughness parameters, root mean square (RMS) of profile R _q and reduced peak height of profile R _pk . The results of experimental investigations were registered for structures with different levels of isotropy and, thus, traces of machining. The investigations confirm the influence of the tested factors on the intensity of the wear process.     

Analysis on annealing-induced stress of blind-via TSV using FEM

Copper-filled through silicon via (TSV) is a promising material owing to its application in high-density three-dimensional (3D) packaging. However, in TSV manufacturing, thermo-mechanical stress is induced during the annealing process, often causing reliability issues. In this paper, the finite element method is employed to investigate the impacts of via shape and SiO₂ liner uniformity on the thermo-mechanical properties of copper- filled blind-via TSV after annealing. Top interface stress analysis on the TSV structure shows that the curvature of via openings releases stress concentration that leads to ~60 MPa decrease of normal stresses, σ_xx and σ_yy, in copper and ~70 MPa decrease of σ_xx in silicon. Meanwhile, the vertical interface analysis shows that annealing-induced stress at the SiO₂/Si interface depends heavily on SiO₂ uniformity. By increasing the thickness of SiO₂ linear, the stress at the vertical interface can be significantly reduced. Thus, process optimization to reduce the annealing-induced stress becomes feasible. The results of this study help us gain a better understanding of the thermo-mechanical behavior of the annealed TSV in 3D packaging.     

Calculating the wear resistance of metals in frictional pairs 3. Calculating the wear rate of steel in roller pairs with rolling friction and slip

On the hypothesis that slipping friction has the primary influence on the wear of steel in a rolling frictional pair with slip, the dimensionless wear rate I of wheel steel in the driven roller and the dimensional wear rate W (expressed in terms of I) are calculated. Satisfactory agreement of the theoretical and experimental wear rates is observed in the regions of weak, pronounced, and catastrophic wear.     

Study of trajectory and experiment on steel polishing with elastic polishing wheel device

Since the curvature of free-form surfaces are variable, it is difficult to guarantee the quality of the surface polished with traditional polishing technology. The chief aim of this paper is to investigate the features of an original elastic polishing wheel device. The polishing trajectory of the elastic polishing wheel was simulated to study the relationship between the uniformity of a kind of polishing trajectory and the ratio of rotational speed “i” which is the ratio of the velocity of the rotation and the revolution. Orthogonal experiment was carried out to explore the effect of various factors (rotational ratio, press amount h, speed of rotation, and granularity of abrasive grains) on surface roughness polished. The writer has come to the conclusion that i has an influence on the uniformity of polishing trajectory. The polishing coefficient of variation “CV” of i?=?10.645751 is 32% lower than i?=?10. Increasing the number of digits after the decimal point of i, the polishing track performs more uniform and densely. The experimental tests show that the influence of rotational ratio, press amount h, speed of rotation, and granularity of abrasive grains on surface roughness polished decreases progressively.     

Microstructure and tribological properties of laser clad γ/Cr7C3/TiC composite coatings on γ-TiAl intermetallic alloy

In order to improve the wear resistance of the γ-TiAl intermetallic alloy, microstructure, room- and high-temperature (600 °C) wear behaviors of laser clad γ/Cr₇C₃/TiC composite coatings with different constitution of NiCr–Cr₃C₂ precursor-mixed powders have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrometer (EDS), block-on-ring (room-temperature) and pin-on-disk (high-temperature) wear tests. The responding wear mechanisms are discussed in detail. Results show that microstructures of the laser clad composite coatings have non-equilibrium solidified microstructures consisting of primary hard Cr₇C₃ and TiC carbides and the inter-primary γ/Cr₇C₃ eutectic matrix, about three to five times higher average microhardness compared with the TiAl alloy substrate. Higher wear resistance than the original TiAl alloy is achieved in the clad composite coatings under dry sliding wear conditions, which is closely related to the formation of non-equilibrium solidified reinforced Cr₇C₃ and TiC carbides and the positive contribution of the relatively ductile and tough γ/Cr₇C₃ eutectics matrix and their stability under high-temperature exposure.     

Vibration response analysis caused by rubbing between rotating blade and casing

Two types of blade-tip rubbing due to the static misalignment of the bladed-disk center and casing center and casing deformation are simulated. By applying aerodynamic load in the blade lateral/flexural direction, vibration responses due to blade-casing rubbing are analyzed under the run-up process with constant angular acceleration and the steady-state process at 10000 rev/min. The effects of some parameters, such as the static misalignment e _c, casing stiffness k _c and casing deformation n _p, on the system vibration responses are also illustrated by spectrum cascades, time-domain waveforms of displacement, normal rubbing forces, amplitude spectra and the impulse P in a single blade-casing rubbing period. The results show that blade-tip rubbing will cause amplitude amplification and harmonic resonance phenomena when the multiple frequencies (nf _r) of rotational frequency (f _r) coincide with the first three flexural dynamic frequencies of the blade (f _n1, f _n2 and f _n3). For example, the displacement amplitudes at 3f _r, 14f _r and 38f _r are large and the vibration is dominant near f _n1. In addition, the casing deformation mainly excites the dominant Blade passing frequency (BPF), which is related to the casing deformation coefficient n _p. By comparing these impulse values, for the selected parameters in this paper, the casing stiffness has a greater effect on impulse than the static misalignment and casing deformation coefficient. The impulse shows a linear increase trend with the increasing static misalignment, and it decreases under the large n _p because the contact time decreases with the increase of n _p.     

Method for determining critical pressure in assembling hybrid MCT focal plane arrays

A simple method is proposed for determining the critical pressure that does not destroy Cd _x Hg_1?x Te diodes in hybrid assembling. The method allows obtaining a set of data that reliably define the critical parameter (the value of force) of the flip-chip hybrid FPA process. The method was tested on Cd _x Hg_1?x Te samples (x = 0.21). It is found that the abrupt change in the electrophysical properties of the material occurs when the diameter of indium bumps increases 2 times and more during compression at a pressure of about 3 kg/mm². The obtained gage load/bump deformation dependences show that this pressure corresponds to the beginning of the region of indium strengthening on the deformation curve.     

Multi-color space threshold segmentation and self-learning <Emphasis Type="Italic">k</Emphasis>-NN algorithm for surge test EUT status identification

The identification of targets varies in different surge tests. A multi-color space threshold segmentation and self-learning k-nearest neighbor algorithm (k-NN) for equipment under test status identification was proposed after using feature matching to identify equipment status had to train new patterns every time before testing. First, color space (L*a*b*, hue saturation lightness (HSL), hue saturation value (HSV)) to segment was selected according to the high luminance points ratio and white luminance points ratio of the image. Second, the unknown class sample S _r was classified by the k-NN algorithm with training set T _z according to the feature vector, which was formed from number of pixels, eccentricity ratio, compactness ratio, and Euler’s numbers. Last, while the classification confidence coefficient equaled k, made S _r as one sample of pre-training set T _z ′. The training set T _z increased to T _z+1 by T _z ′ if T _z ′ was saturated. In nine series of illuminant, indicator light, screen, and disturbances samples (a total of 21600 frames), the algorithm had a 98.65%identification accuracy, also selected five groups of samples to enlarge the training set from T ₀ to T ₅ by itself.     

Nonparametric estimation of a probability density function and its derivatives. <Emphasis Type="Italic">C</Emphasis>-approach

Nonparametric (kernel) estimation of a probability density function f(x) for a sample of finite size is considered using the C-approach. The smoothness parameter β of the estimated probability density is introduced. For the case β > 2, it is shown that the convergence of the density estimate f _n (x) to the function f(x) can be improved by using alternating-sign weight functions (higher-order weight functions). Estimation of the derivatives of a function is briefly considered using the same approach.