Boron Coatings Research Articles

Properties of Ni-B/B Composite Coatings Produced by the Electroless Method under Semi-Technical Line Conditions

Composite coatings have been successfully fabricated at the laboratory scale in many research centers around the world; however, it is still a major challenge to transfer the positive results of the work to the industrial scale. This paper presents the technology for the production of Ni-B and Ni-B/B composite coatings on a pilot experimental semi-technical line by chemical reduction. A process scheme for the fabrication of Ni-B layers and composite coatings with a nickel–boron matrix and a dispersive phase in the form of boron nanoparticles was developed. All stages of the fabrication process were described in detail. The dispersion phase of the boron particles was characterized, and the performance properties of the Ni-B and Ni-B/B composite coatings produced on a pilot electroplating line were studied. The structure and morphology of the Ni-B/B composite coatings were characterized for comparison with nickel–boron coatings. Their mechanical and tribological properties and adhesion to the substrate were studied. The influence of the dispersion phase of boron particles on the structure and functional properties of the composite coatings was evaluated. In order to improve the performance of the fabricated coatings, a heating process at 400 °C was carried out, and the performance of Ni-B and composite Ni-B/B coatings was studied after the heat treatment operation.

DEPOSITION OF PURE BORON COATINGS BY MAGNETRON SPUTTERING AND INVESTIGATION OF THEIR PROPERTIES

Pure boron coatings have been deposited on stainless-steel substrates using a planar magnetron with a thermally insulated target of pure crystalline boron in a direct current discharge of up to 50 mA in an argon atmosphere. The magnetron was designed to be used as a component in an electron-ion-plasma test bench for in situ monitoring of boron deposition growth using synchrotron radiation from the VEPP-3 electron storage ring at the Budker Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences. Using this magnetron, we have fabricated boron films with thickness up to 1.5 μm and studied their surface morphology, mechanical properties, and coating composition.

Development of Boron Coatings for antenna protection limiters in the WEST Tokamak

During the upgrade of Tore Supra to transform the machine into a fully metallic plasma facing environment (WEST), the Antennae Protection Limiters (APL), originally made in CFC, have been covered with a Tungsten coating with a Molybdenum interlayer (W/Mo/CFC).However, due to the aging of the W/Mo/CFC coating, the APL have been redesigned and future antenna limiters will be made of copper alloy (CuCrZr) heat sink structure with a thick boron (B) coating to reduce remaining W impurity levels during plasma operations and address the blistering issues seen in previous coatings.Among all the techniques able to realise B coating, Plasma Spray is the most appropriate technique owing to its simplicity, low cost and ability to deposit thick boron coatings on complex geometries.Various boron coatings with thicknesses up to 900 µm were produced, characterized and their thermal behavior have been assessed using a specific laser heating program and a conventional electron/ion beam facility. This paper provides an overview of the R&D activities on boron coating developments and the related validation programs showing that the thermal conductivity of deposited films is drastically reduced compared to bulk boron, preventing use without additional coating optimization.

Investigation of the Properties of Boron Coatings Obtained by Electron-Beam Evaporation of Pure Boron

Investigation of the Properties of Boron Coatings Obtained by Electron-Beam Evaporation of Pure Boron

Influences of La3+ Concentrations on Properties of Electroless Nickel–Phosphorus–Boron Coatings

Influences of La3+ Concentrations on Properties of Electroless Nickel–Phosphorus–Boron Coatings

Effect of low nitrogen concentration on reactive RF sputtering of boron

Monolayer boron and B/Mo/B/Mo coatings were prepared by reactive magnetron sputtering in the N2/Ar atmosphere with different RF powers, and the effect of the N2:Ar flow ratio was studied. It was found that as the N2:Ar flow ratio increased, the deposition rate of boron coatings exhibited three different stages of variation due to different mechanisms. The variation of deposition rate with increasing N2:Ar flow ratio was consistent for different RF powers. Berg's model explained experimental findings. XPS revealed that the coatings contained more than 86 % boron nitride (BN) when the N2 flow ratio was above 0.053 at 300W RF power. An optimal ratio exists that maximizes the boron deposition rate and produces a nearly pure boron nitride coating without target poisoning.

Investigation of Ni-Cu-B and Ni-Cu-Sn-B coatings developed by electroless method

Due to their remarkable mechanical properties and tribological behaviour which is equivalent the hard chrome coating, electroless Nickel–Boron coatings have been employed in a variety of industries. With the advent of emerging and challenging applications, there has been a need to develop newer variants of the novel Ni-B binary variant. The present work therefore investigates Ni-B-Cu coatings in a quest to achieve higher wear and corrosion resistance. A stabilizer free bath and tin chloride stabilized bath was formulated for the same to remove the harmful lead nitrate from the coating formulation. The concentration of copper sulphate was varied from 0.3 to 0.7 g/L in both the bath formulations. Based on the mass gain of the specimens, coatings obtained from 0.6 g/L copper sulphate was further investigated. The surface morphology of as-plated samples was observed which shows nodular structure and the growth was different compared to lead stabilized baths. The constant load and progressive scratch test were done to evaluate scratch hardness and coating failure respectively.

Deposition and process parameter optimization of electroless Ni-B coating from a stabilizer free bath to achieve enhanced microhardness, scratch-hardness and adhesion using taguchi’s methodology

Electroless nickel boron coatings have wide industrial usage. However, they are generally obtained from a lead-stabilized bath. The present work investigates and optimizes the scratch-hardness and microhardness obtained from stabilizer-free electroless nickel boron bath in a quest to eliminate lead nitrate/heavy metals, which are potentially toxic. The bath temperature, heat treatment temperature, and duration were varied at three levels. Enhanced scratch-hardness (12.581 GPa) was obtained at 85 °C bath temperature and heat treatment at 350 °C for 1 h. At the same time, the highest microhardness (886.17 HV100) was obtained at a parametric combination of 95 °C bath temperature and heat treatment at 450 °C for 1 h. Multi-objective optimization was carried out using grey relational analysis. The parametric combination predicted in multi-objective optimization was 85 °C bath temperature and heat treatment at 350 °C for 1 h where the microhardness was 846.34 HV100. Furthermore, an analysis of variance was also carried out to investigate the importance of the factors in controlling scratch-hardness and microhardness. The highest contribution was observed from heat treatment duration. Further investigation of the optimized coating was done by the progressive scratch test, which recorded that the first critical load of failure improved compared to non-heat treated electroless Ni-B coatings. The coatings were also characterized using field emission scanning electron microscope, energy dispersive x-ray spectroscopy, and x-ray diffraction. The coatings in optimized condition showed no transverse or chevron cracks within 5–24 N.

Modelling and Optimization of Amphoteric Surfactant Concentration in Electroless Nickel Boron Coatings for Maximum Microhardness

In the electroless nickel-boron coating process, surfactant helps to minimize the surface tension between the substrate and the electrolyte in the bath. Despite, its high cost and the formation of micelles from monomeric surfactant molecules at its critical micelle concentration (CMC), it is essential to optimize the concentration while using in the bath. In this study, to solve this problem, mathematical models are developed using regression and artificial neural network (ANN) techniques to relate the concentration of amphoteric surfactant (0-0.162 g/L) as an independent variable and microhardness as a dependent variable. Then, the developed model was used to optimize microhardness at CMC using a genetic algorithm (GA). The goodness of fit of the models was evaluated using the coefficient of determination (R2). The ANN model was found to be the best fit with R2 = 0.99. The maximum microhardness of 852 HV was achieved at the CMC of 0.064 g/L, from the GA using the validated model as a fitness function.

Sub-ps Pulsed Laser Deposition of Boron Films for Neutron Detector Applications.

In view of the demand for high-quality thermal neutron detectors, boron films have recently attracted widespread research interest because of their special properties. In this work, we report on the deposition of boron films on silicon substrates by sub-picosecond pulsed laser deposition (PLD) at room temperature. Particular emphasis was placed on the investigation of the effect of the laser energy density (fluence) on the ablation process of the target material, as well as on the morphological properties of the resulting films. In addition, based on the study of the ablation and deposition rates as a function of the fluence, the ablation/deposition mechanisms are discussed. We show that well-adherent and stable boron films, with good quality surfaces revealing a good surface flatness and absence of cracks, can be obtained by means of the PLD technique, which proves to be a reliable and reproducible method for the fabrication of thick boron coatings that are suitable for neutron detection technology.

In situ probe measurements of plasma parameters during the deposition of boron coatings by the magnetron method

The features of the probe technique are described and the results of measuring the parameters of plasma generated by a planar magnetron sputtering system with a pure boron target during coating deposition are presented. A feature of probe measurements was the use of heating the collecting surface of a single Langmuir probe. Heating led to a decrease in the electrical resistance of the boron film on the surface, which made it possible to carry out in situ probe measurements of the magnetron discharge plasma parameters during the entire process of boron coating. Keywords: plasma parameters, probe method, planar magnetron, boron films.

Electron-Beam Synthesis and Modification and Properties of Boron Coatings on Alloy Surfaces

In this study, fore-vacuum plasma electron beam sources were used to deposit a few micron-thick boron coatings on A284 and ZrNb1 alloys and modify their surfaces. The coating deposition rate with a continuous 1 kW electron beam that evaporated the boron target at a distance of 10 cm was 0.5 µm/min, and the boron coating density was 2.2 g/cm3. Based on the comparison of data on the mass-to-charge composition, beam plasma density, and coating parameters, the contribution of the plasma phase of the evaporated material to the growth of coatings was greater than that of the vapor phase. Using the scanning electron and atomic force microscopy techniques, surface modification by repeated electron beam pulses with electron energies of 8 and 6 keV and a beam power per pulse of 2 J/cm2 and 2.25 J/cm2, respectively, transformed a relatively smooth coating surface into a hilly structure. Based on a structural phase analysis of coatings using synchrotron radiation, it was concluded that the formation of the hilly coating structure was due to surface melting under the repeated action of electron beam pulses. The microhardness, adhesion, and wear resistance of coatings were measured, and their corrosion tests are presented herein. The pure boron coatings obtained and studied are expected to be of use in various applications.

Deposition of boron coatings on surfaces by electron-beam evaporation in forevacuum

We implemented the boron coating deposition on the surface by means of electron-beam evaporation of a crystalline pure boron target (99.9%) and ionization of its vapor at a forevacuum pressure (5–15 Pa). The results of studying the characteristics of this process are presented. The space-angular distribution of the substrate temperature and the distribution of deposition rate for different temperatures of the evaporated target, which is determined by the distribution of boron particles in the volume of the vacuum chamber, were obtained. We give the results of measurements of the plasma composition for three stages of thermal processing of the pure boron target: heating, melting, and intense evaporation. Pure boron coatings on titanium samples at different temperatures were synthesized. The effect of the substrate temperature on the morphology and properties of boron coatings was investigated. It was found that boron in coatings is mostly in an amorphous state, while at the coating boundary it forms chemical compounds with titanium, phases of which were determined using X-ray diffraction pattern method. The results of our work may be useful for a wide range of applications that use thin boron films on various surfaces.

Effect of Morphological and Microstructural Variations on the Properties of Electroless Nickel Boron Coatings

Effect of Morphological and Microstructural Variations on the Properties of Electroless Nickel Boron Coatings

Thermal protective ability of electrochemically deposited nickel and nickel – boron coatings

The thermal protective ability of electrochemically deposited Ni and Ni – B coatings was investigated with the aim of their potential application in the production of lamella-type under-die coolers. It has been established that all studied nickelbased coatings retain thermal stability when heated in an air atmosphere in the temperature range from 500 to 700 °C. At a higher annealing temperature (800 °C), the coatings are oxidised (to the greatest extent the nickel coating) with the formation of an oxide layer up to 7–8 μm thick, the main product of oxidation is Ni0.8Cu0.2O. It is shown that the Ni – B coating with a boron content of 4.5 at. % exhibits the highest thermal stability due to the formation of a film of nickel borate (Ni3(BO3)2) on its surface during annealing. A thin continuous film of borate prevents the contact of atmospheric oxygen with the surface and, accordingly, the formation of mixed oxides of copper and nickel, which are a consequence of the thermal instability of nickel coatings during annealing.

Anti-Erosive Boron and Fluorine Doped Polyimide Coatings for Space Radiation Environment Protection

Anti-Erosive Boron and Fluorine Doped Polyimide Coatings for Space Radiation Environment Protection

Physical features of the functioning of a planar magnetron sputter with a thermaly insulated and heated in discharge target for boron coatings

Physical features of the functioning of a planar magnetron sputter with a thermaly insulated and heated in discharge target for boron coatings

Artificial neural network modelling for average surface roughness in citrate stabilised electroless nickel boron coatings

In this study, electroless nickel boron coatings were developed on Al 7075 aluminium alloy from the citrate stabilised electrolyte bath to investigate the applicability of artificial neural network (ANN) in the prediction of the average surface roughness Ra of the coatings. The process parameters such as concentrations of nickel, reducing agent and stabiliser were considered as input parameters and Ra was selected as an output parameter. Two different feed forward back propagation neural network architectures 3-10-1 and 3-5-5-1, were constructed and trained using Levenberg-Marquardt (LM) algorithm to predict the Ra. The accuracy of the networks was compared with the predicted coefficient of determination (R2) and mean squared error (MSE). The R2 and MSE of 0.9998 and 6.32E-05 were obtained for 3-5-5-1 against 0.9850 and 6.29 E-04 for 3-10-1 network architecture, which proved that the multi-layer perceptron (3-5-5-1) fits well for the experimental data presented.

Modelling and optimisation of hardness in citrate stabilised electroless nickel boron (ENi-B) coatings using back propagation neural network – Box Behnken design and simulated annealing – genetic algorithm

ABSTRACT In this work, a novel citrate stabilised electroless bath was developed and the process parameters (concentrations of nickel, reducing agent, and stabiliser) were optimised to achieve the maximum hardness in the ENi-B deposit on 7075-T6 aluminium alloy, using the back-propagation neural network (BPNN), Box–Behnken design (BBD), simulated annealing (SA) and genetic algorithm (GA). The effect of independent variables on dependent variable was modelled using the BPNN and BBD. The models were assessed for their significance using the coefficient of determination (R2) and mean squared error (MSE). The MSE and R2 of 34.18 and 0.9852 were obtained for BPNN model against 20.48 and 0.9911 for BBD, which proved that the BBD fits well to the experimental data. The optimum nickel ion, reducing agent and stabiliser concentrations of 29.86, 0.77 and 30.92 g L−1 were obtained from BBD for the maximum hardness of 592 HV. The local optimum values obtained from BBD were compared with global optimisation techniques, SA and GA, and the values were validated through experiments carried out in triplicate. The maximum hardness from local and global optimisation techniques was identical, with negligible change in the values of optimised process parameters. X-ray diffraction and scanning electron microscopy methods were used to examine the elemental composition and surface morphology, respectively, before and after heat treatment.

Ion implantation of helium and hydrogen in boron coatings

The work presents the calculated mean free paths of hydrogen, deuterium and helium ions in boron-carbon and boron-titanium films of various configurations. Has been rated impact of these coatings at various film thicknesses for ion capture in tungsten. The calculations were carried out using the software package SRIM-2012, for each mileage value was calculated by modeling of10,000 cascades.