Showing papers in "Surface Engineering in 2012"
TL;DR: In this article, WC-12Co coating has been deposited using plasma spray and high velocity oxyfuel spraying (HVOF) and wear performances of these coatings have been compared with electroplated hard chrome.
Abstract: In the present study, WC–12Co coating has been deposited using plasma spray and high velocity oxyfuel spraying (HVOF) and wear performances of these coatings have been compared with electroplated hard chrome. Bearing steel and WC–Co balls have been used as rubbing counterparts. The wear is predominantly adhesive for the atmospheric plasma spray (APS) and the electroplated coating. For HVOF coating, wear has been found to occur by localised microfracture. A careful choice of plasma spray parameters yields a coating more wear resistant than the electroplated hard chrome. However, the HVOF coating has always offered the highest wear resistance.
59 citations
TL;DR: In this paper, the erosion wear behavior of WC-Co base thermal spray coatings was investigated at impact angles of 30 and 90° using SiC particles of ∼50 μm in diameter as erodent, at a velocity of 83·4 m s−1.
Abstract: The present investigation has been carried out in order to study the erosion wear behaviour of WC–Co base thermal spray coatings. WC–12Co and WC–10Co–4Cr coatings were deposited by means of high velocity oxygen fuel (HVOF) thermal spraying. The erosion tests were conducted at impact angles of 30 and 90° using SiC particles of ∼50 μm in diameter as erodent, at a velocity of 83·4 m s−1. It has been found that the erosion rate for both coated systems was higher when the test was carried out at an angle of 90°. The through-thickness residual stresses of the coatings, as well as the microstructural characterisation, allowed an explanation of the results and the erosion mechanisms in each case. It has been found that, under the experimental conditions carried out in the present study, the WC–10Co–4Cr coating exhibited a higher erosive wear resistance as compared to the WC–12Co coating.
40 citations
TL;DR: In this paper, the authors compared the structure and properties of nickel, cobalt and nickel-cobalt alloy coatings obtained from ionic liquid (IL) with those obtained from aqueous electrolyte.
Abstract: The aim of the present study is to compare the structure and properties of nickel, cobalt and nickel–cobalt alloy coatings obtained from ionic liquid (IL) with those obtained from aqueous electrolyte. Choline chloride, a cheap and non-toxic IL, has been chosen for electrodeposition. The coatings obtained from IL displayed higher microhardness compared with those obtained from aqueous electrolyte. A difference in the surface morphology was observed. X-ray diffraction studies showed that the nickel rich coatings exhibited face centred cubic crystal structure, whereas those rich in cobalt displayed hexagonal close packed structure. Comparison in the corrosion behaviour of the coatings showed that the Ni coating possessed better corrosion resistance irrespective of the electrolyte adopted.
40 citations
TL;DR: In this paper, the Ni base alloy powder was modified by adding tungsten carbide (10 and 20 wt-%) and CeO2 to study their effects on the microstructure, microhardness and abrasive wear behaviour of unmodified and modified coatings.
Abstract: The Ni base alloy (EWAC 1004EN) was used to develop coatings on the mild steel substrate by flame spraying process. The Ni base alloy powder was modified by adding tungsten carbide (10 and 20 wt-%) and CeO2 to study their effects on the microstructure, microhardness and abrasive wear behaviour of unmodified and modified coatings. All the coatings were subjected to remelting using tungsten inert gas arc welding. The abrasive wear behaviour of all the coatings in different conditions was studied using different normal loads (5, 10, 15 and 20 N) against 120 and 600 grit size abrasive medium. Scanning electron microscopy analysis of the worn out surfaces was carried out to understand the wear mechanisms. It was observed that the remelting of the coatings increased the hardness of WC and CeO2 modified flame sprayed coatings by ∼35%, while the abrasive wear resistance increased by 1·5- to threefold.
39 citations
TL;DR: In this article, a multilayer skin dressing consisting of castor oil based polyurethane (PU) as the outer layer and two biopolymeric layers of heparin and chitosan as the inner layers were prepared.
Abstract: The aim of this study is to design an artificial skin dress. A multilayer skin dressing included synthesised castor oil based polyurethane (PU) as the outer layer and two biopolymeric layers of heparin and chitosan as the inner layers were prepared. The surface of PU film was activated using two steps oxygen radio frequency plasma treatment. The surface of the modified PU films characterised by attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy and water drop contact angle measurements. Scanning electron microscopy observations confirmed the presence of grafted poly acrylic acid on the surface of PU films. Also, heparin and chitosan were immobilised on PU films. In vitro cell culture showed that the samples have an excellent biocompatibility with L929 fibroblast cells. Cell adhesion and proliferation of cells on the chitosan/heparin immobilised surfaces showed better behaviours compared with poly (acrylic acid) grafted PU film.
32 citations
TL;DR: In this article, the microstructure and mechanical properties of bilayer bilayer coatings were investigated using TEM and SEM, and the results showed that the deposited coatings are characterised by compact structure without delamination or defects and that they closely adhere to each other.
Abstract: Investigation results concerning microstructure and mechanical properties of the bilayer coatings are presented in this work. Gradient/monolithic coatings [Ti/Ti(C,N)-gradient/CrN, Cr/CrN-gradient/CrN] were deposited onto the aluminium alloy (Al–Si–Cu) substrate by cathodic arc evaporation method. The microstructure of the achieved layers was examined using TEM and SEM. Change of the chemical composition was measured using a glow discharge optical emission spectrometer. The physical vapour deposition coating structure is composed of small crystallites with an average size between 15 and 20 nm, depending on the coating type. Images (SEM) showed that the deposited coatings are characterised by compact structure without delamination or defects and that they closely adhere to each other. The Ti(C,N)/CrN coatings demonstrate the highest hardness and abrasive wear resistance.
31 citations
TL;DR: In this paper, a black polyvinyl chloride electrical insulation tape has been found to be a good choice as a sacrificial coating for laser peening of smooth metallic surfaces where black paint does not adhere well.
Abstract: Laser shock peening usually requires the presence of a sacrificial coating to protect the substrate from undesirable thermal effects generated by laser irradiation. This paper describes an experimental study to identify an adherent sacrificial coating for laser peening of smooth metallic surfaces where black paint does not adhere well. Normal black polyvinyl chloride electrical insulation tape has been found to be a good choice as a sacrificial coating. Laser peening with black insulation tape generated effective laser peening in three different substrates, namely, Ti6Al4V alloy, SAE 9260 spring steel and DIN X20Cr13 martensitic stainless steel. The depth of peening was comparable or better than that generated with black paint. With respect to widely used black paint, black insulation tape not only provides clean, simple and uniform coating but also literally eliminates the time involved in its application (black paint requires multilayer coating with long intermediate curing periods) and removal.
29 citations
TL;DR: In this article, the effects of precursor concentration and annealing temperature on the physical properties of ZnO thin films were investigated and it was shown that the post-annealing process has significant impact on the quality of the films.
Abstract: ZnO thin films were deposited onto glass substrates using sol–gel spin coating technique from starting solutions having different precursor concentrations (0·1, 0·3 and 0·5M). The effects of precursor concentration and annealing temperature on the physical properties of the films were investigated. The X-ray diffraction studies confirm that all the films have preferential orientation along the (002) plane with hexagonal wurtzite structure. The optical transparency gradually decreases (from 95 to 80%) as the precursor concentration increases. The optical energy gap is in the range of 3·18–3·32 eV. The systematic study shows that the post-annealing process has significant impact on the quality of the films. The SEM images depict that the grain size decreases as the precursor concentration increases, and the AFM images show that the film annealed at 550°C has well defined uniform grains. The lowest dislocation density is observed for 0·3M annealed at 550°C.
27 citations
TL;DR: In this paper, the microstructure of a polyhedron and petaline shaped reinforced Ni-based coating on Ti-6Al-4V was characterised by SEM, energy dispersive spectroscopy and X-ray diffraction.
Abstract: TiC reinforced Ni based coating on Ti–6Al–4V was produced by laser cladding using colloidal graphite powder and pure nickel powder. The microstructure was characterised by SEM, energy dispersive spectroscopy and X-ray diffraction. Microhardness and dry sliding wear properties were investigated, and the results showed that diffusion of the substrate atoms had caused significant in situ growth of TiC and solid solution strengthening in the coating. TiC was polyhedron and petaline shaped. After laser cladding, the microhardness profile presented novel changes with depth in the coating. The TiC reinforced Ni based coating had good wear resistance on ball on disc dry sliding wear testing. Abrasive wear was the main mechanism.
27 citations
TL;DR: In this article, the porosity level of alumina coatings was evaluated by the digital image analysis method and an attempt was also made to develop an empirical relationship to predict the porosa level of the alumina coating, where three factors five level central composite rotatable design matrix was used to minimize the number of experimental conditions.
Abstract: Alumina coating was deposited on AZ31B magnesium alloy using atmospheric plasma spraying process by varying parameters such as power, stand-off distance and powder feedrate. The porosity level of alumina coatings were evaluated by the digital image analysis method. An attempt was also made to develop an empirical relationship to predict the porosity level of alumina coatings. Three factors five level central composite rotatable design matrix was used to minimise the number of experimental conditions. Response surface methodology was used to develop the relationship. The developed relationship can be effectively used to predict the porosity level of alumina coatings at 95% confidence level. The results indicate that the input power has the greatest influence on porosity level of the coatings, followed by stand-off distance and powder feedrate.
27 citations
TL;DR: A layer of nickel-phosphorus alloy was electroless plated on the surface of microarc oxidised AZ31 magnesium alloy first, and then sealing treatment was performed on the electroless nickel plated coating using bis-(triethoxysilylpropyl)tetrasulphide silane.
Abstract: A layer of nickel–phosphorus alloy was electroless plated on the surface of microarc oxidised AZ31 magnesium alloy first, and then sealing treatment was performed on the electroless nickel plated coating using bis-(triethoxysilylpropyl)tetrasulphide silane. Fourier transform infrared spectroscopy, scanning electron microscope (SEM), energy dispersed X-ray spectroscope analyses, electrochemical techniques and immersion test were used for the analyses of surface morphology and structure and corrosion resistance of electroless nickel plated samples before and after sealing treatment. The results showed that the silane film by sealing treatment improves its corrosion resistance significantly.
TL;DR: In this paper, traditional and modified Y2O3 stabilised zirconia (YSZ) thermal barrier coatings (TBCs) on nicked based superalloy DZ125 were produced by atmospheric plasma spray.
Abstract: Traditional and modified Y2O3 stabilised zirconia (YSZ) thermal barrier coatings (TBCs) on nicked based superalloy DZ125 were produced by atmospheric plasma spray. In addition to the thermal properties, the mechanical properties of ceramics are also very important for superior TBCs. The mechanical properties of the sprayed coatings at room temperature, including microhardness, Young’s modulus, fracture toughness and tensile strength, were evaluated. The Young’s modulus and microhardness of the segmented coating were measured to be about 72 and 8 GPa, relatively higher than those of the non-segmented coating respectively. The fracture toughness was determined by an indentation technique. The values of 1·7–2·0 MPa m1/2 for the traditional YSZ coatings are relatively lower than the values for the modified YSZ coatings 2·0–2·3 MPa m1/2. The lower porosity and better lamellar bonding of the segmented coating could be responsible for the improvement of the mechanical properties.
TL;DR: In this paper, an equivalent circuit diagram based on blocked and partially corroded surface characterisations was proposed, and good agreement was observed between theoretical impedance spectra obtained on the basis of the equivalent circuit and spectra recorded during the measurements.
Abstract: Electrochemical impedance spectroscopy of Ni and Ni–ZrO2 composite coatings was studied. Investigation of corroded surfaces showed that the cluster boundaries in pure Ni and weak bonds between Ni matrix and ZrO2 particles in Ni–ZrO2 composite coating are the appropriate paths for corrosion to proceed. An equivalent circuit diagram based on blocked and partially corroded surface characterisations was proposed, and good agreement was observed between theoretical impedance spectra obtained on the basis of the equivalent circuit and spectra recorded during the measurements. Changes of microstructure and corrosion proceeding paths were recognised as the reasons for the higher corrosion resistance of Ni–ZrO2 with respect to pure Ni.
TL;DR: In this article, one-pot hydrothermal method was used for modifying a wood surface by the deposition of anatase TiO2/ZnO coating at a relatively low temperature.
Abstract: In this work, one-pot hydrothermal method was used for modifying a wood surface by the deposition of TiO2/ZnO coating at a relatively low temperature. The prepared wood samples were characterised using SEM, energy dispersive X-ray analysis and powder X-ray diffraction. Results showed that wood surface was coated by anatase TiO2 and wurtzite structured ZnO at 110°C. To explore the flameproof properties of the modified wood, cone calorimetry technique was employed to measure the significant difference in combustion parameters between the untreated and the treated wood. As compared with the untreated wood sample, the time to ignition was 37 s, increasing about four times; the burning duration was around doubled, and smoke production rate and total smoke production were almost zero. As a result, the treated wood had an improved fire resistance, and one-pot hydrothermal method was a feasible method to fabricate non-flammable wood materials.
TL;DR: In this paper, the AISI 1060 steel was pack chromised for 6 and 9 hours at 1000 and 1050°C using different activator concentrations. And the results showed that the results yielded the formation of layers with high chromium concentrations, high hardness and wear resistance.
Abstract: Pack chromising treatment is an environmentally friendly alternative to hard chromium to form wear and corrosion resistant surface layers. In this work, samples of AISI 1060 steel were pack chromised for 6 and 9 h at 1000 and 1050°C using different activator concentrations. Wear tests were performed in dry conditions and corrosion tests in natural sea water for the pack chromised samples and hard chromium. Pack chromising yielded the formation of layers with high chromium concentrations, high hardness and wear resistance. Increasing activator concentration causes no significant change on the morphology and thickness of the layers. The layers produced at 1050°C yielded only a (Cr,Fe)2N1−x phase, and those obtained at 1000°C are composed of a carbide mixture with (Cr,Fe)2N1−x. The sample treated at 1050°C for 9 h resulted in an optimum condition by means of better wear resistance and corrosion properties, which were close to that exhibited by the hard chrome, indicating that pack chromising is a pro...
TL;DR: In this article, structural and mechanical properties of WO3 thin films deposited on glass substrates at different temperatures by radio frequency reactive magnetron sputtering are presented, showing that scratch hardness increases with the rise of temperature, indicating improved penetration and wear resistance at temperatures up to 300°C.
Abstract: This study presents structural and mechanical properties of WO3 thin films deposited on glass substrates at different temperatures by radio frequency reactive magnetron sputtering. WO3 films deposited at temperatures up to 200°C are found as amorphous, but crystalline at 300 and 400°C. Chemical analysis reveals the overstoichiometry of the films. The diffusion of sodium ions from glass substrates occurs at higher temperatures. The adhesion critical loads of WO3 films deposited at room temperature and at 200, 300 and 400°C are found to be 670, 990, 1080 and 830 mN respectively using microscratch tests with a 25 μm probe. Scratch hardness increases with the rise of temperature. The depth of penetration and wear track width decrease with temperature, indicating an improved penetration and wear resistance at temperatures up to 300°C. Scanning electron microscopy images reveal that the coatings fail due to wedge and recovery spallation during scratch and wear tests respectively.
TL;DR: In this article, an amine free sol-gel method for silica coating of Au nanoparticles was described and an X-ray image of a colloid solution of the silica coated Au (Au-SiO2) particles was shown.
Abstract: This paper describes an amine free sol–gel method for silica coating of Au nanoparticles and shows an X-ray image of a colloid solution of the silica coated Au (Au–SiO2) particles. The Au nanoparticles that had a size of 16·9±1·2 nm were prepared through a conventional citrate reduction method. The silica coating was performed with a sol–gel reaction of tetraethylorthosilicate (TEOS) catalysed with NaOH in the presence of Au nanoparticles. The silica shell thickness was varied from 37 to 68 nm for TEOS concentrations of 1×10−3–20×10−3M at 4·3×10−5M of Au, 10·7M of H2O and 1·0×10−3M of NaOH. The optical properties of the Au–SiO2 particle colloid solution were related to the refractive index around the Au particles and the intensity of scattering from silica shells. The as prepared colloid solution could be concentrated up to an Au concentration of 4·3×10−2M with salting out. The concentrated colloid solution showed a high contrast X-ray image.
TL;DR: In this paper, the influence of post-vacuum heat treatment on the microstructure, phase composition, microhardness and wear resistance of Tungsten carbide (WC) and 2C-Ni coatings has been investigated.
Abstract: Tungsten carbide (WC)–(W,Cr)2C–Ni coatings have been deposited by high velocity oxyfuel spraying. The influence of post-vacuum heat treatment on the microstructure, phase composition, microhardness and wear resistance of the coatings has been investigated, which is conducted based on analyses of the microstructure and phase composition evolution of the coatings by scanning electron microscopy and X-ray diffraction, as well as measurement of their microhardness with a microhardness tester and evaluation of their friction and wear behaviour with an oscillating friction and wear tester. Results show that after heat treatment above 600°C, crystallisation of amorphous phases occurs, and some new phases rich of Fe and C are generated in the coatings. Moreover, the microhardness and wear resistance of WC–(W,Cr)2C–Ni coatings increase with increasing heat treatment temperature up to 600 and 700°C, but they tend to decrease with further elevating heat treatment temperature.
TL;DR: Gadolinium based conversion coating, a new chemical protective coating for magnesium alloys, was prepared and its microstructure and corrosion resistance were investigated in this paper, which indicated that the morphology of the coating is a cracked mud structure.
Abstract: Gadolinium based conversion coating, a new chemical protective coating for magnesium alloys, was prepared and its microstructure and corrosion resistance were investigated. The micromorphology, composition and elemental chemical states were observed by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS) respectively. The corrosion resistance was evaluated by a potentiodynamic polarisation curve and electrochemical impedance spectroscopy. Nanomechanics integrated test system was used to represent the nanomechanical property and residual stress. The results indicate that the morphology of the coating is a cracked mud structure. The EDS and XPS results reveal that the coating is primarily made of magnesium and gadolinium oxides. Gadolinium coating forming mechanism can be generally divided into two periods: the dissolution of the substrate, the codeposition of Gd(OH)3 and Mg(OH)2. The potentiodynamic polarisation curve and electrochemica...
TL;DR: In this article, high velocity arc spraying and cold gas dynamic spraying were applied to prepare the aluminium coating, and electrochemical impedance spectroscopy measurement in combination with scanning electron microscopy analysis of corrosion surface and X-ray diffraction results of corrosion product were used to compare the corrosion behaviour of these two coatings.
Abstract: High velocity arc spraying and cold gas dynamic spraying were applied to prepare the aluminium coating, and electrochemical impedance spectroscopy measurement in combination with scanning electron microscopy analysis of corrosion surface and X-ray diffraction results of corrosion product were used to compare the corrosion behaviour of these two coatings. It was found that there was sparse and porous corrosion product covering on the surface of the arc sprayed aluminium coating through which the Cl− can penetrate into the inner coating interface. In contrast, the surface of the cold sprayed aluminium coating after immersion was less porous and tended to seal the pores in the coating. This kind of structure can obstruct the penetration of corrosion medium into the inner coating surface and reduce the corrosion rate to a certain extent. In addition, the diffusion impedance O was introduced in the electrochemical impedance spectroscopy modelling for the purpose of getting good fitting results.
TL;DR: In this paper, an electrochemical polarisation technique was employed to measure the porosity of Ni-P and composite coatings in as plated condition, based on the changes observed in the corrosion potential with varying cathode and/or anode area on a bimetallic corroding system.
Abstract: Ni–P composite coatings containing SiC nanoparticles or carbon nanotubes (CNTs) were deposited on steel substrates via electroless plating technique An electrochemical polarisation technique was employed to measure the porosity of Ni–P and composite coatings in as plated condition The technique was based on the changes observed in the corrosion potential with varying cathode and/or anode area on a bimetallic corroding system Electrochemical impedance spectroscopy (EIS) test was used to assess the corrosion resistance of the coatings Results showed that incorporation of nanoscaled second phases could decrease the area fraction of porosity from 2··5×10−5 for Ni–P coating to 2×10−7 for Ni–P–CNT coating Ni–P–CNT coating exhibited the least porosity that it could be attributed to the morphology of CNTs and their ability to fill out the pores more effectively as compared to SiC nanoparticles EIS results were in agreement with the porosity results as Ni–P–CNT coatings illustrated the highest corrosion resi
TL;DR: In this article, a choline chloride-ethylene glycol deep eutectic solvent containing CdCl2 and ZnCl2 was investigated via linear sweep voltammetry, and the result revealed that the CdZn alloy was codeposited when the deposition potential was prolonged to the potential range, leading to insufficient zinc deposition on the copper electrode.
Abstract: Cadmium–zinc alloy coatings were successfully electrodeposited on copper electrodes from a choline chloride–ethylene glycol deep eutectic solvent containing CdCl2 and ZnCl2. The electrochemical behaviour of the electrolyte system was investigated via linear sweep voltammetry, and the result revealed that the CdZn alloy was codeposited when the deposition potential was prolonged to the potential range, leading to the insufficient zinc deposition on the copper electrode. The scanning electron microscopy results demonstrated that the morphologies of codeposits were cauliflower-like. The codeposition mechanism was also investigated, and the dependencies of the Cd content in the CdZn codeposit on the deposition potential, Cd(II) molar ratio and temperature were discussed.
TL;DR: In this article, nano-alumina coatings have been applied on SS 304 substrate using atmospheric plasma spray process and the tribological performance of the nano alumina coating is investigated and compared with conventional coatings.
Abstract: Nanostructured alumina coatings have been deposited on SS 304 substrate using atmospheric plasma spray process. In the present work, nanostructured feed powder is obtained by manual granulation of nano-Al2O3 powder particles followed by exhaustive sieving, which is helpful in their proper consolidation. The tribological performance of the nano-alumina coatings, such as dry sliding, slurry erosion and cavitation erosion, has been investigated and compared with conventional coatings. The superior wear and erosion resistance of nanostructured coatings as compared to conventional coatings are due to its higher hardness and effective hindrance to crack propagation. Wear mechanism was explained based on their microstructure and worn surface morphologies. The microhardness and porosity of the two coatings were also experimentally investigated.
TL;DR: In this paper, two different surfactants, namely sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB), were studied for their ability to alter the performance characteristics of plating baths as well as composite membranes.
Abstract: Nickel–ceramic microfiltration membranes were prepared by electroless deposition of nickel on the activated ceramic membrane substrates having a nominal pore size of 275 nm. Two different surfactants, namely sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB), were studied for their ability to alter the performance characteristics of plating baths as well as composite membranes. Parameters evaluated include the bath conversion, plating efficiency, metal film thickness, average pore size of the composite membranes and per cent pore densification. The overall plating rate was found to increase up to 32% with the addition of SDS and 45% with the addition of CTAB. Addition of surfactants not only resulted in increased film thickness (4–5 μm) but also accounted for considerable reduction in average pore size of the composite membrane. CTAB was found to be more effective and efficient than SDS for nickel membrane fabrication.
TL;DR: The efficiency of atmospheric pressure plasma treatment can be highly enhanced by simultaneous high power ultrasonic irradiation onto the surface of the treating surface as discussed by the authors, which is because ultrasonic waves with a...
Abstract: Efficiency of atmospheric pressure plasma treatment can be highly enhanced by simultaneous high power ultrasonic irradiation onto the treating surface. It is because ultrasonic waves with a...
TL;DR: In this article, NiCrAlY coatings were applied on steel substrate using high velocity oxygen fuel spraying process and the spray parameters were varied in order to study their influence on the coating properties.
Abstract: In the present study, NiCrAlY coatings were applied on steel substrate using high velocity oxygen fuel spraying process. The spray parameters were varied in order to study their influence on the coating properties. Powder and coating microstructures were investigated by a combination of X-ray diffraction, optical and scanning electron microscopy as well as energy dispersive spectroscopy analysis. Bond strength and microhardness tests were also performed on the coatings. It was found that the propane flowrate, the oxygen flowrate, the spray distance and powder feedrate have a significant effect on the coating characteristics. Finally, with the aim of minimising oxygen content and maximising bond strength, the optimum parameters were selected as the preferred spray parameters.
TL;DR: The NiCrBSi+Ta coating exhibited higher fracture toughness, and higher abrasive and adhesive wear resistance than the NiCrbsi coating as mentioned in this paper, and the primary wear mechanism was abrasion and microflaking under a low load (30 N), and adhesion and oxidation under a high load (75 N).
Abstract: Ta was added to laser clad NiCrBSi coating to improve wear resistance. In situ synthesised TaC particles of nearly equiaxed shape were uniformly dispersed in the coating. The colony that contained acicular Cr rich boride or carbide grew radially around the TaC particle and had a strong bond with the particle. The TaC particles had good bonds with the matrix, and tended to be crushed and impressed into the matrix instead of being pulled out from the wear surface during the wear process. The NiCrBSi+Ta coating exhibited higher fracture toughness, and higher abrasive and adhesive wear resistance than the NiCrBSi coating. The primary wear mechanism of the NiCrBSi+Ta coating was abrasion combined with the oxidation process under all test conditions while the main wear mechanism of the NiCrBSi coating was abrasion and microflaking under a low load (30 N), and adhesion and oxidation under a high load (75 N).
TL;DR: In this article, thermal spray-based coatings of yttrium oxide powder were developed using numerical simulation of particle behavior in the thermal plasma jet and experimental method to develop the coatings.
Abstract: Plasma sprayed coatings of yttrium oxide, exhibiting good adhesion and thermal shock resistance, were developed on various substrates using thermal spray grade yttrium oxide powder developed in our laboratory. Numerical simulation of particle behaviour in the thermal plasma jet was combined with experimental method to develop the coatings. Phase structure and microstructural characterisation of the deposits were evaluated by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. Deposition efficiencies and adhesion strength of the coatings deposited at different power levels could be well explained with the predictions provided by the model. The process was optimised using deposition efficiency as the response parameter.
TL;DR: In this article, the authors compared the behavior of cobalt and iron base hardfacing alloys on hot forging dies under temper, shock and wear, and found that the cobalt base hardface alloy possesses excellent shock hardening properties at all the experimental temperatures.
Abstract: This paper aims to compare the behaviour of cobalt and iron base hardfacing alloys on hot forging dies under temper, shock and wear. Tempering resistance, shocking behaviour and wear resistance were investigated using a tubular furnace, press and pin on disc tribometer respectively. The results showed that the thermal stability of commercial iron base hardfacing alloy (named RMD248) is good below 550°C but poor in the case of higher temperature, whereas the cobalt base hardfacing alloy presents superior tempering resistance. The cobalt base hardfacing alloy possesses excellent shock hardening properties at all the experimental temperatures, but RMD248 does not, especially at high temperature (600°C). Compared with the hardfacing layer produced by RMD248, the cobalt base hardfacing layer produces high wear resistance at 600°C and high temperature oxidation resistance at 600°C for 100 h.
TL;DR: In this paper, Ni high cerium oxide nanocomposite coatings were prepared by electrodeposition process using inexpensive and particle free aqueous baths containing NiCl2.6H2O and CeCl3.7H2 O salts.
Abstract: Ni high cerium oxide nanocomposite coatings were prepared by electrodeposition process using inexpensive and particle free aqueous baths containing NiCl2.6H2O and CeCl3.7H2O salts. Scanning electron microscopy, atomic force microscopy, EDAX and X-ray diffraction studies showed the possibility of deposition of nickel containing 35% cerium oxide composite coating. Electrochemical impedance spectroscopy and potentiodynamic data indicated that the presence of cerium oxide in the Ni deposit led to an increase in electrocatalytic activity in hydrogen evolution.