Showing papers in "Surface Engineering in 2007"
TL;DR: Pt/Ti and Pt/TiO2 electrodes were made by galvanic deposition of platinum metal from an acid plating bath containing cis-dinitro-diammin-platinum(II) complex (P salt) onto titanium and anodic TiO2 layer on titanium substrates respectively.
Abstract: Pt/Ti and Pt/TiO2 electrodes were made by galvanic deposition of platinum metal from an acid plating bath containing cis-dinitro-diammin-platinum(II) complex (P salt) onto titanium and anodic TiO2 layer on titanium substrates respectively. Titanium oxide nanotubes were fabricated by anodising titanium foil in acid solution. Pt/Ti and Pt/TiO2 electrodes were characterised using electrochemical methods and scanning electron microscopy. Cyclic voltammetric analysis of Pt/Ti electrodes in dilute sulphuric acid yields voltammograms with features characteristic of bulk polycrystalline platinum electrodes. In contrast, the voltammograms for Pt/TiO2 electrodes are not quantitatively similar to those for smooth polycrystalline platinum electrodes. Voltammetry in potassium ferricyanide yields reversible voltammograms, indicating the good electrical conductivity of and connectivity between the deposited platinum and substrates and hence the absence of any significant resistive surface oxide film. The electro...
43 citations
TL;DR: In this paper, the authors showed that S phase can be formed in Co-Cr alloys during low temperature plasma carburising, which can significantly improve the wear resistance of metal joints.
Abstract: One of the major concerns over long term metal on metal articulations is the carcinogenic effect of metal particles. How to improve the surface hardness and wear resistance of Co–Cr–Mo alloys and thus extend the life span of the metal on metal joint prostheses is a timely task from both a scientific and clinical viewpoint. The present investigation indicated that plasma carburising a Co–Cr alloy between 400 and 600°C can produce a hardened layer on the surface which can significantly improve its wear resistance. Detailed structural, composition and microstructural characterisation have advanced the scientific understanding of the hardening effect. This is the first report that S phase can be formed in Co–Cr alloys during low temperature plasma carburising.
42 citations
TL;DR: In this paper, cast Mg alloys, AZ61 and AZ91, were subjected to laser treatments with a view to modifying surface/subsurface microstructure and improving the micro-structure assisted localised corrosion resistance of the alloys.
Abstract: Poor corrosion resistance is a major obstacle in widespread application of Mg alloys. In the present study, cast Mg alloys, AZ61 and AZ91 were subjected to laser treatments with a view to modifying surface/subsurface microstructure and improving the microstructure assisted localised corrosion resistance of the alloys. Comparison of the laser treated surface microstructure with the bulk microstructure, as observed by reflected light microscopy demonstrates significant alterations. Immersion and anodic polarisation tests of the laser treated and untreated specimens in sodium chloride solution have suggested a variation in corrosion behaviour with improvements in corrosion resistance.
38 citations
TL;DR: In this paper, a comparative study of the microstructure, hardness and cavitation erosion behaviour of Ti-6Al-4V laser nitrided under different gas atmospheres with nitrogen concentrations of 0-25%.
Abstract: The present paper reports on a comparative study of the microstructure, hardness and cavitation erosion behaviour of Ti–6Al–4V laser nitrided under different gas atmospheres with nitrogen concentrations of 0–25%. By varying the nitrogen content of the gas atmosphere, the structure and hence the hardness and cavitation erosion behaviour of the laser nitrided layers can be controlled in a wide range. With increasing nitrogen content of the gas atmosphere, the structure within the laser nitrided layers characteristically changed from martensitic a9-Ti to a fine mixture of a- and b-Ti grains, finally leading to the formation of different titanium nitrides. The study revealed that the increase of hardness and cavitation erosion resistance can be mainly attributed to solid solution hardening of the nitrogen. It is shown that optimum cavitation erosion resistance is only achieved if crack free layers containing no brittle titanium nitrides are produced.
37 citations
TL;DR: In this paper, a magnetron sputtering from a Ti3SiC2 target onto electrical contact components at a temperature below 300°C was used to produce nanocomposite coatings with a relatively high nanoindentation hardness of 20 GPa.
Abstract: Nanocomposite coatings consisting of TiC nanocrystallties embedded in an amorphous SiC matrix (nc-TiC/a-SiC) have been produced using magnetron sputtering from a Ti3SiC2 target onto electrical contact components at a temperature below 300°C. The as deposited nanocomposites were employed as electrical contact materials. Results show that when contacted against Ag, they exhibit somewhat higher contact resistance than Ag against Ag, while preventing welding and potentially minimising wear. This is due to an adequate resistivity coupled with beneficial mechanical properties. The design of the nanoscale materials produced coatings with a relatively high nanoindentation hardness of 20 GPa, but with a ductile deformation behaviour. The ductility is explained by rotation and gliding of nc-TiC grains in the matrix. Therefore, the nanocomposite material can minimise problems with wear and welding while retaining low contact resistance. Consequently, this type of novel coating with appropriate mechanical properties offers a solution to problems in many electrical applications. Moreover, the use of physically vapour deposited coatings is promoted in some previously relatively unexploited areas of electrical contact applications. © 2007 Institute of Materials, Minerals and Mining.
35 citations
TL;DR: In this paper, Ni-P-ZrO2 composite coatings on AZ91D magnesium alloys were developed and their characteristics were investigated, and the experimental results showed that they were uniform and compact.
Abstract: Electroless Ni-P-ZrO2 composite coatings on AZ91D magnesium alloys was developed and their characteristics were investigated. The experimental results showed that the composite coatings were uniform and compact. The hardness of Ni-P-ZrO2 composite coatings reached the maximum value at 350 degrees C heat treatment, and then decreased at 400 degrees C. The nickel phosphor alloys provided solution strengthening and precipitation strengthening, while the ZrO2 nanoparticles provided dispersion hardening, making the composite coatings harder than that of Ni-P coatings. The wear resistance of Ni-P-ZrO2 composite coatings was obviously superior to Ni-P coatings, especially with longer wear time, which can be attributed to the dispersion strengthening and load support effect of ZrO2 in the coatings. The Ni-P-ZrO2 coatings exhibited better corrosion resistance than that of Ni-P coatings owing to codeposition of ZrO2 together with NiP leading to a more compact composite coating.
35 citations
TL;DR: In this article, a low temperature plasma surface alloying with both nitrogen and carbon simultaneously was used to increase the surface hardness and wear resistance of medical grade austenitic stainless steels, such as ASTM F138 and F1586.
Abstract: Low temperature surface alloying with either nitrogen (nitriding) or carbon (carburising) has been successfully employed in hardening AISI 316. However, little work has been directed towards low temperature plasma surface alloying with both nitrogen and carbon simultaneously. In addition, little or no research has been conducted on the surface modification of medical grade austenitic stainless steels, such as ASTM F138 and F1586. In the present study, plasma surface alloying treatments have been conducted on medical grade ASTM F138 and ASTM F1586 as well as on engineering grade AISI 316 for comparison. Systematic materials characterisation was carried out using optical microscopy, glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). The three stainless steels had similar response to the plasma alloying treatments. At a temperature of 425°C plasma surface alloying with both carbon and nitrogen can effectively increase the surface hardness and wear resistance of the thre...
31 citations
TL;DR: In this paper, a tribological test aimed at the simulation of aluminium hot extrusion was performed, where a 6082-Al disc, induction heated up to a maximum surface temperature of 350°C, is allowed to rotate against a conformal hot work steel block, simulating the extrusion die.
Abstract: A tribological test aimed at the simulation of aluminium hot extrusion was performed. A 6082-Al disc, induction heated up to a maximum surface temperature of 350°C, is allowed to rotate against a conformal hot work steel block, simulating the extrusion die. The test simulates the wear mechanism observed under in service conditions. After an initial period, the hot plasticised Al progressively adheres to the steel counterpart thus allowing direct Al–Al contact. The high shear stresses given by the strong adhesion produce the nucleation of deep cracks which strongly deteriorate the surface of the steel by delamination. Hot work tool steel (AISI H11) is employed as extrusion dies. Salt bath nitriding (Tenifer) is usually carried out to improve wear resistance. The possible application of PVD (CrN, TiAlN) and CVD (TiC + TiN) hard coatings, exhibiting lower compatibility versus Al, has been evaluated in the present work. The occurrence of two distinct damage regimes was detected. Regime 1 shows minor e...
31 citations
TL;DR: In this article, the authors evaluated the boron mobility at the material surface of borided steels AISI 1045 and M2 during the paste boriding process.
Abstract: The present study evaluates the boron mobility at the material surface of borided steels AISI 1045 and M2 during the paste boriding process. This surface hardening technique produces two characteristic phases on the material, FeB, Fe2B and a transition zone, denominated diffusion zone, in the layer/substrate interface. The thermochemical treatment was performed at three different temperatures: 1193, 1223, 1273 K and two treatment times: 2 and 6 h for the 1045 steel, and 1223, 1253 and 1273 K with the same treatment times for M2 steel, modifying the boron potentials in equilibrium at the substrates surfaces. By using the mass balance equation, and assuming a linear concentration profile at the interfaces, the new model determined the diffusion coefficients of boron in the phases formed at the surface of the substrates, included the diffusion zone for both steels.
30 citations
TL;DR: In this paper, the surface topography of a real lotus leaf was successfully replicated using a capillarity directed soft lithographic technique, which was carried out on poly(methyl methacrylate) (PMMA) film coated on a silicon wafer.
Abstract: The surface topography of a real lotus leaf was successfully replicated using a capillarity directed soft lithographic technique. The replication was carried out on poly(methyl methacrylate) (PMMA) film coated on a silicon wafer. The friction property of the patterned surfaces was investigated on a microscale. Its friction coefficient was almost six times lower than that of the PMMA thin film. The reduced real area of contact projected by the patterned surface appears to be the main reason for its superior friction property.
29 citations
TL;DR: In this article, the growth of anodic coatings on titanium, important due to their biocompatibility and potential use in dental and orthopaedic implants, is investigated at a fundamental level.
Abstract: Plasma electrolytic oxidation (PEO) is a unique coating technology, which enables fabrication of high performance ceramic surfaces on the light metals, with thickness, topography, composition and structure controllable by the process parameters. Here the growth of anodic coatings on titanium, important due to their biocompatibility and potential use in dental and orthopaedic implants, is investigated at a fundamental level. The work has achieved major impact in understanding coating growth from original tracer studies. For the first time discrete thickening at sites of dielectric breakdown, local growth at the metal/oxide interface and destruction of earlier formed oxide were shown, which offered a new perspective on coating processes, including those aspects affecting coating efficiency – a critical feature in a relatively high cost technology. Furthermore, based on the fundamental findings, routes to tailored coating compositions for enhanced biocompatibility have been developed, and carried th...
TL;DR: In this paper, experiments for determining the adhesion properties have been performed using two test methods; tensile adhesive test which is widely used in industry and interfacial indentation test still under development in research laboratories.
Abstract: In this paper, experiments for determining the adhesion properties have been performed using two test methods; tensile adhesive test which is widely used in industry and interfacial indentation test still under development in research laboratories. Therefore, only few experimental data on the accuracy of the methods and on the potential in an industrial context are available. For that reason, dissimilar coating–substrate combinations covering different ranges of type of thermal spray coating–substrate systems were tested. Ceramic (Al2O3) and metallic (80Ni–20Cr) coatings were deposited by flame spraying system with two different thicknesses on titanium alloy and steel substrates exhibiting each two distinct roughness levels. The distinguished coating properties include the interfacial toughness and adhesive strength. The impacts of interfacial roughness and the thickness of the coating on the adhesion were conducted, and some adhesion tendency was also observed. Typical bond strength values measur...
TL;DR: In this paper, the electrochromic properties of electron beam evaporated tungsten oxide (WO3) thin films at different electrolytes were investigated and the authors observed the better electro chromic performance for the as deposited room temperature prepared films than the higher substrate temperature prepared and annealed films.
Abstract: In the present paper, the authors report on the electrochromic properties of electron beam evaporated tungsten oxide (WO3) thin films at different electrolytes. The authors observe the better electrochromic performance for the as deposited room temperature prepared films than the higher substrate temperature prepared films and annealed films. In addition, the less reversible coloration was observed for the heavier ion (K+) intercalation/deintercalation than the lighter one (Li+), which may be due to the effect of microstructure of the films, and ion mobility. The possible role of electrochromic performance in the mechanism of film crystallinity has been discussed.
TL;DR: In this article, thin films of TiAlN were deposited on (111) oriented silicon single crystal substrates from a composite Ti-Al target by DC reactive magnetron sputtering at 773 K under various N2 flow rates.
Abstract: Thin films of TiAlN were deposited on (111) oriented silicon single crystal substrates from a composite Ti–Al target by DC reactive magnetron sputtering at 773 K under various N2 flow rates. Substantial influence of N2 flow rate on the rate of deposition, grain size, crystallinity, composition, hardness and resistivity was observed. While the deposition rate, grain size and the ratio of concentration of Ti to Al of the deposited TiAlN films decreased with increasing N2 flow rate, the resistivity of the films increased with increasing N2 flow rate.
TL;DR: In this article, the surface of AISI-T1 samples was scanned by a laser beam with varying laser treatment conditions (laser power and scanning speed) and an investigated laser treatment condition promising good characteristics was chosen and applied on T1 peeling tool edges, then its wear resistance was tested for peeling beech wood.
Abstract: For many wood machining processes, the interest of tool steels remains very important because of their good tool edge accuracy and easy grinding. The main problem is their low resistance to wearing and moderately toughness. To increase their performance, a laser treatment applied on the tool edges was presented in this paper. First, the surface of AISI-T1 samples was scanned by a laser beam with varying laser treatment conditions (laser power and scanning speed). Second, an investigated laser treatment condition promising good characteristics (high hardness, high melt volume, no cracks) was chosen and applied on T1 peeling tool edges, then its wear resistance was tested for peeling beech wood. The experimental results show that the microhardness of the melted T1 samples was affected by the laser power and the scanning speed. The microhardness was slightly increased with increasing laser power and with decreasing scanning speed. The microhardness of the melted T1 samples under each treatment condit...
TL;DR: In this article, the authors present an investigation that demonstrates that developments in nitriding have been driven by the need to address environmental concerns, and reduce both energy consumption and process time.
Abstract: Over the years, developments in nitriding have been driven by the need to address environmental concerns, and reduce both energy consumption and process time. The present investigation demonstrates...
TL;DR: In this paper, the role of surface modifications produced by different levels of polishing on the indentation hardness of stainless steel was examined. And the Vickers hardness of four stainless steel samples, three polished and one ground were measured in the micro- (0·1−10 N load) and macro-hardness (10−2500 N load).
Abstract: When measuring the indentation hardness of a material, the hardness number is generally not constant in the micro- and nano-hardness ranges but varies with the applied load. In the present work, we examine the role of surface modifications produced by different levels of polishing on this load dependence. The Vickers hardness of four stainless steel samples, three polished and one ground were measured in the micro- (0·1–10 N load) and macro-hardness (10–2500 N load) ranges. At loads exceeding ∼10 N, a constant, low bulk hardness that is the same for all polished samples, is found. We also find that each of the four methods of surface preparation leads to different rates of increase in microhardness with decreasing load. Although this pattern of hardness change is consistent with real variations of microhardness with depth, we examine various models that have been used to describe the indentation size effect to interpret and model the measurements. We note that most of the existing models can be f...
TL;DR: Laser transformation hardening in the solid state is shown to successfully provide a surface hardness increase of almost 40% for Ti-6Al-4V with a case depth over 2.5 mm while reducing surface damag...
Abstract: Laser transformation hardening in the solid state is shown to successfully provide a surface hardness increase of almost 40% for Ti–6Al–4V with a case depth over 2.5 mm while reducing surface damag...
TL;DR: In this article, a finite element method (FEM) simulation based on the orthogonal experimental design is adopted to analyse the interaction of different shock pressure profiles with the material.
Abstract: Laser shock processing (LSP) is a competitive alternative surface enhancement process. Shock pressure with high magnitude and short duration induced by LSP is one key parameter to induce a residual stress field in the material. Finite element method (FEM) simulation based on the orthogonal experimental design is adopted to analyse the interaction of different shock pressure profiles with the material. It can give a relatively accurate description of the effect of shock pressure profile on the residual stress field induced in the material with a representative coverage of all parameters by less calculation cost. The analysis results show that laser shock conditions should be selected carefully to ensure a favourable shock pressure to obtain an optimised residual stress field. The simulation on the overlapping laser shock is also presented and indicates that it is an effective method to settle the residual stress drop on the top surface and can obtain a much more favourable residual compressive stress field to enhance the fatigue resistance of the material.
TL;DR: In this paper, a type 316L stainless steel rod was coated with 300 μm yttria stabilised zirconia (≈8%Y2O3) by plasma spraying over a 50 μm metallic bond coating of NiCrAlY.
Abstract: Type 316L stainless steel rod was coated with 300 μm thick yttria stabilised zirconia (≈8%Y2O3) by plasma spraying over a 50 μm metallic bond coating of NiCrAlY. However, the presence of porosity and microcracks in the as sprayed coating is a drawback. In the present work an attempt was made to study the plasma spraying of such coatings and to enhance their properties through laser surface treatment. A continuous wave CO2 laser of 10·6 μm wavelength with a beam diameter of 1·5 mm was used to eliminate porosity and microcracks. Powers of 50, 75 and 100 W with 2500 μm s&minus1 scan rate and 500 μm step size were applied to melt the surface. The as coated and laser treated samples were characterised using X-ray diffraction, optical microscopy and SEM. The porosity was decreased from 10% in the as coated sample to 0·5% in the laser treated samples. Segmented cracks were formed due to residual stresses developed during laser remelting and solidification. Delamination occured near the bond coat/ceramic ...
TL;DR: In this paper, the laser heat treated surfaces were characterised for their microstructure using optical and scanning electron microscopy which revealed different levels of martensitic transformation based on the scan speed employed in processing the samples.
Abstract: High power diode laser hardening of steels, namely AISI 1018l AISI 4140 and grey cast iron has been carried out at a power level of 4 kW. A rectangular laser beam of 13 × 4 mm was used for hardening at scan speeds of 1000, 1500 and 2000 mm min−1. The laser heat treated surfaces were characterised for their microstructure using optical and scanning electron microscopy which revealed different levels of martensitic transformation based on the scan speed employed in processing the samples. The microhardness profile of the heat treated region revealed much higher hardness values as compared with that of base metal. The wear resistance of the laser heat treated samples was evaluated in the pin on disc machine as per ASTM standard G-99A at a constant load of 10 kg and a sliding speed of 5 m s−1. The results indicated highest wear resistance for sample processed at 1000 mm min−1 in the case of AISI 1018 steel, while in the case of AISI 4140 steel and cast iron, the sample processed at 2000 and 1500 mm mi...
TL;DR: In this paper, the appearance evolution of microdischarges, the phase composition and the morphology transition of the coating formed by plasma electrolytic oxidation on AZ91D magnesium alloy were studied. And the diameter of micropores together with netlike fine microcracks increased when the higher voltage was employed.
Abstract: The present paper studied the appearance evolution of microdischarges, the phase composition and the morphology transition of the coating formed by plasma electrolytic oxidation on AZ91D magnesium alloy. The appearance of microdischarges population experienced apparent changes in size, spatial density and colour, which related with the changes of the type and quantity of the disintegrated gas bubbles generated in the interface between the electrolyte and substrate. Correspondingly, the diameter of micropores together with netlike fine microcracks increased when the higher voltage was employed. The coating composed of MgO, MgAl2O4 and there existed a fluoride enriched zone of about 1–2 m m at the film/substrate interface, which may be closely related with the decomposition of the hexafluorinealuminate ion and the initiation, damping of the microdischarges.
TL;DR: In this paper, two different coatings of 1100 aluminium were cold sprayed onto similar substrates, using He and 20N2 (vol.-%) mixture as carrier gases, and three point bend testing was carried out.
Abstract: Two different coatings of 1100 aluminium were cold sprayed onto similar substrates, using He and He–20N2 (vol.-%) mixture as carrier gases. Three point bend testing was carried out. The elastic moduli of the coatings were found to be close to each other and the substrate. The He processed coating showed higher fracture strength which was attributed to the higher degree of strain hardening. The He–20N2 processed coating failed at lower stress owing to its strain relaxed structure. The mode 1 fracture of the coating substrate system was found to be higher for the helium processed coating. The toughness was correlated to the microstructure. The delaminated coating showed a higher degree of brittle failure of the interface for the He processed coating.
TL;DR: In this paper, a TiC reinforced composite layer is formed when the composition is 75TiC-25Ni (wt-%) and laser power 2·5 kW and scan speed 0·2 m min−1.
Abstract: Al–Si alloy was laser surface treated with various compositions of TiC and Ni under different laser processing parameters to produce a TiC reinforced composite layer on it. The study shows that TiC composite layer is formed when the composition is 75TiC–25Ni (wt-%) and laser power 2·5 kW and scan speed 0·2 m min−1. The layer exhibited an average microhardness of ∼750 HV, which is free from pores as well as cracks and contained TiC and Al–Si phases distributed in the Ni–Al matrix. Mechanical strength of layer is studied by the hardness test.
TL;DR: In this article, the wear properties of Al2O3 bearing coatings, produced by in situ laser induced thermite reactions fabricated on aluminium alloy 7075, were examined and the results of the XRD and XPS analyses showed that in all the three reaction systems, a reaction layer which comprised mainly Al 2O3 and Al phases was formed.
Abstract: The wear properties of Al2O3 bearing coatings, produced by in situ laser induced thermite reactions fabricated on aluminium alloy 7075, were examined. The thermite reactions were initiated by the laser cladding of mixed powders of CuO–Al, Cr2O3–Al and TiO2–Al. In order to improve the quality of the laser formed coatings, the laser cladding involved two passes of melting. The results of the XRD and XPS analyses showed that in all the three reaction systems, a reaction layer which comprised mainly Al2O3 and Al phases was formed. Under dry sliding conditions, the wear resistance, in terms of weight loss, of the laser cladded specimens was considerably higher than that of the uncladded specimens. The predominant wear mechanism of the former specimens was found to be characterised by abrasive, while with the latter specimens, it was the adhesive wear that prevailed.
TL;DR: In this article, the influence of oxygen cold plasma parameters on the wettability of polypropylene surfaces treated was evaluated and the aging time was also assessed, which represents a fundamental step to plan the insertion of the plasma process inside an industrial system.
Abstract: Polypropylene is one of the most versatile polymers. The wide range of physical properties and relative ease of processing make it an extremely attractive material capable of competing with more expensive resins in a number of demanding applications. Its key limitation is its poor adhesion towards paints. The low polarity of the molecules in polypropylene is the cause of the low surface energy of these plastics. Increasing the surface energy is one of the major purposes of pretreatment for such plastics. The cold plasma process represents a more efficient, cleaner and cheaper treatment than the flaming traditional treatment to activate polypropylene surfaces. The aim of this work has been to evaluate the influence of oxygen cold plasma parameters on wettability of polypropylene surfaces treated. The wettability aging time has been also assessed because it represents a fundamental step to plan the insertion of the plasma process inside an industrial system. A set of process variables (voltage, time...
TL;DR: In this article, the multilayer coatings consisting of Ni-P, ZrO2 and electroplating Ni coatings were investigated and the microstructures were analyzed by XRD.
Abstract: The multilayer coatings consisting of electroless Ni-P, Ni-P-ZrO2 and electroplating Ni coatings were investigated. The surface and cross-section morphologies of coatings were observed with SEM. The microstructures were analysed by XRD. The corrosion resistance was evaluated by potentiodynamic polarisation curves and salt spray tests. The results showed that the electroplating Ni coating was crystal structure, whereas the electroless Ni-P and Ni-P-ZrO2 coatings displayed amorphous characteristic. The electroplating Ni coating exhibited more positive corrosion potential E-corr and lower corrosion current density l(corr) than that of electroless Ni-P and Ni-P-ZrO2 coatings. The samples covered with multilayer coatings of Ni-P-ZrO2/Ni/Ni-P (from substrate to surface) indicated the best corrosion resistance among six samples, and the salt spray tests were carried out for more than 1000 h. According to the analysis of corrosion mechanism, the upper Ni-P layer served as sacrificial protection anode due to its more negative corrosion potential E-corr in comparison with the middle electroplating Ni layer. When the upper Ni-P layer was consumed, the middle Ni layer went to prevent from corroding. Until the corrosion pits penetrated all of the protective coatings, the substrate of magnesium alloys was destroyed completely.
TL;DR: In this paper, laser processed Cr-SiC coatings were produced on AISI type 316L stainless steel substrate using a continuous wave CO2 laser and the microstructure of the laser processed coatings consists of planar growth at the interface, followed by columnar dendrite and fine cellular structures at the core and top surface of the molten zone.
Abstract: Laser processed Cr–SiC coatings were produced on AISI type 316L stainless steel substrate using a continuous wave CO2 laser. The microstructure of the laser processed coatings consists of planar growth at the interface, followed by columnar dendrite and fine cellular structures at the core and top surface of the molten zone. High temperature phases such as δ-ferrite, γ-austenite and M7C3 carbides were found in the resolidified microstructure. The microchemical analysis of the laser processed zone showed the presence of high concentration of silicon. The laser processed zone also exhibited high hardness around 1300 HV.
TL;DR: In this article, the basic mechanical properties of PVD hard coatings, which are currently used in Koncar Alati company for wear protection of forming tools manufactured on request of the Electrolux Group, with emphasis on Denmark A/S, have been compared.
Abstract: In the present paper the basic mechanical properties of PVD hard coatings, which are currently used in Koncar Alati company for wear protection of forming tools manufactured on request of the Electrolux Group, with emphasis on the Electrolux Home Products company, Denmark A/S, have been compared. This company has high demands on tool performance for machining and forming of several different workpiece materials, such as sheet steel, stainless steel, aluminium and Teflon coated sheet. Two different deposition methods were used for preparation of hard coatings: sputtering using unballanced magnetron sources - CC800 (CemeCon) and cathode arc evaporation [BAI 1200 (Balzers)]. The coatings for test were deposited on four different tool steels. It was found that the hard coatings investigated in the present work showed a wide range of mechanical properties: microhardness in the range of 900-3200 HV, critical load for total delamination in the range of 75-135 N, indentation modulus in the range of 120-390 GPa and the scratching coefficient in the range of 0m ; ; 02-0m ; ; 09.
TL;DR: In this paper, the influence of post-spray heat treatment on microstructure, microhardness and abrasive wear behaviour of flame sprayed stellite (EWAC 1006 EE) coatings deposited on mild steel has been reported.
Abstract: In the present paper, the influence of the post-spray heat treatment on microstructure, microhardness and abrasive wear behaviour of flame sprayed stellite (EWAC 1006 EE) coatings deposited on mild steel has been reported. Coatings were deposited by oxyacetylene flame spraying torch. The post-spray heat treatment of the coatings was carried out at 800°C for 2 h. Wear behaviour of coatings was evaluated using pin on plate wear system against SiC abrasive medium of 120 and 600 grade at 5, 10, 15 and 20 N normal load. It has been found that the influence of normal load on wear behaviour of these coating is governed by the microstructure, hardness and abrasive grit size. Heat treatment decreases average microhardness of the coating. Heat treatment improved the abrasive wear resistance against fine grit size abrasive medium, while it deteriorated wear resistance against coarse abrasive. Scanning electron microscopy (SEM) study indicates that the wear is largely governed by groove formation, microcutti...