Papers by Keyword: Composite Layers

Abstract: Increasingly high expectations for modern engineering, make the constantly being sought-after new processes giving traditional materials new, better features. Nowadays, next to the classic heat treatments, advanced technologies are being used increasingly, leading to much better results than ever before. The most commonly used technologies that allow for obtaining new, enhanced properties of various metal alloys in the area of surface engineering include, among others laser surface treatment. The main objective of this paper was to analyze the influence of laser surface treatment on structural change and mechanical properties improvement of Al-Mg alloy by VC alloying. The remelted layer on the aluminium alloy surface was obtained using high power fiber laser "Ytterbium Laser System YLS-4000". The surface sample was remelted using a rectangular laser beam (2 x 4mm) with a power of 3 kW (1.53e+4w/cm²). Scanning speed of the laser beam was 0.8 cm/s (0.48 m/min). The remelting area has been protected by the use of technical argon blowing. During the process, sintered particles of vanadium carbide with an average size of about 50-100 μm was introduced into the liquid metal. Ceramic powder in the remelting volume was fed with a pressure feeder (constant rate of 5 g/min). As a substrate, the ENAC AlMg3 alloy has been used. During the laser treatment, a composite layer with much better mechanical properties was obtained comparing the base material. The average hardness of the layer was about 19 HV_0.1 higher than that of the base material. Chemical analysis, carried out with the EDS (energy dispersive spectroscopy) detector and transmission microscope revealed many undissolved powder particles used in the alloying process as well as those of Al₈V₅ precipitated in the Al-Mg matrix.

Abstract: The present work has the purpose to study and to evaluate the corrosion resistance of zinc layers and phenol – formaldehyde resin/Zn composite layers obtained by electrodeposition. For the best results it was used different parameters for electrodeposition such as: current density between 3 – 5 A/dm², time for electrodeposition: 30 minutes and 60 minutes, stirring rate: 500 rpm and 800 rpm. Different sizes (mean diameter size between 0.1 – 5.0μm and 6.0 – 10.0μm) of dispersed phases were used with concentration into electrolyte solution from 10g/L to 25 g/L of polymer particles. The morphology of the layers was investigated by SEM – EDX methods. The surface morphology of composite layers was different as compared with pure zinc layers. By adding polymer particles into zinc electrolyte during electroplating a very good distribution of polymer on zinc layer surface was obtained. The electrochemical behavior of the composite layers in the corrosive environment was investigated by polarization potentiodynamic and electrochemical impedance spectroscopy methods. As electrochemical test solution 0.5M sodium chloride was used in a three electrode open cell.

Abstract: The ferroelectric and electrical properties of potassium nitrate (KNO3): polyvinylidene fluoride (PVDF) composite layers prepared by melt press method have been studied. The stability of ferroelectric phase (phase –III) of potassium nitrate (KNO3) in the composite layers at room temperature have been analyzed. The temperature dependence of ferroelectric hysteresis loop (P-E) characteristics have been investigated in the composite layers. The electrical conductivity (σ) and dielectric behaviour of composite layers have been characterized. The conductivity and dielectric variation with temperature during heating and cooling modes has been found to provide the knowledge of phase transition in the composite. The capacitance –-voltage (C-V) and conductance - voltage (G-V) characteristics clearly show the ferroelectric butterfly loop, which is attributed to the features of ferroelectricity in the composite layers at room temperature. The coexistence of ferroelectric phase (phase III) with paraelectric phase (phase II) has also been observed at room temperature in the composite layers during dielectric and conductivity measurements.

Abstract: In the present work, laser surface alloying of H13 tool steel by using TiC has been performed by means of DHPDL (Direct high power diode laser). Different layers were produced by varying laser beam power and powder feeding rate. Several alloying degrees were obtained depending on the laser parameters employed. Laser surface alloyed layers were analyzed by using optical and scanning electron microscopy. Wear resistance was evaluated through pin-on-disk tests at room temperature. In general, it was observed that dilution of TiC powders into the molten H13 substrate decreased as the powder-feeding rate increased and particles size of the titanium carbide precipitates was larger for the higher feeding rates. Wear measurements showed lower values for the wear resistance coefficient of laser alloying layers produced at higher values of the powder injection (feeding) rate. Analysis of the wear surface track was conducted and the specific contribution of the microstructural features on the wear coefficient was assessed. Thus, it was found that larger particles sizes and particle contents protected the martensitic and dendritic steel matrix from being deeply worn. Lower TiC contents in the alloyed layer gave rise to a higher contribution of the plastic deformation in the wear track.

Abstract: The paper reports on a study regarding the structure of composite layers obtained by electrochemical deposition. The depositions were achieved in a bath formed of a mixture of aqueous solutions of iron salts (iron chloride), cobalt (cobalt sulphate) and solid particles of silicon carbide (SiC) in suspension. Following the electrochemical deposition on composite structures are formed as a thin layer with a metallic matrix (FeCo alloy), reinforced with hard particles of SiC. The structure of the composite layer is uniform and very fine, with crystalline granules under 500 nm. The electrochemically deposited FeCo alloy representing the metallic matrix of the composite layer has a high micro-hardness (864 HV), superior to the same alloy obtained by casting.

Abstract: The paper presents the results concerning the microstructure of Ti – Al intermetallic layers produced on a TA6V titanium alloy by the “duplex method”. This method combines vacuum evaporation coating of aluminum with glow discharge assisted heat treatment of the deposited films. It has been found that this combination of surface engineering techniques yields multi – layered films of the diffusive character. The films contain intermetallic phases from Ti – Al system which ensure a high microhardnes and good wear resistance. It is finally suggested that these properties can significantly widen application range of titanium alloy parts in aerospace.

Abstract: A diffusion surface layer of Ti3P+Ti-Ni type was produced on Ti6Al4V titanium alloy by a chemical electroless nickel-phosphorous deposition process combined with glow discharge treatment. The microstructure, phase composition, surface topography, corrosion and wear resistance of this surface layer were investigated, as was its biocompatibility with the human Saos-2 cell line. Cells were analysed in terms of cell viability and adhesion. The results showed that the duplex treatment permits production of a layer that has high corrosion and frictional wear resistance and the Ti3P outer zone of this composite layer is characterised by a topography and chemical composition promising high biocompatibility. This new Ti3P+Ti-Ni type layer offers new potential in biomaterials for bone applications in terms of improved tissue ingrowth and long-term use.

Abstract: A FGF-2-apatite composite layer was formed on hydroxyapatite (HAP) ceramics using supersaturated calcium phosphate solutions containing various amounts of potassium chloride. The optimum conditions for the formation of the composite layer were determined by using cytochrome C (cyt C), one of the dummy proteins of FGF-2, and an immersion solution with a Ca/P molar ratio of 0.19 and a potassium chloride concentration of 8 mM. The amounts of cyt C and FGF-2 immobilized in the composite layer were 1.28±0.30 and 3.18±0.01 µg cm-2, respectively. The release of FGF-2 from the composite layer continued for at least 3 days. It was considered that the release period of FGF-2 could be extended to day 10 because the release of cyt C continued for at least 10 days. When the composite layer is formed on commercial bone substitutes, it is expected that the promotive effect on bone formation around the bone substitutes will continue for at least 10 days.

Abstract: Fibronectin (FN)-apatite composite layers were formed on a hydroxyapatite (HAP) ceramic using supersaturated calcium phosphate (CP) solutions. The surface roughness of the composite layer could be controllable by changing the magnesium (Mg) concentration in the CP solution. The higher the Mg concentration, the smaller the apatite crystals in the layer were. The thickness of the layer formed in the CP solution containing 1.5 mM Mg decreased to 68% that formed in the Mg-free CP solution. The amount of FN immobilized in the layer was almost constant regardless of Mg concentration in the CP solution in the range from 0 to 1.5 mM. The results of the present study revealed that a thin FN-apatite composite layer with a smooth surface and a high protein content is formed in a CP solution at a Mg concentration of 1.5 mM.

Abstract: The rapid progress in engineering enhances the demands set on materials requiring better mechanical properties, resistance to frictional wear, corrosion and erosion etc. These demands can be also satisfied by e.g. applying various surface engineering techniques which permit modifying the microstructure, phase and chemical composition of the surface layers produced on the treated parts. A prospective line of the development is the production of the intermetallic layers by combining various methods aimed to improve essentially the performance properties and service life of the treated parts. The paper presents properties of the Al2O3+TiAl3+TiAl+Ti3Al type layer produced on titanium alloy Ti6Al2Cr2Mo by duplex method combined with magnetron sputtering process of aluminium coating with a glow discharge assisted treatment. The results of the examinations: microstructure, chemical and phase composition, frictional wear resistance and mechanical properties are discussed. Produced composite surface layers have the diffusion character and a precisely specified structure, chemical and phase composition and good wear and corrosion resistance what can widen significantly application range of treated parts.