Investigations include FEM simulation model of alloying the PMHSS6-5-3 steel surface layer with the carbides and ceramic powders, especially WC, VC, TiC, SiC, Si3N4 and Al2O3 particles using the high ...power diode laser (HPDL). The FEM computations were performed using ANSYS software. The scope of FEM simulation was determination of temperature distribution during laser alloying process at various process configurations regarding laser beam power and method of powder deposition, as pre coated past or surface with machined grooves. The FEM simulation allows specifying the heat affected zone and the temperature distribution in the sample as a function of time and thus allows the estimation of the structural changes taking place during laser alloying process.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Growth morphology transitions of austenite during solidification of a laser remelted Fe–C–Si alloy have been studied by theoretical modeling and laser remelting experiments. A synthetic cast iron ...with 1.7
wt% C and 4.3
wt% Si was remelted using laser scanning velocities ranging from 5×10
−5 to 2×10
−1
m/s. Three different austenite morphologies have been found: planar, cellular and dendritic. A transition from planar to cellular solid/liquid interface of the austenite crystals is observed at a solidification velocity of 30
μm/s. Another morphological transition between cells and dendrites is observed at 1.5
mm/s growth velocity. The experimental results of transition velocities have shown good agreement with theoretical values. The primary dendrite spacing in the laser remelted zone is also evaluated and compared with the theoretical predictions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In der Oberfläche von monolithischer Aluminiumoxidkeramik wurden durch lasergestütztes Umschmelzen und Zugabe von Hafniumoxid (HfO2), Wolfram (W), oder einer Mischung von Zirkonoxid (ZrO2), ...Wolframkarbid (WC) und Titannitrid (TiN) mehrphasige Gefüge eingestellt. Mit Hilfe der Rastersondenmikroskopie wurden Eigenschaften und das tribologische Verhalten verschiedener zweiter Phasen der mehrphasigen Al2O3‐Keramiken in Kontakt mit Si‐Spitzen auf der Mikro‐/Nanoskala untersucht. Aus den mikrotribologischen Ergebnissen zur Reibungszahl, Einsprungkraft und Abrisskraft in Abhängigkeit von der Luftfeuchte wurden Folgerungen für die tribologischen Wirkmechanismen einzelner Phasen abgeleitet. Es zeigte sich ein starker Einfluss von weichen Oberflächenfilmen auf die mikrotribologischen Wechselwirkungen.
Investigation of Microtribological Properties on the Micro‐Scale of Multiphase Oxide Ceramics by Scanning Probe Microscopy
Multiphase microstructures were obtained in the surface of monolithic alumina ceramic by laser‐remelting and addition of Hafnium oxide (HfO2), tungsten (W), or a mixture of zirconium oxide (ZrO2), tungsten carbide (WC) and titanium nitride (TiN). Properties and tribological behaviour of different second phases of the multiphase Al2O3 ceramics were investigated on the micro‐/nanoscale in contact with Si‐tips by using scanning probe microscopy. From the microtribological results concerning friction coefficient, jump‐in force, and pull‐off force as function of rel. humidity of the surrounding air, conclusions were derived about the effects of the different phases of the ceramics. A strong effect on the interaction between the Si‐cantilever tip and the phases was caused owing to soft surface films.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This paper shows a theoretical and experimental study of the CO2 laser remelting of plasma sprayed coatings. The aim of the process is the decrease of the porosity to improve the layer properties. In ...a first approach simulation helps in finding the right process parameters, those parameters allow the melting of the sprayed layer and a minimal amount of substrate material to minimize dilution. The presented modelling includes several features allowing the description of phase transition in the remelting process, the main point is the use of different absorption coefficient in the two phases. Monitoring results gave additional information about the process and another way of doing process validation. The main result are is the prediction size and shape of the remelted layers and due to that the simulation code can be used in the parameter finding and plays an important role in the complete understanding of the process.
Este artículo describe un estudio teórico y experimental del proceso de refusión, por láser de CO2, de recubrimientos depositados por plasma. Se trata de lograr mediante el proceso de refusión una buena unión metalúrgica entre recubrimiento y sustrato, entre las diferentes partículas que componen el recubrimiento y de este modo evitar que el recubrimiento sea frágil y tenga una baja adherencia con el sustrato. En una primera aproximación la modelización sirvió de ayuda para lograr los parámetros adecuados que permitiesen fundir toda la capa proyectada junto con una mínima porción del sustrato para minimizar el grado de dilución. La modelización presentada incluye algunos aspectos que ayudan a describir el cambio de fase asociado a la refusión, estos son la utilización de las propiedades termofísicas adecuadas y la variación del coeficiente de absorción en el paso de la fase sólida a la fundida. Los resultados de la monitorización refuerzan el conocimiento del proceso y ayudan a la validación del modelo. Los resultados consisten en la predicción, con bastante precisión, de la forma y tamaño de las regiones fundidas para diferentes condiciones del proceso, lo que permite realizar el estudio paramétrico con la ayuda del computador, minimizando pruebas experimentales.
Laser remelting experiments at 50 and 100 μm/s scanning velocity were employed to study the microstructure in Fe-C-Si alloys with compositions in the range: 3.2-4.2 wt.%C and 1-3 wt.%Si. Due to the ...geometry of the liquid pool, different growth velocities were obtained during remelting; zero at the bottom of the pool and a rate close to the laser velocity near the surface. Solidification starts with gray iron with vermicular graphite morphology and changes to a white ledeburitic structure near the surface. The measured velocity for the gray-white transition was about 43 μm/s for all analyzed alloys. Theoretical models show that this transition velocity is highly sensitive to the Si-content in the alloy, which was not verified by the experiments. Changes in composition of C and Si during processing explain the observed disagreement between experimental results and theory.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
NiCoCrAlY clad coating on the GH140 alloy surface was remelted by laser. The studies show that selecting proper laser remelting parameters can refine the structure in the remelted zone, increase the ...density of coating, strengthen the interfacial bonding and, moreover, hardly dilute the alloying elements in the laser remelting zone. As a result, the resistance of the coating against the corrosion and thermal cycles is significantly increased. Also, the good plasticity of the original coating remains.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Purpose: Results of laser treatment at cryogenic conditions and its influence on microstructure, microhardnessand properties of the SUPERSTON alloy are presented in this ...article.Design/methodology/approach: New method of the laser remelting specimens diped in liquid nitrogen madeby the CO2 laser with 6000W laser beam power and scanning velocity 1.0 m/min was employed. Observationmicrostructure was carried out by scanning electron microscope. Hardness of cross-section of the surface layerhas been measured by the Vickers microhardness under load 0.49 N. Corrosion investigation in 3% NaCl by theAtlas 9131 equipment conected with computer PC was done.Findings: Laser remelting lets obtain fine microstructure in surface layer and increase of microhardness andcorrosion properties, compared with base material.Research limitations/implications: The future investigations connected with aplication conditions should beextend of cavitation tests in the magnetostriction stand.Practical implications: Obtained results point at possibility of the increase hardness, corrosion and cavitationresistance of the parts worked in marine conditions.Originality/value: The proposed laser treatment at cryogenic conditions could be used for surface consolidationof the copper alloys applied for ship propellers.
We consider a model for laser surface remelting, a process to improve the surface quality of steel components. The mathematical model consists of the two-dimensional heat equation for temperature and ...an ordinary differential equation for the liquid phase. The equations are coupled via source terms. We study the efficient numerical simulation using adaptive grids, which are especially well-suited for problems with moving heat sources. To account for the local high activity due to the heat source, we introduce local uniform grids and couple the solutions on the global coarse and local fine grids using the local defect correction (LDC) technique.
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