Paper present a thermal analysis of laser heating and remelting of EN AC-48000 (EN AC-AlSi12CuNiMg) cast alloy used mainly for casting pistons of internal combustion engines. Laser optics were arranged such that the impingement spot size on the material was a circular with beam radius rb changes from 7 to 1500 μm. The laser surface remelting was performed under argon flow. The resulting temperature distribution, cooling rate distribution, temperature gradients and the depth of remelting are related to the laser power density and scanning velocity. The formation of microstructure during solidification after laser surface remelting of tested alloy was explained. Laser treatment of alloy tests were perform by changing the three parameters: the power of the laser beam, radius and crystallization rate. The laser surface remelting needs the selection such selection of the parameters, which leads to a significant disintegration of the structure. This method is able to increase surface hardness, for example in layered castings used for pistons in automotive engines.
The laser surface remelting of Ti-6Al-4V titanium alloy without coat was carried out in order to determinate its microstructure. Laser alloying was performed on samples, coated by graphite powders in order to form titanium carbides as a consequence of laser pulsed irradiation. Alloyed layers containing TiC phase in ductile martensitic matrix exhibit high microhardness (about 6 GPa), excellent bonding with the substrate and are free of cracks.
PL
Przeprowadzono laserowe przetopienie powierzchni stopu tytanu Ti-6Al-4V przy użyciu lasera impulsowego. Stosowano próbki z pokryciem grafitowym oraz bez pokrycia. Obserwowano zmiany mikrostruktury stopu w warstwie przetopienia i strefie wpływu ciepła. Stwierdzono wzrost mikrotwardości (do około 6 GPa) modyfikowanych laserowo warstw wierzchnich.
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