Phase investigation in laser surface alloyed steels with TiC

Abstract

Laser technology enables melting and alloying specimen surfaces without the substrate itself being heated, whereby surfaces with special attributes are obtained with the properties of the substrate remaining unaffected. The surfaces of Armco iron and AISI 1045 steel were laser-alloyed with TiC powder, a CO₂ laser of 2.5 kW maximum power being used. Optimal laser and powder-feed parameters were established. Particles of TiC were injected into the molten surface layer, forming a composite material, steel + TiC. The microstructures were investigated metallographically. Some of the particles had partially melted during their passage through the laser beam and had re-solidified, forming small and fine dendrites. Phase identification by X-ray diffraction revealed the presence of α-Fe, martensite, and Fe₃C phases, as well as amounts of stochiometric TiC and unknown phases. Identification of phases by TEM and diffraction of electrons revealed the presence of unknown phases, such as tetragonal TiC and (FeTi)C. Mössbauer results show ternary Fe-Ti-C phases, which can be related to the TEM and X-ray diffraction results. A correlation was found between the substrate's composition, microstructures, and the different phases present.