PHASE INVESTIGATION IN LASER-SURFACE ALLOYED STEELS WITH TIC

Laser technology enables melting and alloying specimen surfaces withou t the substrate itself being heated, whereby surfaces with special att ributes are obtained with the properties of the substrate remaining un affected. The surfaces of Armco iron and AISI 1045 steel were laser-al loyed 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 composit e material, steel+TiC. The microstructures were investigated metallogr aphically. Some of the particles had partially melted during their pas sage through the laser beam and had re-solidified, forming small and f ine dendrites. Phase identification by X-ray diffraction revealed the presence of alpha-Fe, martensite, and Fe3C phases, as well as amounts of stochiometric TiC and unknown phases. Identification of phases by T EM and diffraction of electrons revealed the presence of unknown phase s, such as tetragonal TiC and (FeTi)C. Mossbauer 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.