in-situ synthesis of titanium carbide particles in an iron matrix during diode-laser surface alloying of ductile cast iron

An in-situ formation of titanium carbide (TiC) particles in an iron matrix during diode-laser surface alloying of ductile cast iron (DCI) with direct injection of titanium powder into a molten pool was investigated. The microstructure of the in-situ TiC-reinforced surface alloying layers (SALs) was assessed with scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Comparative erosion tests of the as-received DCI and the SALs were performed following the ASTM G 76 standard test method. It was found that the morphology and volume fraction of the TiC particles directly depend on the amount of the titanium powder introduced into the molten pool, which, in turn, is strongly affected by the laser-power level. An increase in the titanium concentration in the molten pool results in a change in the TiC morphology, form cubic (> 2 μm in size) to dendritic (up to 10 μm in size). The maximum volume fraction of the TiC particles in the SALs was 12 %. The SALs exhibited a noticeable increase in the erosion resistance in comparison to the as-received DCI, especially at steep angles.