In-situ synthesis of a carbide reinforced steel matrix surface nanocomposite by laser melt injection technology and subsequent heat treatment

The concept of in-situ synthesis of composites by laser melt injection technology is introduced, dictated by the minimum size requirement for particles being able to incorporate into liquid metals. The mixture of relatively large Ti and WC particles are blown into the laser melted pool of a low-alloyed steel substrate. Macroscopically, the 1-mm thick melted layer appears to be homogeneous, due to the strong Marangoni convection. Sub-micron-sized (Ti, W)C primary particles are precipitated from liquid steel upon fast cooling and solidification. Upon heat treatment a large number of nano-sized (Fe,W)6C particles precipitated from the oversaturated steel matrix. The microhardness of the composite layer is considerably higher compared to that of the initial steel matrix.