WC-Fe metal-matrix composite coatings fabricated by laser wire cladding

Tungsten carbide reinforced iron-based metal-matrix (WC-Fe) composite coatings, for the first time, have been fabricated on carbon steel substrate by the laser wire cladding with a novel type of Fe-based tubular cored wire. The processing characteristics have been systematically investigated by cladding of single tracks at varying operating parameters. In order to guide the actual production and predict the influence of different parameters on the typical processing characteristics in terms of wire stubbing transfer, wire plunging transfer, and liquid spreading transfer mode, a process window has been established. The experimental results show that the unmelted defects can be found in the coatings produced in the stubbing transfer mode, while most of the coatings obtained in the liquid spreading transfer mode have a high dilution degree (>13 %) and a low content of retained particles (<15 %). Only the coatings fabricated in the wire plunging transfer mode possess a low dilution ratio (<13 %) and a high volume fraction of retained particles (15–26 %). The microstructural evolution in these coatings have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The ex-situ tungsten carbide particles are partially dissolved and interact with the matrix in the molten pool, resulting in the M6C (Fe3W3C) reaction layer around the retained particles. The faceted M6C carbides and the herringbone eutectic M6C carbides are found to be the primary precipitations in the coatings, combined with the presence of retained particles, the wear resistance of the WC-Fe coatings is significantly improved.