Abstract :
[en] This work considers a metal matrix composite composed of 316L stainless steel and 20% in volume of tungsten carbides (WC), fabricated by laser cladding. Laser cladding is an additive manufacturing technique, characterized by ultra-fast cooling rates and limited diffusion, thus giving rise to out-of-equilibrium microstructures. The microstructure of the 316L+20%WC composite is found to consist of partially dissolved WC particles well distributed in an austenitic matrix reinforced by a network of reaction carbides. Those mixed reaction carbides are formed from a liquid enriched in W and C due to the dissolution of the original WC particles in contact with the molten metal during deposition. Distribution, chemical composition, crystallographic features and stability of the different phases in presence are characterized in details by combining SEM, EDS, EBSD and dilatometry. This combination of techniques allows to distinguish among M6C, M23C6, M4C and WC1-x carbide, belonging to the Fe-W-C system and all exhibiting a FCC lattice. Moreover, the results of reverse thermal analyses are considered together with microstructural data to elucidate the genesis of this complex microstructure, differentiating the phases formed in the melt pool, in the vicinity of the partially dissolved WC and in the heat affected zone between two successive tracks.
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