Abstract :
[en] Austenitic stainless steels are widely used due to their high corrosion resistance but their relatively poor tribological properties still limit their fields of application. The possibility of manufacturing composite coatings reinforced locally with ceramic particles has been extensively investigated and laser cladding has appeared as a technique of choice in that respect. However, when processing mixtures of metallic and ceramic powders by laser cladding, a partial or total dissolution of the ceramic particles in the molten metal is often observed, followed by the formation of new reaction products as e.g. complex precipitation carbides [1,2].
The present work proposes a slightly different approach, i.e. taking advantage of the total dissolution of silicon carbides (SiC) powder particles during laser cladding in a stainless steel 316L matrix in order to elaborate new out-of-equilibrium high-silicon austenitic stainless steels. The microstructures and local hardness of thick deposits obtained by laser cladding from a powder mixture of stainless steel 316L and respectively 10 % or 20 % in volume of SiC are characterized using SEM observations, XRD, Vickers micro-hardness and nano-indentation. DTA analyses in reverse mode (as proposed in [2]) are also considered to elucidate the solidification sequence of the new alloys. The total dissolution of the original SiC powders leads to the formation of two distinct austenitic cellular microstructures reinforced by solidification carbides with a hardness increase of 61 HV and 151 HV for additions of 10 or 20 vol. % SiC, respectively. The effect of Si enrichment in supersaturated solution in the matrix alloy composition is evaluated via nanoindentation measurements performed inside the austenitic cells. As observed in high-entropy steels, Si solid solution yields a remarkable strengthening of the FCC crystal lattice and thus contributes significantly to the improved mechanical properties.
[1] A. Mertens, “Metal matrix composites processed by laser additive manufacturing: microstructure and properties”, in Handbook in Advanced Manufacturing - Additive manufacturing, A. Riveiro, J. Pou and J. Paulo Davim (eds), Elsevier, Cambridge (2021), pp. 409-425
[2] T. Maurizi Enrici, O. Dedry, F. Boschini, J.T. Tchuindjang and A. Mertens, “Microstructural and Thermal Characterization of 316L+WC Composite Coatings obtained by Laser Cladding”, Adv. Eng. Mater. (2020), doi:10.1002/adem.202000291
