Atom-scale characterization and 2D/3D modeling of carbides and Fe-Co phases in Stellite 6 laser clad coating after aging treatment

This study applied various aging treatment (AT) times at 650 degrees C in Stellite 6 laser cladding layer, conducted the atom-scale characterization of stacking faults (SFs) and nanoscale M23C6 carbides, described the martensitic transformation of gamma -> epsilon, and discussed on the growth mechanism of Fe-Co and M23C6 phases by 3D/2D modeling. Results show the formation of three distinct regions relative to Fe diffusion, namely, interfacial layer with Fe-Co and M23C6 phases, Fe diffusion-affected zone with FexCoy distribution at the edge of M23C6 carbides along grain boundary, and Fe diffusion-unaffected zone with abundant carbide precipitation and SF generation. In addition, the formation of M23C6 and Fe-Co phases conformed to dynamics and thermodynamics. Suzuki effect influence the nanoscale carbides with profile and growing direction of [121] and [110], respectively, and martensite transformation occurred on (111)gamma parallel to (0002)epsilon as characterized by 2D modeling and HRTEM. The microhardness of surfacing layer was measured in diverse zones, and the results present that AT softened the interfacial layers but increased the hardness of Fe diffusion-affected zones and Fe diffusion-unaffected zones.