Microstructure evolution of phase separated Fe-Cu-Cr-C composite coatings by laser induction hybrid cladding

To investigate the cooling rate on the microstructure evolution of phase separated Fe-Cu composite coatings by laser induction hybrid cladding (LIHC), the different laser scanning speed is adopted to estimate the temperature profiles and cooling rate of the molten pool. When the low laser scanning speed is adopted during LIHC, the Cu-rich spherical particles are embedded dispersedly in the Fe-rich interdendrites at the bottom of coating, while the nanostructured Fe-rich dendrites and the Fe-rich particles are distributed simultaneously in the Cu-rich matrix at the top of coatings. However, the increasing of laser scanning speed can decrease the temperature of the molten pool and increase the cooling rate of the molten pool. This in turn leads to an increase in dynamic supercooling and solute trapping of Cu in the enhanced Fe-rich dendritic refinement, but a decrease in size of Fe- and Cu-rich particles as well as a reduction in size of nanostructured Cu-rich grains inside the Fe-rich particles due to the secondary liquid phase separation.