Microstructure and properties of graphene reinforced co-based composite coating by laser cladding

Graphene (Gr)-reinforced Co-based (Co50) composite coatings were prepared on 40Cr steel substrates by laser cladding technology. The effects of different amounts of Gr addition on the microstructure and mechanical properties of the coating were studied. The addition of a proper amount of Gr can improve the comprehensive properties of the coating, and most of the Gr forms carbides, such as Cr23C6 and Cr7C3, under the action of laser irradiation. The addition of Gr can significantly refine the grains and evenly distribute them. When the addition of Gr is 3 wt%, the average grain size in the coating is the smallest, which is 5.7 mu m, and the highest microhardness reaches 777.5 HV0.2, which is an increase of 270.2 % compared with that of the substrate. The unmelted Gr remains dispersed in the coating, which can improve lubrication and reduce friction. The average friction coefficient and wear volume are decreased to 0.335 and 4.26 x 107 mu m3, which are approximately 54.2 % and 28.0 % of those of the substrate, respectively.