Enhanced wear resistance of laser cladded graphene nanoplatelets reinforced Inconel 625 superalloy composite coating

An innovative and simplified method of electroless pure-nickel coating was plated on graphene nanoplatelets (GNPs). The nickel-coated graphene nanoplatelets (NiGNPs) were uniformly dispersed in Inconel 625 (IN625) powder with the ratio of 1:9 by ball milling. Then laser cladding was used to fabricate the NiGNPs reinforced IN625 composite coatings. The survivability of NiGNPs, morphology of precipitated phase, microhardness through transverse section and wear resistance at room and elevated temperatures were studied. The results indicated that the NiGNPs were successfully incorporated into IN625 coatings by laser cladding. Part of them were deduced to be damaged or dissolved into molten pool, which benefited the formation of NbC, but most of them could be observed as exposed GNPs and well-distributed welded GNPs. Compared to laser cladded IN625 coating, the composite coating showed higher hardness at bottom region of cladded coating and smaller size of HAZ due to the improvement of thermal conductivity by additional NiGNPs. Furthermore, comparative wear test demonstrated that friction coefficient (COF) and wear rate were decreased at both room and elevated temperatures. Combined with wrinkled, tiled and rolled GNPs observed on the worn surface, it was revealed that the wear properties were efficiently benefited from superior lubrication between interlayers of GNPs.