Evaluation of cold sprayed graphene nanoplates-Inconel 718 composite coatings

Graphene nanoplates (GNPs)-Inconel 718 (IN718) composite coatings were fabricated via high pressure cold spray technique with varying contents of GNPs mixed with IN718 powder. The microstructure, mechanical properties and tribological behavior of the composite coatings were systemically investigated. IN718-GNPs composite coatings could be effectively formed with the incorporation of 0.15 wt% GNPs that were uniformly distributed within the cold sprayed coatings. The deposition efficiency tended to decrease with increasing GNPs content. Following this lead, the surface roughness of the as-sprayed IN718-GNPs composite coatings was found to be related to the addition of GNPs. The surface roughness gradually increased with increasing GNPs content and the composite coating surfaces had plateau-like and crater-like features. TEM lamellae were extracted from the IN718-IN718 and IN718-GNPs interfaces of the composite coatings by focused ion beam milling. The interface between the GNPs and the IN718 matrix was clean and well bonded, illustrating a mechanical bonding. Most importantly, we found that the IN718-GNPs composite coatings provided appreciable reductions in coefficient of friction and wear rate compared to the pure IN718 coatings due to the GNPs' exfoliated surfaces and intrinsically high lubricating characteristics. Hence, the IN718-GNPs composite coatings could be excellent candidates for low friction and high wear-resistance applications.