Fabrication of conventional and nanostructured NiCrC coatings via HVAF technique

摘要

The conventional and nanostructured NiCrC(with chemical composition of 80%NiCr-20%CrC)coatings with high quality were fabricated via high velocity air-fuel(HVAF)spraying technique.The microstructures of these coatings were characterized by means of metallographic microscopy,scanning electron microscopy,transmission electron microscopy and X-ray diffractometry.A Vickers microhardness tester was used to determine the mechanical properties of the as-sprayed coatings.The single-line approximation(SLA)method was employed to calculate the grain size and microstrain of as-sprayed nanostructured coating based on the XRD data.The results show that nanostructured NiCrC coating possesses a more uniform and denser microstructure,much higher microhardness and better fracture toughness than its conventional counterpart.Both TEM observation and calculation results based on XRD profile show that as-sprayed nanostructured NiCrC coating has a homogeneous nanocrystalline microstructure with an average grain size of 40 nm.