Microstructural Study of Nickle Chromium Coating with Complex Composition for High Performance Application

In this study, the HVOF spraying technology has been used to deposit NiCrSiBMoFeCuC coating. The microstructural characterization was carried out on the coating sample using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). The coating microstructure exhibited low porosity content approximately 3.17±0.93%, which is in acceptable range for an anti-corrosion protective coating. However, the SEM analysis showed some microcracks at the interfacial region between the substrate and the coating that indicates low cohesion that could be due to high temperature gradient resulting in the formation and concentration of thermal stress. Notably, a high density of dislocations within the grain core has been observed in TEM micrographs, which accounts for the increased hardness of the coating. The X-ray diffraction (XRD) analysis of the coating has identified the major peaks as expected but coating sample showed formation of some extra phases during HVOF process that may alter thermo-mechanical properties of the coating. The need for this study can be justified due to the unique composition of the coating that makes it suitable to be used as protective layer for corrosion protection in harsh environment for industrial parts and components.