Electron microscopy and EBSD Characterization of Cold sprayed IN625 coatings on 4130 steel

Cold spray technology is being widely used in recent times, as a method of material deposition, for additive manufacturing, as well as surface enhancement, in various applications, such as corrosion, wear, in new make as well as repair and refurbishment of structural components. This study comprises a detailed electron microscopic analysis of cold sprayed Ni-based coatings (IN625 (Inconel 625 is a  Trademark of Huntington alloys corporation) and NiCr), using the transmission electron microscope and orientation imaging. The coating microstructure was analysed in the as sprayed condition, followed by a detailed characterization of the coating-substrate interface, to determine the nature of the bonding, metallurgical vs. mechanical interlocking. The thermal stability and relaxation behavior of the coatings were analysed by carrying out systematic in-situ heat treatments and mapping the diffusion kinetics along the interface. The study was able to reveal some insights about the extent of compressibility of the substrate, and via this, predict the stability of the coatings, during service.