High-temperature alloys such as IN718 are widely used in gas turbine components as they remain stable at operating temperatures up to 1100 °C. There is now a growing interest in the repair and refurbishment of such components using spray deposition techniques.
Although many investigations have been carried out to study the effect of conventional processing on the microstructure and mechanical properties of IN 718, much less attention has been given to the alloy when sprayed to form a coating. The purpose of the present study was to investigate and compare IN 718 deposits produced by HVOF spraying and cold gas spray deposition.
Optical microscopy, scanning electron microscopy and X-ray diffraction were employed to examine the microstructural evolution of the coatings and to compare the deposition behaviours of the two different processes.  Particular attention was paid to porosity, oxide content and the formation of secondary intermetallic phases. Coating microhardness and bond strength were also measured. Results will be presented and discussed in the context of the different thermal histories of powder particles in the two processes.