This paper discusses the development of optimized processing windows for spraying high quality metal carbide-based coatings using advanced particle diagnostic technology. The cermet coatings are produced via the high velocity oxygen fuel spray process (HVOF) and are intended to be used in severe service applications such as marine hydraulics. To develop suitable coating process parameters, the traditional “trial and error” method is not technically robust, is costly and time consuming. Instead we investigated the use of real-time monitoring of parameters associated with the HVOF flame jets and particles using advanced in-flight particle diagnostics. Subsequently, coatings can be produced with knowledge concerning the molten particle size, temperature and velocity profile. The analytical results allow identification of optimized coating process windows, which translate to coatings of lower porosity and improved mechanical performance.