HVOF Process Control Enabling Strategies

Complexity in dynamics of super sonic flame formation mechanisms and effects of processing variables has made the understanding of interaction of particles and flame a difficult task. Lack of such understanding limits the possibilities of controlling the process to obtain desired in-flight particles temperature and velocity and consequent particles state. This problem is even more pronounced in TS systems with no dedicated decoupled temperature and velocity controlled regime. Different approaches based on total volume flow, back pressure and fuel to oxygen ratio have been examined to address the robustness of each approach to control the temperature and velocity. WC-CoCr material was used employing DJ-2600 torch. A guideline to control the in-flight particles temperature and velocity based on process variables is provided. Further, particles state was presented based on non-dimensional group parameters, melting index and kinetic energy, and microstructure of deposited coatings was addressed by recourse to these parameters.