Exploring the Potential of Emerging ID-HVOF Spray Systems for the Deposition of Metallic Coatings for Part Repair and Protection

Novel internal diameter HVOF (ID-HVOF) systems enable the deposition of uniform coatings on hard-to-reach surfaces and internal diameters. By introducing an inert gas to the combustion fuels, these systems achieve warm sprayability, enabling solid and semi solid-state deposition of metal particles with minimized oxidation. Beyond protective coatings, these spray systems show promise for dimensional restoration and repair applications due to the precision of their high-resolution spray jets, allowing for targeted application of coatings. Their toolpath flexibility attributed to the compact design allows for navigation and restoration of worn areas, while minimizing the need for masking and reducing material usage. In this study, an ID-HVOF spray system with nitrogen addition was used for the deposition of Inconel and stainless-steel protective coatings on internal diameters. The deposition parameters for each material composition were systematically explored, addressing technological challenges associated with the compact design of the spray gun. By leveraging the solid and semi-solid-state deposition capabilities, optimal spray conditions were used to deposit overlays exceeding 1 mm in thickness, offering potential in repair applications. Correlations between spray parameters, inflight particle properties, microstructural characteristics, and deposit properties were established and will be discussed with comparisons to benchmark cold-sprayed counterparts as another solid-state deposition technology.