The HVOF (High Velocity Oxy-Fuel) process produces low porosity, dense coatings that exhibit high bond strengths, some exceeding 12,000 PSI. It also produces low oxides and extremely fine as-sprayed finishes. The coatings have low residual internal stress and can be sprayed to a thickness not normally associated with dense, thermal sprayed coatings.
HVOF, an oxygen-fuel mixture, is fed into a combustion chamber and ignited. The expanding gases flow through a nozzle from the combustion chamber. The powder is continuously fed into the combustion chamber and exits through the nozzle onto the substrate at velocities up to 3200 feet per second.
HVOF coatings can survive harsh service conditions, particularly in wear and many corrosion applications, greatly increasing component service life. The as-sprayed, smooth surface, low porosity and uniform chemistry of the coating can be finished to very smooth surface profiles.
HVOF coatings are a common choice for dimensional restoration repair and corrosion control coatings. Many OEMs coat their new components to extend the service life. Different carbide and superalloy coatings are the primary coatings applied.
FEATURES OF THE HVOF SPRAY PROCESS
- Produces very clean, hard and dense coatings with fine homogenous structures.
- Low to compressive coating stress allows for thicker coating applications.
- Recommended for carbide coatings and often recommended for superalloy coatings.
- Low heat affected zone or component distortion.
- Surface finishes are generally smooth and can sometimes be used in the as-sprayed condition depending on the service environment.
- Coatings can be ground, machined and/or superfinished.
- Easy masking to protect areas that are not to be coated.
- Process can be fully automated utilizing robotic equipment.
- The coating of 10”+ bores are possible.