Working Principle Of High-Velocity Oxy-Fuel Coating Process (HVOF)
In this post, we’ll discuss the High-velocity Oxy-Fuel ( HVOF) Coating Processes – Principle, Working.
The high-velocity Oxy-Fuel (HVOF) coating is coming back underneath the thermal spray coating method. The thermal spraying is AN industrial coating process that consists of heat supply (flame or other) and a coating material in an exceeding powder kind. that virtually melts into small droplets and sprayed onto surfaces of the substrate at a high rate. currently, we’ll see the method very well.
Thermal Spray Coating Process:
In the thermal spraying coating method during which the coating materials are part, or all molten, either within or outside of a spray torch. The molten particles ar deposit on the surface of the substrate (base material)where the arrival droplets kind a coating.
The molten coating material droplets are deposited on the surface of the substrate while not melting it. due to this, there’s no modification in the chemical composition of the substrate.
Also, it’s determined that the moderate heat input by a thermal spray coating method can maintain the substrate material temperature rarely exceed 150°C.
When compared with alternative arduous facing welding processes, the thermal spray coating method not moving the substrate (base material) properties.
This coating method can improve the surface properties of the material like wear resistance, corrosion resistance, and erosion resistance.
Working Principle Of High-Velocity Oxy-Fuel Coating Process (HVOF)
In HVOF processes, the kinetic energy of the coating material is inflated by manufacturing high-speed gas by burning of combustion products within the combustion chamber due to the high-speed gas, the coating material can travel at supersonic speed with high-impact energy and strike the bottom material. By this principle, HVOF is going to be able to manufacture dense coatings at comparatively low temperatures.
In the HVOF coating method, K.E. a lot of necessary once compare with the temperature.
Read: Types Of Rupture Disk
Bonding Mechanisms
Due to the high K.E. and impact force for the coating particles leads to bonding effects with the substrate. ordinarily, the bonding is thanks to the adhesion, adherence, diffusion, chemical reactions, and generally partial fusion between the contact surfaces.
During the speedy hardening of the spray, particles become shut contact with the substrate surface. These bonding effects allow the formation of the endless coating layer.
HVOF working
HVOF thermal spray coating may be a continuous one. As seen from the on top of the figure, the combustion takes place within the combustion chamber at a better pressure of up to eight bars.
The various HVOF systems take issue within the style of powder injection, the look of the combustion chamber, and also the nozzle geometry. The powder feedstock is sometimes axially injecting into the recent exhaust gasses from the combustion chamber.
Usually, it’s counting on the kind of HVOF-system and nozzle system. Heating and acceleration of the particles takes place inside the nozzle of the torch, and within the free jet outside. ordinarily, the flame temperature is regarding 3000°C, and also the rate of the exiting and any increasing gasses could also be as high as 1200 m/s.
Normally the flame temperature is regarding 3000°C, and also the rate of the exiting and any increasing gasses could also be as high as 1200 m/s. The powder particles will reach velocities of up to 600 m/s, counting on the density, shape, and size of the feedstock material.
Typical for the HVOF technologies the particle moving at a speed of supersonic (Mach range >1). due to the high particle velocities, and also the moderate temperatures. This coating method is preferably used for coating materials that tend to decompose at higher temperatures.
For this reason, HVOF is widely used for the deposition of hard metals/cemented carbides like Cr carbide, Ni-Cr alloys, Co alloys and FeNiCo-alloys, i.e., Hastelloy, Stellite, Tribaloy, and self-fluxing Ni-based alloys. By HVOF coating method, uniform coating density is achieved on the surface of the substrate. thus the damage resistance of the coating is very good/high once compare with the alternative thermal spray coating method.
Application
The main field for HVOF are applications for abrasion and slippy wear. the subsequent are some example for HVOF application
- nozzles of water jet cutting tools
- rolls for paper and foil manufacturing industries,
- rolls for paper and foil manufacturing industries,
- sliding areas of pressing irons,
- valves seats,
- pumps and rotary engine shaft seal space are in petrochemical applications, and mechanical seals ar just some examples.
- Under the dynamic seal (O-ring) of the mechanical seal sleeve
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