When it comes to coating a component with hard materials such as Stellite, Chrome Oxide and Tungsten Carbide both Welding and HVOF are options. So how do the processes differ and what scenarios are each better at?
The Processes Explained
‘Welding’ is a broad term with encapsulates a number of different processes. There are many varieties of welding processes including: Arc Welding, Gas Welding, Energy Beam Welding and Solid State Welding. In essence they are all used to apply one metal to another using heat and can be used to permanently bond two metals together, either as a joining method or as a coating. A number of welding techniques can be used to perform the hardfacing of components. Hardfacing involves applying a more wear or corrosion resistance material to a base.
‘HVOF’ is a thermal spray process which is used specifically for hardfacing of components. Powdered materials are taken, heated up and fired out at high velocities to form a coating with a strong bond.
Manual Welding is the cheapest of the processes and has an advantage in that the equipment is relatively lightweight and portable. With both Fused Overlays and HVOF, because of the higher forces involved it is more common to carry out any coating on a lathe/gimbal/with robotic arm. Both of these processes also involve specialist equipment and so are more expensive.
Both Manual Welding and Fused Overlays have higher heat impact than HVOF. This is one of the distinct advantages of HVOF in that Welding may cause thermal distortion of the part and so cannot be used on any tight tolerances or critical dimensions.
Size of Components
For larger sized surfaces, Welding is preferable to HVOF due to its lower cost and practicality. Most often HVOF will be carried out inside a specially designed booth for the best results and not by hand, making it impractical for work on large components. Where HVOF does have an advantage is that because it is a process with higher process control, it can be carried out on components with critical and tight tolerances, without causing thermal distortion which may occur with welding. HVOF is better suited to medium sized components, although at B&B we have successfully coated 2 inch diameter ball valves in the past. As general guidance however, neither of these processes are recommended for smaller and intricate parts.
Choose Welding if…
You have a large sized surface that requires a thick build-up of material and do not need to worry about any thermal distortion.
Choose HVOF if…
You have a small to medium sized component that requires a hard surface whilst maintaining critical dimensions or tight tolerances.
Get In Touch
If you have any questions, please get in touch with B&B Precision. We provide HVOF coatings from our specially designed, CO² controlled spray booth. All of our coatings are carried out by a KUKA robotic arm and we have our own on site metallurgical laboratory to test the quality of our coatings.