When it comes to arc spray and HVOF there are some major differences such as cost and durability that can affect whether one system is better than another for your application. In this blog, we will look at the differences and advantages of arc spray and HVOF so you can decide which works best for your application. If you still have questions at the end we'll leave a contact form so you can get in touch too.
What is Arc Spray?
Before we jump into the benefits of arc spray and how it’s different from HVOF, we need to make sure we all understand what arc spray is.
Arc spray (which is sometimes referred to as twin wire arc spray) is a process that uses an electric arc to melt wires. In the arc spray process, the raw material in the form of a pair of metallic or cored wires is melted by an electric arc. This molten material is atomised by a cone of compressed air and propelled towards the work piece. The molten spray then solidifies on the component surface to form a dense, strongly adherent coating. Arc sprayed deposits have a higher degree of bond strength than some other thermally sprayed deposits and the use of compressed air and electricity alone mean more economic coatings.
Benefits of Arc Spray
Arc spray is a very good, cost effective method to apply metallic coatings in a very wide range of applications and is one of the most versatile of all of the thermal spray processes. It is a simple process to provide corrosion protection coatings to steel fabrication or is as easily capable to provide engineering coatings to re-build or change the surface properties of the sprayed objects.
The process can enable the highest production rates of all of the spray processes, capable to spray in excess of 150kg/hour of zinc for example.
Corrosion protection applications include range from small brackets, gates/fences and playground equipment right up to entire ships, offshore oil platforms and wind turbines. The range of engineering coatings is almost endless from hydraulic pistons, clutch plates, bearing and seal areas, air conditioning components, boilers and vessels and rolls for the paper and print industry. This is a very small list of possible applications.
Other benefits of arc spraying are as follows:
- Low power consumption compared to plasma or HVOF.
- Simple push-button operation.
- Low heating of the substrate used makes arc spray useful when it comes to thermally sensitive substrates. For example, capacitors and electronic components.
- A range of porosity levels can be achieved to enable the coating properties to match the application requirements.
- Arc spray doesn’t require the use of combustion gases or produce a high-energy plasma; meaning that it poses fewer health and safety risks than other thermal spray processes.
- Arc spray process offers lower cost and high throughput coatings in comparison to the HVOF spraying process.
What is HVOF?
Just like before, we need to make sure that everyone understands what HVOF is and the process behind it before jumping into the benefits of using it. So, what is HVOF?
High-velocity oxygen fuel (HVOF) is a process to apply very dense, strongly adhered coatings. The way the HVOF process works is by liquid fuel and oxygen being fed into a combustion chamber where they are ignited, producing a hot high-pressure gas stream. This is then accelerated through a de-laval (converging/diverging) nozzle increasing the gas velocity to around 1500m/sec and the pressure to slightly below atmospheric. At this stage, the powder can easily be injected into the gas stream.
The gas stream heats and accelerates the powder particles to around twice the speed of sound, simultaneously softening them. They impact onto the sprayed surface with tremendous energy to form a very dense, strongly adhered coating. The Metallisation HVOF system does not melt powders but only softens them. This is because less heat is imparted to the particles and the dwell times are very short, oxidation and decomposition are minimal in HVOF coating.
HVOF coatings are more costly and slower to apply than arc spray coatings but the benefits of the improved coating characteristics can make it an excellent choice.
Benefits of HVOF
Just like arc spray, there are many different advantages and benefits to using HVOF. For example; HVOF coatings can apply materials that include Tungsten Carbide which makes coatings with exceptional wear protection – up to 10 times greater than hard-chrome plating for example. The process lends itself to high value applications, significantly extending the life of components such as mud rotors, gate and ball valves in the oil/gas sector or hard chrome replacement of aircraft landing gear or hydraulic pistons. Some of the benefits of HVOF coatings include…
- Retention of powder chemistry due to the reduced time at temperature.
- There is lower oxide content due to there being less in-flight exposure time.
- There is higher density (lower porosity) due to there being greater particle impact velocities.
- Improved corrosion protection due to there being less through-thickness porosity.
The Final Finish
There is a large range of benefits and advantages of using arc spray and HVOF. But which one is best for you? To find the answer, speak to a member of our team today and we will help to find the ideal solution that fits your budget and the environment that you work in.
Metallisation has been working in the metal coating industry since 1922, in that time becoming the leading UK developer, manufacturer and worldwide supplier if a full range of metal spraying equipment and consumables. So, if you have any questions or would like to find out more about arc spray or HVOF; get in touch with a member of the Metallisation team today on 01384 252 464 or send us an email on firstname.lastname@example.org. We look forward to hearing from you.