Explore the science behind thermal spray coatings in this blog from Alphatek!
Thermal spray coatings are used in a huge variety of applications today and are key to cost reductions, extending the life of parts, improving performance, and even helping keep people safe.
Understanding the science behind thermal spray coatings is obviously key here at Alphatek, as trusted thermal spray coating specialists, and also because we are continually developing and innovating our own new thermal spray solutions for clients. But do you know the science behind this fascinating technique? Which is older than you may think?
Read on for the science of thermal spray coating technologies.
What Are Thermal Spray Coatings?
At its most simple, thermal spray coating is the process of heating or melting one substance (usually metallic or ceramic) and spraying it onto another surface.
This process is used to enhance or renew surfaces, giving the receiving surface properties it wouldn’t have without the coating.
Thermal spray coatings are used in a wide variety of industries and can be used on anything from cars to moulds in a glass factory. They are used frequently in the oil and gas, automotive, aerospace, and rail industries.
The additional properties thermal spray coatings provide range from wear control to protection from extreme weather conditions.
The Basics Of Thermal Spray
During thermal spraying a material known as a feedstock must be heated or melted in order to spray it onto another surface – the feedstock can be heated in several different ways, depending on the technique being used and the required finish. Some techniques use electrical means to heat feedstock such as plasma or arc spraying, and some methods use a combustion flame with varying types of gas.
There are different processes that reflect advancements in technology and the varying nature of the items that need spraying, plus the properties the client requires from their thermal spray coating.
Items for spraying are usually metallic but a variety of other materials can also be thermal spray coated.
Materials that can be used for coating can include alloys, ceramics, and composites. The form the feedstock can take can also vary but is usually wire form or a powder. Once the feedstock is in a molten or semi-molten state, it is accelerated towards the item being sprayed (referred to as a substrate).
These particles stick to the surface, resulting in the finished coating.
The Science Of Coating Deposition
When spray particles are deposited onto a substrate, they form what are known as splats – the particles flatten to form lamellae-like structures that quickly harden. This forms the coating which can be built at different thicknesses depending on client needs.
In order for the splats to adhere to the substrate, referred to as ‘splat hold’, the surface of the substrate must be properly prepared for thermal spray coating. This is key to achieving a good quality finish.
But what is the process that makes the coating ‘stick’ to the substrate, and stay there?
The metallurgic bonding that occurs after a coating is sprayed results from the base substrate (the surface being sprayed) wrapping around the particles because of the high speed at which the coating is accelerated towards the substrate.
As mentioned, for this process to work, the substrate must be thoroughly prepared, this is usually done through grit blasting.
Thermal Spray Techniques
There are several different thermal spray processes that are used in order to achieve different results and depending on what the coating is, and the surface being sprayed.
These include:
- Plasma spraying
- Flame spraying
- Wire arc spraying
- High velocity oxy fuel spraying (HVOF)
- High velocity air fuel spraying (HVAF)
- Spray and fuse
- Cold spraying
Again, different processes are needed depending on customer needs, the bond strength of the coating, the substrate, and the properties the customer wants to achieve.
Thermal Spray Coating Materials & Applications
Initially, thermal spray coatings were restricted to metals, but innovations mean ceramics and composites can also now be used. Even plastic can be used too.
techniques are preferred in different industries depends on a variety of factors which include:
Because of different techniques such as cold spraying, even the surface being sprayed doesn’t need to be metallic. This method is also useful for flammable materials because of the lower temperatures used in this technique.
Why some
- Cost efficiency
- Coating properties required
- Substate being sprayed
- The versatility of the coating
Another factor is can the surface being sprayed be brought into a workshop to be sprayed – electric arc spraying, for example, can be portable because it only uses compressed air.
Alphatek
We hope you enjoyed this brief explanation of how thermal spray coatings work and learned a little bit more about the processes we use in the industry.
We are thermal spray coating specialists based in Lancashire and work with a variety of industries, worldwide, including some recognisable automotive brands.
Our customers come to us because we can be relied on for our problem-solving skills when it comes to finding new or unique ways to apply thermal spray coatings.
If you would like to chat about your requirements or speak to us about developing a coating to meet your expectations, please contact us or give us a call. We look forward to hearing from you.
