A beginner’s guide to thermal spraying and coating technologies

A beginner’s guide to thermal spraying and coating technologies
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When it comes to thermal spraying, there are several good options available, all of which have their own pros and cons. In terms of processes, there are two main categories: higher-energy and lower-energy types.

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Higher-energy processes

The higher energy processes include plasma, high-velocity oxyfuel (HVOF) and detonation spraying.

These techniques are intended to produce coatings that have lower porosity and levels of oxides, together with an increased adhesion to the substrates. This can be achieved thanks to the higher impact velocities of the spray particles.

These processes need significant capital investment, including sound attenuated spraying booths and mechanised guns.

Plasma spraying is a high-energy process that involves spraying molten or heat-softened material onto the surface of another (the ‘substrate’) to provide a coating. Thermal plasma spray is used across many industries despite being quite expensive and complex.

HVOF spraying involves using the pressure/heat combustion of gases or liquids mixed with oxygen to create supersonic gun-barrel speeds that allow low-porosity, high-bond-strength coatings to be applied. It is used notably within the Defence and Aerospace sector for items such as inner cylinders, landing gear, actuators, hydraulic rods, and GTEs.

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Detonation spraying uses a mixture of acetylene and oxygen to propel the powder onto the substrate at a very high rate of speed. The coatings produced are of very high quality.

You can learn more about thermal plasma spray by looking at the website of an expert today.

Lower-energy processes

The two main processes that are deemed low-energy are arc spraying and flame spraying. These processes are commonly used for protecting steel structures from corrosion.

Arc spraying is the method that gives the highest deposition rates and bond strength. It is also the most cost-efficient, mostly due to lower power requirements and lower material costs. However, this process can produce a large amount of dust and fumes and the overall quality of the coating is lower than that achieved by HVOF or Plasma.

Flame spraying is still widely used despite being one of the older techniques. It is fairly simple, low in cost, does not require mechanised manipulators, and dust and fume levels are low.

Compared to higher-energy processes, lower-energy processes require less investment and equipment. They are also often undertaken on site or in open workshops.

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