Metal Spraying
Metal spraying is a surface coating process of applying materials to a component to increase properties such as corrosion, wear, or heat resistance, as well as for conductivity and salvage purposes.
Metal spray processes have been effectively used for many decades across a range of industries. Often referred to as flame spraying, as it is a flame that produces the heat required to melt the material, metal spraying techniques are used in industries including automotive, oil & gas, food production and packaging. The metal spray process involves heating the material, either wire or powder, until molten, before compressed gas blasts it onto the component. The result is a continuous layer that is well adhered to the component, with a high-quality finish and a quick turnaround due to the high deposition rate of the process.
There is a wide range of materials that can be applied using metal spraying techniques. Materials are carefully selected for each application to ensure the desired properties are achieved and components are able to perform as intended in their final operating environments.
For guidance, the Poeton metal spray team can assist with all aspects of the metal sprayin
THERMAL SPRAY
Apticote 800
Metal spraying uses similar materials to Plasma spray but is applied differently. Typical applications are:
- Electrical conductivity
- Decorative finish
- Thermal barrier coatings
- Corrosion protection
- Heat exchangers
- Heat shields
- Wear resistance
Corrosion protection
One of the key benefits of using metal spray is the increase in corrosion resistance. Metal sprays containing material such as aluminium and zinc can be easily applied in a uniform thickness and extend the life of components in aggressive environments.
Poeton have successfully used zinc spray coatings (Apticote 800/129) to increase the corrosion resistance in a variety of industries. Examples include aluminium & steel window frames, automotive exhaust systems, and offshore equipment.
Wear resistance
Metal spray coatings can improve wear resistance and lengthen the lifespan of components. The wide range of materials available allows for components to be protected from different types of wear.
For example, coatings containing molybdenum will protect against sliding wear and coatings with tungsten carbide will provide protection in harsher environments such as oil pumping valves and automotive break discs.
Thermal barrier coatings
Ceramic based metal spray coatings produce excellent thermal barriers and protect components from heat sources such as engines, combustion chambers and gas turbines. Thermal barrier coatings also enable the use of high-performance materials such as carbon fibre in applications where they normally can’t operate.
For example, aerospace and automotive manufacturers can benefit from carbon fibre’s strength, durability, and weight before utilising Apticote 800/32 to increase its temperature resistance up to 1600°C.
Ytrria stabilised zirconia is often the material of choice for this application.
Abradables
Abradable metal sprays are designed to intentionally wear away when they come into contact with a mating part in a way that causes no damage to the substrate. By doing so, it creates the optimum clearances between the two components and ensures maximum performance is achieved.
Abradable metal spraying is commonly used in gas turbine engines, impellors and shafts where a seal is required as it is often difficult to manufacture parts with such a small tolerance. We regularly coat rings for gas turbines with an abradable so that as the turbine is operated the coating is naturally eroded away until there is an exact seal between the parts. This dramatically improves the efficiency of the turbine.
Non-slip
Uncoated surfaces, especially metal surfaces, can often become slippery when water or oils are applied to them. Aluminium based metal sprays, applied with deliberate surface roughness are very effective at reducing both slipping and corrosion.
Non-slip metal spray coatings have been utilised by a large military helicopter manufacturer to provide a surface with consistent grip in a variety of conditions. Apticote 800/127, an aluminium based metal spray, passed repeated tests in all conditions and is accredited to BS 7976-2.
Salvage & restoration
Damaged, worn or eroded parts can be repaired with the use of metal sprays. The affected area is cleaned and blasted, before a material similar to the component is applied and built up. The metal spray coats to an oversize to allow for machining back to the correct shape and dimensions.
Marine turbochargers and aerospace rotor hubs have benefitted from Apticote 800/61 to restore components. This bronze metal spray extended the service life of the components as part of a full restoration project, saving on the cost of purchasing brand new parts.
Self lubricating
Metal sprays can provide hard and lubricious surfaces that offer excellent dry-running properties. They are ideal in applications that require resistance to fretting and sliding wear due to the low coefficient of friction. Self-lubricating metal sprays provide an ideal solution when it is too complex to embed wet lubricants, or the equipment is hard to gain access to.
Apticote 800/125, a molybdenum-based metal spray, provides the self-lubricating properties required for rotary engine housings for a manufacturer of UAVs, removing the need for monitoring and maintaining wet lubricants. This metal spray is also popular in automotive and transport equipment such as bearings and gears as well as difficult to access off-shore wind and subsea equipment.
Non-stick
Metal sprays can be combined with polymers to create advanced non-stick coatings. The unique properties of both materials create a surface that is both tough, hard and has a low coefficient of friction to prevent sticking. These coatings also help to reduce wear and corrosion.
Non-stick metal spray coatings have been applied by Poeton for packaging companies such as Tetra-Pak. A new coating was developed to prevent machinery that was responsible for sealing cartons from failing over time. An investigation discovered that the sealing pads themselves were separating from the machinery and an FDA compliant Apticote coating was used to secure the sealing pads to the substrate. This resulted in a significant decrease in downtime on Tetra-Pak’s production line.
More Thermal & Metal Sprays
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