In this blog, we are presenting you a guide to different metal spraying processes. As you may (or may not) know, metal spraying is highly customisable. Results can be achieved with various materials, applications, and finishes. Learn more on how we deliver high-quality, compatible metal spray coatings.
What Is Metal Spraying?
Metal spraying is an engineering coating technology designed to improve the surface properties and durability of components. It is used across a range of industries wherein parts, surfaces or components must endure harsh environments while maintaining their integrity.
To extend the lifespan of materials, the most common applications of metal spraying are in architecture, machine engineering, aerospace, and motor vehicles. From extreme temperatures, moisture, corrosion, abrasion, friction and gradual wear, all these applications require added protection.
In a lot of cases, it is viewed as impractical to use the spraying material for the component instead. This is due to weight, availability, and cost. It is however possible to achieve similar robustness by commissioning metal spraying.
Metal spraying is a highly customisable technology. From finishing coatings- decorative and corrosion protection- to surface coatings- wear control or thermal barrier. Not only can a wide range of materials be used, metallic or non-metallic, but there are alternative methods used to achieve optimal results.
Types Of Metal Spraying Processes
Flame Spraying
Flame spraying is one of the oldest, tried and tested methods of metal spraying.
The process is initiated by a chemical reaction between a fuel of combustion and oxygen. This is formed into a wire and transferred to the nozzle of a heat gun/machine. When compressed air is then applied, it forces the particles out of the nozzle and onto the substrate.
When using a powder flame spray, the flame will soften the powder particles, which are then coated in the flame gases and projected through the nozzle.
Flame Spraying Application
Flame spraying is commonly used for:
- Corrosion protection
- Reclamation of worn components, such as shafts
- Enhancing surface technology and component performance
Advantages To Flame Metal Spraying Processes
- Cost-effective solution in comparison with other metal spraying processes
- Reduced dust and fume levels associated with arc spraying can be completed without the need for a spray booth
- The price of equipment is generally lower while deposition rates remain high
Disadvantages To Flame Metal Spraying Processes
- Difficulty in application to specific, hard-to-reach areas
- Potentially a lower quality finish so is better suited to less demanding environments
Arc Spraying
By using the heat of an electric, wires are melted down. The molten particles are then atomised with compressed air, which is the process of separating the liquid into small, sprayable droplets. This forms a spray steam, which is accelerated onto a prepared substrate.
Arc Spraying Application
Arc spraying is commonly used for:
- Corrosion protection in marine and industrial settings
- Worn surface restoration
- Wear resistance against erosion, abrasion, and/or friction
- Thermal insulation against extreme temperatures and thermal cycling
Advantages To Arc Metal Spraying Processes
- Low cost of equipment and materials and significantly lower operating costs for large-scale applications i.e. buildings and structures
- High deposition rate, meaning the coating coverage is buildable
- High-quality adhesion and bond strength ensuring long-withstanding protection and performance
- Minimal heat input when compared to plasma spraying, which reduces the risk of thermal distortion
Disadvantages To Arc Metal Spraying Processes
- Higher levels of porosity, which could alter its effectiveness if not properly sealed
- Noise and fumes produced in the application may require protective measures to be taken
Plasma Spraying
In terms of engineering, plasma refers to the process of heating gas to a high enough temperature to where it ionises and can conduct electricity.
The process behind plasma spraying involves connecting an electrically charged arc between the nozzle and the electrode in the plasma gun. When projected, the plasma jet and powder particles are accelerated through the nozzle and form a strongly adherent coating.
Plasma Spraying Applications
Plasma spraying is commonly used for:
- Thermal barrier coatings for aerospace applications, such as turbines
- Wear and corrosion protection
- Repair and restoration of worn surfaces
- Used to enhance the biocompatibility and durability of prosthetics and implants
- Used for conductive coatings in electrical applications
Advantages To Plasma Metal Spraying Processes
- Highly controlled finish in terms of thickness, composition, and microstructure of the final coating
- High levels of kinetic energy result in strong adhesion
- Immense durability and can withstand extreme temperatures and hard conditions
- Able to achieve precision on smaller, complex parts
Disadvantages To Arc Metal Spraying Processes
- Finishings of arc spraying tend to be rough, so may require further finishing steps, like grinding or polishing
- Not suitable for all materials, especially those that are sensitive to oxidisation or have extremely high melting points
HVOF Spraying
High Velocity Oxygen Fuel (HVOF) involves the process of mixing fuel and oxygen and then igniting the formed mixture in a combustion chamber. In a nozzle, powder is introduced, to form a stream that is projected onto applications.
HVOF Applications
HVOF is commonly used for:
- Used on industrial machinery and aerospace components to prevent wear
- Corrosion protection in the oil & gas industry
- Surface hardening of agricultural equipment
Advantages To HVOF Metal Spraying Processes
- Low porosity and highly dense coatings provide better protection against moisture
- High-performance durability, ideal for mechanical parts
- Resistance to oxidisation
- A smooth coating finish, therefore does not require additional steps
Disadvantages To HVOF Metal Spraying Processes
- Complex application process and set-up requiring skilled operators and expertise
- Limitations to applicable coating materials due to levels of oxidisation
- Stringent standards for substrate preparation for optimal results
Metal Spraying Processes With Alphatek
At Alphatek, we adopt a host of metal spraying processes, such as flame spraying, arc spraying, plasma spraying, HVOF, Teflon, and PTFE.
Our metal spray coatings are across a vast range of industries and can offer solutions to various conditional challenges. With over 100 years of experience in coating science, we have the knowledge and expertise to offer a compatible solution to your engineering woes.
If you would like to know more about the science behind metal spraying or our services, then please feel free to contact us. We’re happy to help!
