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High velocity coatings have become a critical advancement for improving component durability and operational efficiency. Among these technologies, High Velocity Air Fuel (HVAF) is a standout. 

HVAF is a specialised thermal spray process that employs a high-velocity, combustible air-fuel mixture to propel coating particles onto a surface.  

This method produces a dense, low-porosity coating with strong adhesion and finely tuned mechanical properties.  HVAF has set a high standard in surface engineering for performance and longevity. 

Why Choose HVAF?

  • Surface Property Enhancement: HVAF coatings significantly improve surface properties such as hardness, wear resistance, and corrosion protection. These enhancements are critical for applications ranging from aerospace to industrial machinery, where superior surface properties translate into longer service life and enhanced performance. 
  • Unmatched Durability: The dense, low-porosity structure of HVAF coatings provides exceptional resilience against wear and environmental degradation. This durability not only reduces maintenance needs but also extends the lifespan of components, offering robust protection against corrosion and mechanical damage. 
  • Superior Adhesion and Bond Strength: HVAF coatings are known for their exceptional adhesion, with bond strengths often exceeding 80 MPa. This high level of adhesion minimises the risk of delamination and premature failure, ensuring reliable performance even under challenging conditions. 
  • Versatile Material Selection: HVAF technology is highly versatile, compatible with a wide range of materials including ceramics, metals, and composites. This flexibility allows for the development of tailored solutions that meet specific industry requirements, providing valuable tools for applications across different sectors. 
  • Cost-Effective Performance: Despite a higher initial investment, HVAF technology offers significant long-term benefits. The durability and reliability of HVAF coatings lead to reduced maintenance and replacement costs, making it a cost-effective solution for industries seeking to optimise their operational expenses and extend the lifespan of their equipment. 
  • Low-Temperature Process: HVAF operates at lower temperatures compared to other thermal spray methods. This reduces thermal stress on components, preserving their integrity and preventing adverse microstructural changes. This is particularly important for applications requiring precision and stability. 

Applications and Materials

High velocity (HV) spraying is an effective method for applying high-quality coatings, especially those composed of cermets such as tungsten carbide cobalt (WC/Co), tungsten carbide cobalt chromium (WC/Co/Cr), and chromium carbide nickel chromium (CrC/NiCr).

These coatings, typically ranging in thickness from 0.1 to 2 mm, are characterised by their low porosity—generally less than 1% by volume—and low oxide content.

They offer robust adhesion, with bond strengths often surpassing 80 MPa, making them highly valuable in various engineering and manufacturing contexts.

HVAF coatings enhance the surface properties of components, enabling the production of cost-effective, high-performance parts from inexpensive or lightweight materials.

This makes them an attractive option for industries looking to improve the efficiency and lifespan of their equipment and components.

Commonly Deposited HVAF Coatings

When deciding on which material to use, we usually determine the performance, durability and suitability for specific applications.  

Below are some commonly deposited materials used in HVAF coatings, each being able to cater to a range of needs for industries such as Mining, Defence and Manufacturing. 

  • Tungsten Carbide (WC): Known for its excellent wear resistance, tungsten carbide coatings are ideal for applications such as pump components and valve seats. They can withstand temperatures up to 530°C, providing long-lasting protection in abrasive and high-temperature environments. 
  • Tungsten Carbide-Nickel Superalloy (WC-Ni): This material offers a balanced combination of wear resistance and corrosion protection, making it suitable for challenging environments like chemical processing and marine applications. The addition of nickel enhances the material’s resistance to corrosion, providing a durable barrier against harsh chemical exposure and saltwater. 
  • Chromium Carbide (CrC): Chromium carbide coatings are recognised for their superior resistance to solid particle erosion and high-temperature stability. They are particularly effective for protecting hydraulic cylinders and turbine shafts, which operate under extreme conditions, withstanding temperatures up to 900°C. 

What are some considerations of HVAF Coatings?

While HVAF coatings is a superior product, these are some important factors to consider: 

  • Operator-Friendly Process: HVAF spraying is relatively straightforward, once parameters are set, they don’t require frequent changes, enabling intermediate-level workers to operate the system effectively. 
  • Health and Safety: As with all thermal spraying processes, particular health and safety considerations should be addressed. HVAF spraying typically requires a specialised thermal spray booth with suitable sound attenuation and dust extraction facilities. 
  • Initial Investment: HVAF equipment may require a higher initial investment compared to other thermal spraying processes. 
  • Automation Preferred: Although manual operation of a HVAF spray gun is possible, automated manipulation of the gun is strongly recommended. 
  • Line of Sight Limitations: Deposition of coatings can be challenging on internal surfaces of small cylindrical components or other restricted access surfaces due to the limited line of sight. 

Evidently, HVAF coatings offers a superior solution for enhancing component performance, extending service life and optimising operational efficiency across a variety of industries.  

By improving surface properties and offering durable, cost-effective protection, HVAF coatings have become a leading choice in modern surface engineering. 

As experts in surface engineering, we are dedicated to delivering high-quality high velocity coating solutions that meet a range of needs. Harsh environments, saltwater to chemical exposure, we can help.   

Reach out to learn more about HVAF coatings and their powerful properties to protect and maintain your essential assets.  

Read about our HVAF services. 

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