HVOF (High-Velocity Oxygen Fuel) is a surface treatment process belonging to the thermal projection category that can also be applied locally within a confined area. It uses a combination of high-speed fuel (such as natural gas or kerosene) and oxygen to melt and accelerate particles of metallic or ceramic dust to the surface of a part or component. The result is a dense, adherent, and highly resistant coating capable of resisting abrasion, erosion and impact wear, even at temperatures above 850°C which improves the mechanical properties and service life of the treated surface.

Processes Details

The HVOF process involves the following steps:

  1. Surface preparation: The part to be treated should be thoroughly cleaned to remove any dirt, rust or contaminants that may affect the adhesion of the coating.
  2. Preparation of the powders: Powdered materials, which can be metals such as stainless steel, nickel alloys, tungsten carbides or ceramics such as aluminium oxide, are selected according to the desired properties of the coating.
  3. Flame generation: It mixes fuel with oxygen and burns in a device called a burner, creating a high-speed flame.
  4. Projection of the powders: The powders feed to the flow of the flame, where they are melted and accelerated at high speed.
  5. Surface impact: Molten powder particles impact the surface of the substrate with a high kinetic energy, allowing a strong metallurgical bond between the coating and the base material.
  6. Cooling and solidification: High impact speed and subsequent heat dissipation allow particles to cool quickly and solidify into a dense, uniform layer.

Among the most common coatings used in the HVOF process are tungsten carbide + cobalt + chromium and chromium carbide + nickel + chromium. These coatings offer excellent resistance to extreme wear and temperature conditions.
After the HVOF coating application, a grinding operation of the coating to obtain the desired geometry and surface quality is often conducted afterwards.

Parts and Components

HVOF is widely used in a variety of parts and components to improve its performance and durability. Some of the common applications include industrial components such as rollers, shafts, cylinders, and rods; aerospace components such as turbines, compressors, and engine internal components; automotive parts such as valves, pistons, cylinders, and drive shafts; cutting tools such as drills, blades, cutters, and shaping tools; and processing and pumping equipment such as impellers, rotors and pump shafts.

In the specific case of landing gear parts, a sequential process is followed that includes the first step of Shot Peening to improve fatigue resistance, followed by hard chrome plating or HVOF coating. Finally, the parts are subjected to a grinding operation on their coating, according to the type of coating used.

TTT Group holds the corresponding aeronautical certifications, which guarantees the application of these processes with the highest quality standards in aeronautical applications and in other sectors of the industry.

Fields of Application

HVOF is widely used in various industrial sectors due to its surface improvement benefits. It is commonly applied in aerospace and defence industry to improve the efficiency and corrosion resistance of engine components and aerospace systems, in the oil and gas industry to protect components exposed to corrosive and abrasive environments, in the manufacturing and machinery industry to increase service life and reduce wear on critical parts, in the automotive industry to improve the strength and efficiency of engine and transmission parts, and in the processing and chemical industry to protect pumping equipment and valves used in chemically aggressive environments.

HVOF en Bombas