What is HVOF Coating – HVOF Thermal Spray Process, Materials, Benefits, Machine, Applications


With the continuous development of modern manufacturing technology, the demand for the lifespan and performance of mechanical components is increasing. In this context, High-Velocity Oxygen Fuel (HVOF) coating technology, as an advanced thermal spray method, successfully meets various performance requirements such as wear resistance, corrosion resistance, thermal conduction, insulation, and conductivity through flexible and adjustable flame velocity and temperature. HVOF coating, with its unique characteristics such as high flame velocity, low temperature, and high coating bond strength, provides an efficient and reliable surface protection and enhancement solution for various industries. If you are not familiar with HVOF, join us to delve into the preparation process, coating characteristics, and its extensive applications in metallurgy, paper printing, petroleum industry, hydraulic pneumatic equipment, power systems, wire drawing equipment, and more.

What is HVOF Coating?

High-Velocity Oxygen Fuel (HVOF) coating is an advanced thermal spray method that deposits molten or heated materials onto a surface, forming a uniform coating. Raw materials are heated through methods such as HVOF thermal spraying or combustion flames, enabling the formation of the coating. Thermal spraying can provide relatively thick coatings (ranging from 20 micrometers to several millimeters, depending on the process and materials) with a high deposition rate compared to other plating processes, making it suitable for large-area coatings. Coating materials for thermal spraying include metals, alloys, ceramics, plastics, and composite materials, supplied in the form of powder or wire. These materials, when heated to a molten or semi-solid state, are accelerated onto the substrate in the form of micrometer-sized particles. The energy source is typically combustion or electric arc discharge. The resulting coating is formed by the accumulation of a large number of ejected particles, and the surface may not significantly increase in temperature, allowing the coating of flammable materials. Coating quality is usually evaluated through parameters such as porosity, oxide content, hardness, bond strength, and surface roughness. Generally, coating quality increases with an increase in particle velocity.

What Does HVOF Stand For?

Key features of HVOF coating include extremely fast flame velocity, exceeding the speed of sound, reaching 2200 m/s, which is 5-10 times faster than typical thermal spray processes. Due to its high speed, powder particles have significant kinetic energy, forming a high-density coating with good bond strength on the substrate surface. The oxygen content in the flame of HVOF coating is lower, the temperature is moderate, and the flame velocity is extremely high, effectively preventing oxidation and decomposition of powder coating materials. Therefore, it is particularly suitable for spraying carbide coatings with excellent wear resistance. Due to fewer impurities in the spray, residual stresses designed in some cases can be achieved, allowing for thicker coatings and high spraying efficiency.

Research and evaluation of HVOF flame spray technology in the preparation of nano-tubes, oxide content, macro and micro hardness, bond strength, and surface roughness indicate that coating quality generally improves with an increase in particle velocity. This spraying method finds extensive applications in the field of wear-resistant coatings, providing high-performance surface protection and enhancement for various industrial sectors.

Advantages (Features):

High-Velocity Oxygen Fuel (HVOF) is a thermal spray technology with numerous advantages. According to search results, here are the advantages of HVOF coating:


Despite the many advantages of HVOF spraying equipment, there are some disadvantages:

HVOF Coating Process & Full Form

HVOF thermal spraying is an efficient and fast coating process that can form a dense and uniform coating on the material surface in a short time. The following provides a detailed introduction to the HVOF coating process and its applications.

Step 1 – Preparation work

Before HVOF spraying, the surface of the material to be coated needs to be pretreated first. This aims to remove impurities and enhance adhesion between the coating and substrate. Commonly used surface treatment methods include grit blasting, bead blasting and chemical treatment. In addition, preparation of HVOF machine, nozzle, spray gun and other equipment is needed.

Step 2 – Coating material preparation

The coating materials used for HVOF thermal spraying are usually powders mixed with a solvent. During the preparation of coating materials, the powders need to be ground, mixed, etc. to ensure uniform particle size and thorough blending with the solvent. Additives such as thickeners and leveling agents can also be added according to coating requirements and material properties.

Step 3 – HVOF spraying

Adjust spraying parameters: Adjust the parameters of the HVOF machine such as spraying pressure, spraying distance and spraying speed according to the coating material properties and coating requirements to ensure uniform and stable spraying of coating materials onto the substrate surface.

Control spraying process: Pour the prepared coating materials into the spray gun of the HVOF machine and eject the coating materials at high speed onto the substrate surface through the nozzle. Stable spraying distance and speed should be maintained during the whole spraying process to ensure uniform and continuous spraying of coating materials on the substrate.

Coating formation: The sprayed coating materials instantly evaporate and cool upon contact with the substrate, forming a dense and uniform coating. Due to the high spraying velocity of HVOF thermal spraying, the coating particles have sufficient kinetic energy to effectively improve the density and adhesion of the coating.

Step 4 – Post treatment of coating

After HVOF spraying is completed, post-treatment work is needed to further improve the performance of the coating. Common post-treatment methods include sintering, heat treatment and CNC machining to make the coating more dense and robust, improving its wear resistance, corrosion resistance and other properties.

Step 5 – Testing and Evaluation

Quality Control: Implement testing and evaluation processes to ensure the quality of the HVOF coating. Common testing methods include hardness testing, adhesion testing, porosity testing, and thickness measurement.

Quality Assurance: HVOF coating quality assurance involves confirming that the coating meets the specified requirements and standards for the intended application. This step is crucial for ensuring the reliability and performance of the coated component or surface.

HVOF Coating Equipment (Components & Machine Price)

HVOF spraying typically requires specialized spraying equipment. This equipment includes HVOF flame spray guns or plasma spray equipment to generate high-speed gas streams.

Key Components of HVOF Spraying Equipment:

HVOF Coating Machine Price:

The price of High Velocity Oxygen Fuel (HVOF) coating machines can vary widely based on several factors such as the machine’s capabilities, size, manufacturer, and the specific technology it uses. As of my last update in September 2021, prices could range from tens of thousands to several hundred thousand US dollars. For a general idea:

However, prices can change over time due to advancements in technology, changes in market demand, and the economic environment. For accurate and up-to-date pricing, you would need to contact suppliers or manufacturers directly for quotations. Keep in mind that the cost of the machine is only part of the total investment; you will also need to consider installation costs, training, maintenance, and the cost of consumables and spare parts.

HVOF Coating Materials

HVOF thermal spraying can be used for coating various materials, including metals, ceramics, polymers, composite materials, etc. Coating materials are usually supplied in powder, particle or wire form. HVOF (High Velocity Oxygen Fuel) technology can use various spraying materials to create wear-resistant, corrosion-resistant or high-temperature coatings depending on the required coating performance and application environment of the components. The selection of these materials depends on factors such as the desired coating properties, temperatures, pressures, chemical exposures and physical abrasion that the component will be subjected to.

In addition to the material properties, the powder particle size, flowability and purity will also affect the spraying process and coating quality. Therefore, in practical applications, the material and coating design are usually selected according to specific requirements. Some commonly used HVOF spraying materials include:

Metal Alloys

Ceramic Materials

Composite Materials

Functionally Graded Materials (FGM)

Other Special Materials

Choosing the right spray material is critical to ensuring the performance of your coating. Engineers must consider factors such as the working environment, temperature, pressure, chemical exposure and physical wear that the workpiece will be subjected to. In addition, the particle size, flowability and purity of the powder will also affect the spraying process and the quality of the coating. Therefore, in practical applications, material selection and coating design are usually based on specific needs.

HVOF Coating Applications

HVOF thermal spray coating technology has found widespread applications in various fields, including aerospace, aviation engines, energy industry, automotive manufacturing, electronics, medical devices, and protective coatings. This technology provides crucial surface engineering solutions by preparing coatings with properties such as wear resistance, high-temperature resistance, corrosion resistance, and insulation.

Here’s a table summarizing the application of HVOF Coating in various industries:

IndustryComponentCoating MaterialBenefits
MetallurgicalBottom rolls of continuous annealing furnacesNiCr-Cr3C2High-temp oxidation resistance, thermal shock resistance, wear resistance
 Conveyor rollersCo-based WCExcellent wear resistance and mechanical properties
Paper and PrintingCalender rollsWCSuperior wear resistance, fatigue strength
 Coating rollsCeramicImproved hydrophilicity, prevents glue adhesion, longer lifespan than fluoroplastic coatings
PetroleumPump piston rodsWCSignificantly improved wear resistance and lifespan
 Valve seats and shaft componentsCo-based WCExcellent adhesion, adaptability under harsh conditions
Hydraulic and PneumaticPump shafts, piston rods, valve coresVariousHigh precision, low surface roughness, extended lifespan
 Spools of ball valvesMetal ceramicEnhanced sealing performance and lifespan
Power SystemsFans, impellers, boilers, steam turbine partsVariousImproved wear and corrosion resistance, safety, and economic benefits
Wire Drawing EquipmentTower pulleysWCExtended lifespan through surface reinforcement
Environmental PerspectiveGeneral applicationVariousReduction in use of hazardous materials like hexavalent chromium, aligns with environmental regulations
Economic PerspectiveGeneral applicationVariousLong-term cost savings through reduced maintenance, downtime, and replacement compared to other coatings

As technology advances, HVOF coating equipment has seen improvements in performance and efficiency, allowing them to better serve the demands of high-performance coatings. When selecting and using HVOF coating equipment, it is essential to choose the appropriate equipment model and configuration, and optimize the thermal spray coating process parameters based on the specific application requirements to ensure the coating’s performance meets the expected results.