Our primary thermal spray processes are detonation, high-velocity oxygen fuel (HVOF), plasma, flame, and arc.
• Detonation Spraying
This is a proprietary process that was invented at Praxair Surface Technologies. Gas and powder are combined in controlled detonations and blasted at supersonic speeds onto the part. Common materials are tungsten carbide or chrome carbide, metallic alloys, ceramics, and cermets.
• High-Velocity Oxygen Fuel
This process is relatively new and has propelled the thermal spray application range into places that used to be unreachable. In HVOF spraying, a gaseous fuel like hydrogen or liquid fuel like kerosene, is mixed with oxygen and combusted inside the combustion chamber of the torch at high pressure. The powder is injected into the flame and heated and accelerated due to supersonic speed of the gas’s velocity. This produces very dense coatings. The HVOF process is the most common technique for thermal spraying wear and corrosion-resistant carbides as well as Hastelloy, Tribaloy, and Inconel alloys.
• Plasma Spraying
Plasma spraying is usually considered to be the most multifaceted of the thermal spray processes. Gases like argon and hydrogen are passed through a torch throughout the plasma spraying operation. The gases are dissociated and ionized through an electric arc. The atomic components recombine past the nozzle and they give off an immense amount of heat. The plasma core temperatures are usually more than 10,000℃, which is more than the average melting temperature of any material. The powder is injected into the plasma plume where it is melted and projected toward the workpiece.
• Flame Spraying
This process is low cost and can easily be performed in the shop or onsite. It is also known as oxy/acetylene combustion spray and is the earliest thermal spray technique that was developed 100 years ago. Oxygen and fuel gas such as acetylene, propane, or propylene is fed into a torch and lit into a flame. Wire or powder can be injected into the flame where it melts and is then thermally sprayed onto the workpiece. Stainless steels, nickel, aluminides, Hastelloy alloys, tin, and babbitt metal (a tin-based alloy) are a few of the materials that flame spraying can apply.
• Arc Spraying
During this process, two wires are brought into contact with each other at the nozzle at the same time. When the electrical load is placed on the wires, it causes the tips of the wires to melt once they touch. Atomizing gases like air or nitrogen are used to clear out the molten material off the wires to move it to the workpiece. Arc spraying is relatively cost-effective and readily functional in the field. Velocities that have low particles allow for high-maximum coating thickness for any specified material. Materials that are typically applied by arc spraying include stainless steels, Hastelloys, nickel aluminides, zinc, aluminum, and bronze.
