What is Spray Welding?
Spray welding refers to a variety of welding processes that use thermal spraying. It is an industrial process in which a powder or wire is atomized with compressed gas at high speeds and sprayed onto a metal surface.
Spray welding employs industrial plasma, flame, detonators, arc spray, and high-velocity oxyfuel. Because of the significant heat generated by spattering welding, procedures and regulations must be strictly followed to avoid harm to people and the environment.
What is the Process of Spray Welding?
Thermal spray is a broad term that refers to a variety of coating processes. The entire welding process involves the use of coating material, such as a rod, powder, or wire, which is melted by various energy sources.
It is an industrial coating process that consists of a heat source and a coating material melted into droplets that are sprayed at high velocity. An atomization jet or gas propels the spraying toward a substrate.
Thermal spraying is a versatile process that is also known to be highly efficient. It can be an excellent alternative for a variety of surface treatments, including heat or nitride treatment processes, chrome, nickel plating, and anodizing, among others.
Individual preferences influence the thickness of the coating. The coating restores worn-out parts and basic machine components. It can also be used to improve the element’s performance and durability. If properly cared for, this can last up to 70% longer.
Different Types of Spray Welding Techniques
- Arc Spray Welding
Spray arc welding is one method of transferring molten material in the form of many small droplets, each with a diameter smaller than the filler wire. The arc is stable and spatter-free because there are no short circuits.
The current and voltage values must be above certain limits for spray arc welding to be successful. As a result, the workpiece receives more heat than with short-arc welding, and only materials with a thickness of 5 mm or greater are suitable for spray-arc welding.
Because of the high heat input, the weld pool is also large, so welding must be done horizontally. It should be noted that using CO2 as the shielding gas does not result in a pure spray arc.
The shielding gas must be pure argon, preferably with a trace of CO2 (no more than 25%) or O2. Spray arc welding is especially well suited for MIG welding of aluminum and stainless steel, where the primary shielding gas is argon.
- Flame spraying Process
Flame spraying, also known as oxy/acetylene combustion spraying, was the first thermal spraying technique developed around 100 years ago. It operates on the same principles as a welding torch, but with the addition of a high-velocity airflow to propel molten particles onto the substrate.
The coating material can be wire or powder. Flame spray coatings are frequently melted after application to improve adhesion and coating density.
- High-Velocity Oxyfuel (HVOF)
The HVOF (High-Velocity Oxy-Fuel) process burns oxygen and a limited number of flammable gases such as propane, propylene, or hydrogen. Although the HVOF system employs the basic combustion principle, the spray gun is not the same as a standard oxy-fuel spray gun.
Higher flame temperatures and velocities are produced by the HVOF gun differences. As a result, the powder is more thoroughly melted, and there is more kinetic energy available to “flatten” the melted coating particles. Superior bond strength and coating density are produced by the HVOF process.
- Plasma spray process
The plasma spray process (non-transferred arc) uses inert gases fed past an electrode to induce the “plasma” state of the gases. A tremendous amount of heat is released when the gases exit the nozzle of the gun apparatus and return to their normal state.
In the plasma “flame,” a powdered coating material is injected and propelled onto the substrate.
- Spraying with Detonation
Detonation spraying is one of many thermal spraying techniques used to apply a protective coating to the material at supersonic velocities to change its surface characteristics. This is done primarily to increase a component’s durability.
- Cold Spray Process
Cold spraying (CS) is a method of coating deposition. Solid powders (1 to 50 micrometers in diameter) are accelerated to 1200 m/s in a supersonic gas jet. Particles deform and adhere to the surface as a result of the impact on the substrate.
The spraying nozzle is scanned along the substrate to achieve uniform thickness. Cold spraying can deposit metals, polymers, ceramics, composite materials, and nanocrystalline powders.
Advantages of Spray Welding
- Spray welding ensures a smooth weld
- It has high penetration and is suitable for metal thicker than 3/16
- It has high weld deposit rates, which increases productivity
- The presence of very little spatter
- Inexpensive: use of less expensive material and strengthen by spray
- Spray welding is versatile, most metals, ceramics, and plastics can be sprayed
- Works in a variety of thicknesses
- Fast processing speed: spray times from 3 to 60 lb/hour (depending on the process used)