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 materials. Materials that are typically applied by arc spraying include stainless steels, Hastelloys , Nickel aluminides, zinc, aluminium and bronze’s.
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, Zinc, Aluminum, Iron and Nickel based alloys are a few of the materials that flame spraying can apply.
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 corrosion-resistant Tungsten and Chromium carbides as well as Hastelloy, Tribaloy and Inconel alloys.
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 spaying 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˚C, 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 towards the workpiece. Common materials include carbide and ceramics.
Cold Spray, simply put, is a coating deposition method. Using a high-kinetic and solid-state coating process, Cold Spray applies either metallic or ceramic particles onto a metallic or non-metallic substrate. Metals such as Titanium, Copper, Stainless Steels and Aluminium can be applied to a substrate using Cold Spray. These particles are accelerated through a high-speed gas jet towards the desired substrate. The particles plastically deform and consolidate upon impact.
This process can be used to improve properties such as; thermal and electrical conductivity, to rebuild worn parts and to provide corrosion and abrasion protection/resistance.
Some of the benefits of Cold Spray include:
-No oxidisation of materials.
-No heat applied to the substrate.
-No limit on deposition thickness.
-No toxic fumes.
Laser Cladding is a process in which a high-powered laser is used to melt and fuse a metal powder or wire onto a substrate to create a new surface layer with improved properties. The process is used to repair worn or damaged parts or to add features to existing parts. The Laser heat source allows for very precise control over the material deposition process, resulting in minimal distortion or thermal damage to the substrate. Laser Cladding is commonly used in manufacturing and repair applications in the aerospace, automotive and medical industries.
HIGH VELOCITY AIR FUEL
High-Velocity Air Fuel ( HVAF) is a Thermal Spray coating process that involves the combustion of a fuel gas and air to generate a high-velocity jet of gases that propel coating particles onto a substrate. The process is known for its ability to produce a high-quality coating with low porosity, high bond strength and excellent adhesion. Compared to other thermal spray techniques, HVAF I is known for its relatively low heat input, which in return minimizes the risk of thermal damage to the substrate or coating material. HVAF can be used in the following applications: Aerospace dimensioning, chemical tank protection, pulp and paper industries, oil refining and drilling and auto engine part repair.
Plasma Transferred Arc
Plasma Transferred Arc (PTA) is a specialized welding process used to apply hard-facing or protective coatings to protect against wear and corrosion. The process involves creating an electric arc between a non-consumable tungsten electrode and the workpiece. The arc generates a high temperature, which ionizes a gas (typically Argon) to form a plasma. The high-energy plasma transferred arc melts the surface of the base material. At the same time, the metal powder is inserted into the arc where it is molten. A substance-to-substance bond is created between the filler material and the base material during solidification. The process is highly controlled, allowing for precise and localized application of coating. The coating thickness can vary depending on the application requirements.
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