Engineering Demands of Thermal Spray Coating

The demands for thermal spray coating are becoming more and more stringent. Environmental concerns are also being considered as an integral part of the design process. For future economic competitiveness and a lower environmental impact, we must, therefore, turn our attention to processes that use the minimum of resources. Thermal spraying is an attractive coating technique as it offers a wide choice of materials and processes that have a reduced impact on the environment when compared to conventional plating processes.

Thermal spray coating techniques

Techniques such as HVOF, flame wire spraying, flame powder spraying, arc wire spraying, plasma spraying, and cold gas spraying, allow many problems of wear, corrosion and thermal degradation to be resolved by engineering the surface with tailor-made coatings.

In the simplest terms possible, thermal spray coating involves heating a material in powder or wire form to a molten or semi-molten state. The material is propelled using a stream of gas or compressed air to deposit it, creating a surface structure on a given substrate. The coating material may consist of a single element but is often an alloy or composite with unique physical properties that are only achievable through the thermal spray process. Thermal spray coating processes involve the deposition of coatings from a stream of high velocity finely divided particles in a molten or semi-molten state impinging onto the substrate. These processes use fine powdered source material or sometimes metal wire that is molten and broken into fine droplets. The coating gun adds thermal energy to bring the materials to a plastic or molten condition and accelerates these materials at high velocities toward the substrate.

There are several different types of thermalspray coating processes. They differ in how they apply thermal and kinetic energy to the source material, the form of the source material and the relative velocities and temperatures of the flame. Each process has advantages and disadvantages, and some are optimized for certain types of coatings.

Thermal Spray Coating Technology

Coating material starts as powder or wire form. A wide range of materials is available. The thermal spray gun provides energy to the coating material particles and transports the coating to the substrate part. Energy can be thermal (heat) or kinetic (velocity). Several different technologies are available: HVOF, Plasma Spray, Flame Spray, The thermal spray gun is controlled by an industrial robot for precise repeatable control of the coating. As the particles of molten material impact the substrate, they collapse into flattened droplets and in lamellar layers forming a cohesive coating structure. Cooling of the substrate is used to control the temperature gain of the substrate.

The thermal spray gun is controlled by an industrial robot for precise repeatable control of the coating. As the particles of molten material impact the substrate, they collapse into flattened droplets and in lamellar layers forming a cohesive coating structure. Cooling of the substrate is used to control the temperature gain of the substrate.