Thermal Spray Coating Processes

Thermal spray coating technologies are highly versatile, allowing engineering of an almost a limitless number of coatings for an extremely wide range of applications - just a few of which include, protecting jet engine components from high temperatures and oxidation, medical devices such as surgical instruments and orthopedic implants, enhancing wear resistance for agricultural components, and providing electrical insulation or conductivity for electronic devices.

HVOF (High Velocity Oxy-Fuel) & Carbide Coatings

What is HVOF

High-velocity, oxy-fuel, (HVOF) devices are a subset of flame spray. There are two distinct differences between conventional flame spray and HVOF. HVOF utilizes confined combustion and an extended nozzle to heat and accelerate the powdered coating material. Typical HVOF devices operate at hypersonic gas velocities, i.e. greater than MACH 5. The extreme velocities provide kinetic energy which help produce coatings that are very dense and very well adhered in the as-sprayed condition.


Flame Spray

What is Flame Spray?

Flame spray is divided into three subcategories, based on the form of the feedstock material, either powder-, wire-, or rod-flame spray. Flame spray coating utilizes combustible gasses to create the energy necessary to melt the coating material. Combustion is essentially unconfined, in that there is no extension nozzle in which acceleration can occur. Common fuel gases include hydrogen, acetylene, propane, natural gas, etc. The lower temperatures and velocities associated with conventional flame spraying typically result in higher oxides, porosity, and inclusions in coatings.

Electric Wire Arc Spray

Two wires (hence a common term for the process is Twin Wire Arc Spray), are fed into the pistol and electrically charged, one positive and one negative. The wires are forced together and form an electric arc, melting the wire. Compressed air, passing through a nozzle, atomises the molten metal and sprays it onto the work piece. There are three methods of wire feeding, push, pull and push/pull. The higher the current rating of the system, e.g. 350A, 600A etc., the higher the spray rate.
Shot Peaning Process
Shot peening is a cold working process used to produce a compressive residual stress layer and modify the mechanical properties of metals. It entails impacting a surface with shot (round metallic, glass, or ceramic particles) with a force sufficient to create plastic deformation. Peening a surface spreads it plastically, causing changes in the mechanical properties of the surface.

The main benefit of shot peening is the delay or prevention of cracks in highly tensile stressed alloy components.

We can alter these undesirable manufacturing and operational tensile stresses to life enhancing residual compressive stresses therefore extending component life.

The process works by introducing the residual compressive stress in the surface of the component. The compressive stress helps to prevent crack initiation as cracks cannot propagate in the compressive environment generated by peening.


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