B&B Coatings | Huddersfield

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Thermal Spray Process

Thermal Spray Process

Thermal Spray Coatings can dramatically improve the perfomance of a wide range of materials, particularly hardness and wear resistance.

What is Thermal Spraying? 

Thermal spraying is a technology which improves or restores the surface of a solid material. The process can be used to apply coatings to a wide range of materials and components, to provide resistance to: Wear, erosion, cavitation, corrosion, abrasion or heat.

Thermal spraying is also used to provide electrical conductivity or insulation, lubricity, high or low friction, sacrificial wear, chemical resistance and many other desirable surface properties. 

Thermal spraying is widely adopted across many industries as a preferred method. It has huge scope to extend the life of new components or through the use of tried and tested techniques, to repair and re-engineer worn or damaged components

The Basics 

All methods of thermal spraying involve the projection of small softened particles onto a cleaned and prepared surface where they adhere to form a continuous coating. Combined thermal and kinetic energy causes the particles to flatten or ’splat’ onto the surface to produce a cohesive coating of successive layers. 

  • Despite the name it is Metallurgically cold process -Virtually no heat input to the substrate (<80˚C typically) 
  • As there is no significant input of heat to the substrate material it causes very little distortion. 
  • Primarily a mechanical bonding process. 
  • Can be used to apply many materials: Steels, stainless steels, nickel alloys, copper, bronzes, molybdenum, ceramics, tungsten carbides etc. 
  • Can be applied at various thicknesses, typically 100-750 microns but can be more. 

There are four main types of Thermal Spraying

B&B Coatings offer Powder Flame Spray and HVOF

Flame Spray

Gas fuel and oxygen are mixed and ignited to produce a flame. The material, either a wire or powder is fed into the flame. For wire flame spray, the material is melted and the compressed air, passing through a spray nozzle atomises the molten metal and sprays it onto the work piece. The larger the wire diameter, the higher the spray rate. For powder flame spray, the powder particles (metal or ceramic ) are softened in the flame and the speed of the flame gases through the nozzle sprays the softened powder onto the work piece.

HVOF

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.

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