The metal spraying process
The process basics
All methods of thermal spraying involve the projection of small molten or softened particles onto a prepared surface where they adhere and form a continuous coating. To create the molten particles, a heat source, a spray material and an atomisation/projection method are required. Upon contact, the particles flatten onto the surface, freeze and mechanically bond, firstly onto the roughened substrate and then onto each other as the coating thickness is increased.Materials, accessories and automation
- Flame Spray Equipment
- Arc Spray Equipment
- Plasma Spray Equipment
- HVOF Spray Equipment
- Materials & Accessories
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Gas fuel* and oxygen flame (*commonly propane or acetylene)
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Wire or powder or ceramic rods
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Compressed air (wire flame)
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The 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.
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Electric arc
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Wire
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Compressed air
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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, 700A etc., the higher the spray rate.
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Plasma arc
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Powder (ceramic, metal, plastics)
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Via plasma jet
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Plasma is the term used to describe gas which has been raised to such a high temperature that it ionises and becomes electrically conductive. In the case of Plasma spraying, the plasma is created by an electric arc burning within the nozzle of a plasma gun and the arc gas is formed into a plasma jet as it emerges from the nozzle. Powder particles are injected into this jet where they soften and then strike the surface at high velocity to produce a strongly adherent coating. The work piece remains cool because the plasma is localised at the gun.
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Fuel (liquid or gas) and oxygen flame
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Powder (metal)
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Via the flame
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The fuel (liquid kerosene in our system) is mixed with oxygen and ignited. The combustion gases pass through a converging/diverging nozzle and accelerate to around 1,500m/sec. The powder is injected into the accelerated flame where it softens and gathers speed. The high impact speed of the particles produce a highly adherent, dense coating structure.
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Metallisation stock and supply a wide range of the most common thermal spray materials including wires and powders. Please review our materials section for our full range.
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Metallisation stock and supply a wide range of thermal spray accessories to assist in the smooth running of equipment as well as sealers, masking products etc. For a sample of our accessories, please view our accessories section or contact Metallisation if we are not displaying your required items and we will endeavour to help.
