Technology

How does cold gas spraying work?

Cold gas spraying is the most recent method in the field of thermal spraying. 

In comparison to conventional thermal spray processes, cold gas spraying offers special advantages, because the spraying material is neither fused nor melted during the process. Thus, the thermal influence on the coating and the substrate material is minimized.

The high kinetic energy of the particles and the high degree of deformation during the impact on the substrate that is connected with it, allows the manufacturing of homogenous and very dense coatings. The range of coating thicknesses varies from just a few hundredths of a millimeter up to several centimeters.

There are mainly metallic coatings produced, which physical and chemical properties barely differ from the properties of the base material.

With the latest system technology of Impact Innovations GmbH a process gas - preferably nitrogen or helium - is put into a spray gun with a pressure of up to 50 bar (725 psi) and is heated up to a maximum temperature of 1100 °C (2012 °F) in the gun housing.

The subsequent expansion of the heated and high pressurized gas in a convergent-divergent nozzle down to ambient pressure results in the acceleration of the process gas up to supersonic speed and, at the same time, in the cooling down of the gas to a temperature below 100 °C (373 °F).

The spray powders are injected in the convergent section of the nozzle by using a powder feeding unit and carrier gas and are accelerated to a particle speed of up to 1200 m/s in the main gas stream.

In the highly focused spray jet particles impinge the - in most cases untreated - surface of the component, deform the particles and form a strongly adhesive/cohesive and low-oxide coating.

Learn more in this video:

Particle velocity as a measure of layer quality and efficiency

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The coating particle has hit the component at the minimum speed, creating a firm connection. This "critical speed" is different for each material.
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If the impact speed is higher than the "critical speed", the degree of deformation between the particle and the component is increased. The adhesion mechanism of the layer on the component improves.
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If the impact speed is too high and the "erosion speed" is reached, material is removed. No stratification is possible.
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In order to produce dense and solid layers, the impact velocities of the particles must lie between the "critical speed" and the "erosion speed".
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What can be coated by cold gas spraying?

1Which metals can be used?
Magnesium, aluminum, titanium, nickel, copper, tantalum, niobium, silver, gold and many more.
2Can alloys be used?
The Impact Spray System can be used to process nickel-chrome, bronze, aluminum alloys, MCrAlY's and titanium alloys.
3Is it possible to spray material mixtures?
Yes, it is possible to use a mixture of a hard material and a material with a ductile matrix. For example, metal and ceramics or various composite materials.

Individual Processing

Every single coating material is individually processed. The processing of materials requires an individual adjustment of gas temperature and pressure. The combination of these two physical parameters defines the particle velocity and the quality of the coating. The window of the optimal spray velocity, limited by the critical and the erosion velocity is called “window of deposition“. Inside this window of deposition coating quality is influenced by parameters.

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Products

Renowned companies from all over the world have trusted the Impact Spray systems for years.
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Material

Materials

Every successful cold gas spray application begins with the selection of the right powder.
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