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Institute of Energy and Climate Research

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Thermal Spraying

Thermal spraying involves injecting particulate raw materials in the form of powders or suspensions into a hot gas torch, melting them, and accelerating them towards the substrate. A multitude of process parameters, such as gas composition, gas flow, current, spraying distance, particle size distribution, carrier gas flow, ambient pressure etc. influence the degree of melting and the velocity of the particles and thus significantly affect the resulting microstructure, adhesion, and stresses.

The properties of the hot gas and the particles in flight can be analysed to result in a better understanding of the processes and to ensure quality.

Atmospheric plasma spraying of a ceramic thermal barrier coat on a turbine blade

Plasma spraying

Plasma spraying involves melting particle-shaped raw materials and accelerating them towards the substrate by means of a plasma beam produced by ionizing a gas stream.

Atmospheric plasma spraying (APS) is especially suitable for depositing ceramics, in particular oxide ceramics for thermal barrier coatings.

Burners: Triplex II, TriplexPro-210, Axial III, F4, 9MB, F100 Connex (inner coatings)

Suspension plasma spraying (SPS) is an APS process which involves a liquid suspension as a precursor. This permits the processing of particles in the sub-micrometre range and thus leads to novel, microstructured layers.

Burners: Triplex II, TriplexPro-210, Axial III

Low-pressure plasma spraying (LPPS) and vacuum plasma spraying (VPS) permit ceramic and especially also metallic layers to be produced, while oxygen uptake is avoided.

Burners: F4, TriplexPro-200, O3CP

Low-pressure thin-film plasma spraying (LPPS-TF) represents a further development of vacuum plasma spraying conducted at low pressure. It enables thin, gas-tight layers to be deposited.

Burners: F4, TriplexPro-200, O3CP

Plasma spraying physical vapour deposition (PS-PVD) also takes place at low pressure, but at increased power. With the appropriate powders, depositing novel, columnar structures is possible even from the vapour phase.

Burner: O3CP

Gas dynamic cold spray

Gas dynamic cold spraying involves expanding a moderately pre-heated, compact gas through a de Laval nozzle, which results in very high velocities in the supersonic range. If the powder particles achieve a critical velocity (dependent on the material) they are plasticized upon impacting the substrate, and a firmly adhering, dense coat results. This method is especially suitable for oxidation-sensitive materials.

System: Kinetiks 8000

High-velocity flame spraying

In contrast to plasma spraying, high-velocity flame spraying permits significantly higher particle velocities at comparatively moderate temperatures of the hot gas torch. This means that the process is particularly suitable for wear-resistant alloys and MCrAlY bond coats.

Burners: DJ2600, DJ2700, Hybrid Aircap

Hydrogen-/methane-oxygen process with Air/N2 shroud gas