Plasma spraying

The plasma spraying process uses a DC electric arc to generate a stream of high temperature ionised plasma gas, which acts as the spraying heat source. The coating material, in powder form, is carried in an inert gas stream into the plasma jet where it is heated and propelled towards the substrate. Because of the high temperature and high thermal energy of the plasma jet, materials with high melting points can be sprayed.

Plasma spraying produces a high quality coating by a combination of a high temperature, high energy heat source, a relatively inert spraying medium and high particle velocities, typically 200-300 m.sec -1. However, some air becomes entrained in the spray stream and oxidation of the spray material may occur. The surrounding atmosphere also cools and slows the spray stream. Vacuum plasma (VPS) or low pressure plasma spraying (LPPS) reduces these problems by spraying in vacuum or a low pressure, inert gas environment. Plasma spraying is widely applied in the production of high quality sprayed coatings.



  • Spraying of seal ring grooves in the compressor area of aeroengine turbines with tungsten carbide/cobalt to resist fretting wear.
  • Spraying of zirconia-based thermal barrier coatings (TBCs) onto turbine combustion chambers.
  • Spraying of wear resistant alumina and chromium oxide ceramic onto printing rolls for subsequent laser and diamond engraving/etching.
  • Spraying of molybdenum alloys onto diesel engine piston rings.
  • Biocompatible hydroxyapatite coatings for prostheses.


Aeroengine turbine duct with
a thermal barrier coating 		Aeroengine turbine duct

Surface Engineering at TWI

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