Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course


7.6 Plasma spraying

A number of processes have been developed where particles of coating material are heated to a molten state and projected at a substrate which is relatively cold (<200°C). The density of the coating and the adhesion of the coating to the substrate are controlled by the speed at which the particles impact on the substrate.

A plasma – a superheated gas – is formed by using an inert (unreactive) gas such as argon with a small amount of hydrogen or helium and then applying a high energy electric arc at typically 40 kV. The material for the coating is fed into the gun, as a fine powder, down the powder feed. The powder melts in the plasma and the gas expands rapidly and accelerates the molten droplets to speeds of 250–500 m s−1. The process conditions must be carefully controlled so that the coating adheres well to the substrate. This ensures that any friction and wear causes the coating to wear away rather than peel away from the surface. Ideally, the coatings that are produced have low porosity and good mechanical strength.


Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus