Abstract

When spraying is conducted in the ambient atmosphere, the entrainment of air cools down the plasma jet and affects its expansion. It may also cause the oxidation or the chemical decomposition of the sprayed materials. Inert Plasma Spraying (IPS), generally conducted in argon atmospheres, prevents these phenomena. However, the main drawbacks of IPS in comparison with air plasma spraying are the capital and apparating costs. To reduce the latter by 25 to 30%, nitrogen atmospheres may be used as a substitute for the conventional argon atmosphere. This paper presents a study in which titanium carbide and niobium powders were sprayed in argon and nitrogen atmospheres. Cryogenic cooling of the substrate was used during the spray process. This helps to maintain a low temperature in the chamber, produces thick coatings and allows the use of substrate materials that are sensitive to heat. The adhesion, roughness and microstructure of the coatings produced in both atmospheres are compared as well as their nitrogen content.

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