The graph plots the energy content, or enthalpy, of the gases as a function of temperature. It can be seen that argon and helium exhibit higher temperatures, whereas nitrogen and hydrogen exhibit higher enthalpies. Therefore, combinations of these gases can produce the required temperature, enthalpy, and gas velocity.
Direct-current, plasma arc spray is the most flexible of the thermal spray processes with respect to materials that can be sprayed, because of the inert gases, high gas velocity, and extremely high temperatures and energies. Plastic/polymers, metals and alloys, and ceramics can all be sprayed using plasma spray. Plasma arcs can be used for applying coating, creating free-standing shapes (near-net fabrication), and materials processing, for example, spheroidization.
Volume 5A, Thermal Spray Technology ⇒ Thermal Spray Processes and Coatings ⇒ Thermal Spray Processes
