TWI Frequently asked questions
by Suman Shrestha
The disadvantages associated with plasma spraying include:
- Air plasma spraying equipment tends to require more investment than arc and flame spraying. Equipment used for vacuum plasma, or low-pressure plasma, and controlled atmosphere plasma spraying has a very high capital cost. These areprobably the most expensive thermal spraying processes.
- It is a line-of-sight process, similar to all other thermal spraying processes, making it difficult to coat internal bores of small diameters or restricted access surfaces.
- The plasma spray gun usually experiences rapid deterioration of the inner gun electrodes and other internal components. This leads to frequent replacement of gun electrodes, and the need for quality control to maintain coatingconsistency.
- The high temperatures associated with the plasma jet can result in carbide decomposition or excessive oxidation when spraying in air, giving carbide coatings with lower hardness or metallic coatings with higher oxide levelscompared with HVOF sprayed coatings.
- The equipment is not suitable for manual operation and requires use of automated gun manipulators.
