Implementation of a Low Cost Monitoring and Control System to a Radial Injection Plasma Spray Process Towards Manufacturing of High-Quality, Consistent Coatings at Improved Efficiency and Lower Cost

Implementation of a Low Cost Monitoring and Control System to a Radial Injection Plasma Spray Process Towards Manufacturing of High-Quality, Consistent Coatings at Improved Efficiency and Lower Cost.

In order to produce plasma sprayed coatings with best economical, technical and environmental qualities several factors need to be taken into consideration. These include properties of the powder feedstock, equipment reliability, optimised process parameters and stability of the spray process. In case of plasma spray guns with conventional and frequently used radial powder feeding configurations, proper and constant powder feeding during spraying plays an important role. Once optimised spray parameters need to be preserved and optimal spray conditions for best coating quality and highest deposition efficiency should be kept constant also during possible changes of the spray parameters, e.g. due to electrode wear, powder quality variations etc. Various spray process monitoring tools available are useful for this purpose; especially if they are cost-effective enough to be adopted by industrial thermal sprayers. In the present work, a conventional 40 kW plasma spray process equipped with a typical radial single point powder feeding was studied with a robust and industrially viable on-line monitoring CDD camera “SprayWatch G” system. The plasma spray torch was run under slightly varying spray conditions typical to normal industrial spraying, the spray process was monitored, and various actions, e.g. powder carrier gas flow rate adjustment, were realized in order to restore the most optimum conditions. Special attention was paid on finding correlations between the temperature, brightness, shape, and direction of the spray plume with the properties, e.g. deposition efficiency and technical properties of the sprayed ceramic coatings.