The damaging of the electrodes during spraying can affect the reproducibility of the plasma spray process. Indeed, this may influence the plasma characteristics and the energy transfer to the sprayed particles resulting in significant changes in the coating attributes. In this paper, results from a detailed investigation on the stability of plasma spraying are presented. Specifically designed diagnosis tools were used to study the evolution of key parameters of a plasma spray process during a long-term experiment. A comprehensive analysis is carried out on the collected set of data, with an emphasis on the correlation that may exist among them. Results show significant variations in the particle state and gun characteristics with the spraying time. These variations are reflected in the microstructure of the sprayed coatings. The investigation also gives some indication on how the spray process could be controlled.