On the Relationship Of Tungsten Composition To Coating Properties

Industry today has an increased awareness of environmental, health, and safety issues.  This, together with recent Nuclear Regulatory Commission changes concerning source material (e.g. thorium) have added complexity in the supply chain of thoriated tungsten commonly used in plasma spray spares. In the interest of a safer and more sustainable work environment Oerlikon-Metco has developed non-thoriated solutions which have been proven to have a longer service life than conventional thoriated spares. This paper reports on the effect, if any, caused by tungsten compositional changes and extended service life in coating properties. Microstructure, coating efficiency parameters, hardness, particle state and in-situ stress are evaluated over the duration of the nozzle, comparing coatings with thoriated and non-thoriated nozzles and electrodes with the same spray parameters