Axial Suspension Plasma Sprayed Titanium Oxide Coatings

Titanium oxide is well known for its remarkable physical, chemical and electrical properties. Coatings of titania have found quickly a wide range of applications, self-cleaning and photocatalytic surfaces being two of the applications with large industrial interest. Anatase is the phase that is preferred for such applications as it has best photoactivity, hence finding the right phase ratio in coatings is often a demanding task. Axial Suspension Plasma Spraying (ASPS) combines the benefits of solid powder plasma spraying (large coatings areas) with the special microstructural features and properties given by the nano- or submicrometric feedstock material.

In this study, several feedstock materials were used to produce thin TiO2 coatings. The spraying method was ASPS and all investigation were done on as-sprayed samples. Microstructure evaluation was done by SEM and coating porosity was measured by both Image Analysis and Water Impregnation. The coatings adhesion was tested according to ASTM-C633 and the phase composition evaluated by XRD. Surface roughness and the hardness of the coatings was measured as well. The main results are discussed in correlation with spray parameters and powder size influence on the phase content/ratio in coatings and the best coating structure is proposed.