Microstructures and Electrothermal Properties of 316L Stainless Steel Surface-Modified with Plasma-Sprayed TiO₂-10Al₂O₃ Coatings

316 L stainless steel surfaces were modified with TiO₂-10 Al₂O₃ composite thermal barrier coatings deposited by plasma spraying.The influence of the doping of Al₂O₃ powder on the microstructures and electro-thermal behavior was investigated with X-ray diffraction(XRD),scanning electron microscopy(SEM) and thermogravimetry(TG).The results show that the Al₂O₃-doping made the difference.To be specific,hexagonal phased TiO₂ dominated; fully-melt compact TiO₂ areas co-existed with partly-melt highly porous TiO₂ grains on the TiO₂-10 Al₂O₃ coatings and neither longitudinal crack nor oxidation zone was observed.The Al₂O₃-doping significantly increased the compactness and decreased the oxidization weight gain-rate because of the increased thermal and electrothermal stability. In addition,as the temperature increased,the resistivity of the TiO₂-10 Al₂O₃ coating linearly increased at an increase-rate independent of the heating cycle.Possible mechanisms responsible for the enhanced electrothermal stability were also tentatively discussed in a thought provoking.