316L不锈钢表面等离子喷涂TiO2-10Al2O3热障涂层组织和电热性能分析

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

为了提高316L不锈钢表面等离子喷涂TiO2涂层的性能,通过添加Al2O3颗粒的方式制备TiO2-10Al2O3复合热障涂层。采用X射线衍射(XRD)、扫描电镜(SEM)、热重、电热等试验测试分析其性能。研究结果表明:TiO2-10Al2O3涂层产生了六方结构TiO2相。在涂层表面形成了熔融区与未熔融区两个部分,颗粒在熔融区中呈现充分铺展,形成了紧密结合效果。涂层形成了致密组织,并未产生纵向分布的裂纹,当把Al2O3添加到TiO2中之后,可以使复合涂层达到更加紧密的结合状态。当加入Al2O3颗粒后,试样氧化增重速率减小。当温度上升后,涂层发生了电阻率线性增加的变化现象,不同循环周期中的增长斜率基本一致。涂层形成较为完整的结构,并未产生明显裂纹与氧化区,依然保持致密组织结构,具备优异电热稳定性。

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.