Development of Ceramics and/or FGM Coatings Used in Slurry Erosion-Corrosion Environment

研究了低压等离子喷涂（LPPS）和激光热喷涂（LTP）制备的陶瓷和/或功能梯度材料涂层的浆液侵蚀性能。分别以硅砂浆、石膏浆、粉煤灰浆和石膏-粉煤灰浆为试验材料，采用缝内射流和旋转试验装置进行了砂浆侵蚀试验。在缝内射流型和试样旋转型装置中，浆体浓度分别控制在30 wt%和60 wt%。试件设计为圆盘型和叶轮模拟。试验结果表明，喷涂条件和其他处理条件对涂层的耐冲蚀耐久性有较大影响。例如，底涂、密封、热处理和降压条件。浆液侵蚀试验表明，试样表面侵蚀区域不同，其抗侵蚀特性也不同。这种现象可能是由于单个浆料颗粒沿试样表面攻击的影响，即使浆料射流以正常的角度撞击。本研究还对浆体颗粒的冲击角度、冲击频率（浓度）进行了实验和理论计算。在料浆环境条件方面，硅砂料浆最不利，粉煤灰料浆次之，石膏料浆最差。腐蚀试验表明，密封处理提高了其耐蚀性，但与浆液侵蚀耐久性无关。

In this study, the properties of slurry erosion of ceramics and/or functionally gradient materials coatings formed by low-pressure plasma spraying (LPPS) and laser thermal spraying (LTP) were assessed. Slurry erosion tests were carried out by the jet-in-slit type and the specimen-rotating type apparatus using silica sand slurry, gypsum slurry, fly ash slurry, and gypsum-fly-ash slurry respectively. The slurry concentrations were controlled at 30 wt% in the jet-in-slit type and 60 wt% in maximum in the specimen-rotating type apparatus respectively. Specimens were designed as disk type and the mock of impellers.The test results showed that the durability of coatings to erosion was strongly influenced by the conditions of spraying and other treatments. for instance, under-coating, sealing, heat treatment and pressure lowering conditions.Slurry erosion test revealed that the erosion-resistance characteristics differed depending on the erosion areas on the specimen surface. Such phenomena may be attributed to the influence of attack by individual slurry particles along the specimen surface, even though the slurry jet impacted at normal incidence. The impact angles, impact frequencies (concentration) of slurry particles were also calculated experimentally and theoretically in this study. As for the conditions of slurry environment, silica sand slurry is most adverse one, then fly ash is at the second, and gypsum one is at the last rank.Corrosion test showed that sealing treatment improved corrosion resistance it although has nothing to do with slurry erosion durabilities.