SiO_2添加剂对等离子喷涂Al_2O_3涂层抗热震性的影响

Influence of Additive SiO 2 on Thermal Shock Resistance of Plasma-sprayed Al 2O 3 Coating

通过在Ａｌ２Ｏ３陶瓷粉末中添加不同数量的ＳｉＯ２，探讨其对等离子喷涂涂层抗热震性的影响。结果表明，在等离子喷涂Ａｌ２Ｏ３涂层中添加３％ＳｉＯ２后，热震起裂次数及热震失效次数均得到明显提高。其原因是适量ＳｉＯ２，能明显增加Ａｌ２Ｏ３涂层中的气孔和微裂纹。气孔尺寸均匀，直径在１～２μｍ以内，微裂纹以细网状分布于涂层薄片内。在热震过程中，气孔与微裂纹缓解涂层内应力，延缓了裂纹的扩展，故能显著提高涂层的抗震性能。但添加过量ＳｉＯ２后，由于Ａｌ２Ｏ３与ＳｉＯ２热膨胀系数差异过大，易造成应力集中，产生粗大裂纹，另外，气孔率过大，降低了抗热震性能。

The influence of additive SiO 2 with different content on the thermal shock resistance of plasma-sprayed Al 2O 3 coating was investigated. The experimental results have shown that the thermal shock lifetime of the plasma-sprayed coating and the lifetime of plasma-sprayed coating before coating failure were increased obviously when adding 3%AiO 2 into the plasma-sprayed Al 2O 3 coating. The reasons are that the suitable content of SiO 2 in the coating makes the gas holes and microcracks in the coating increase remarkably and the size of the gas holes be uniform and most of them be within 1～2μm in diameter and microcracks well-distribute in the coating films. This pattern of gas hole and microcrack can release internal stress in the coating and decrease the coating elastic moduel, so the thermal shock resistance of Al 2O 3 +3% SiO 2 coating is increased remarkably. But a surfeit of SiO 2 is subject to cause stress concentration and to produce coarsing crack, because of obvious difference between the thermal expansion coefficient of Al 2O 3 and that of SiO 2. And, the thermal shock resistance is on the decrease when the gas hole rate increases largely.