SiO2添加剂对等离子喷涂Al2O3涂层抗热震性的影响

Influence of Additive SiO2 on Thermal Shock Resistance of Plasma-sprayed Al2O3 Coating

关键词:  等离子喷涂  陶瓷涂层  热震性  添加剂

Key words:  plasma-spray  ceramic coating  thermal shock resistance  additive

摘要:

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。

Abstract:

The influence of additive SiO₂ with different content on the thermal shock resistance of plasma-sprayed Al₂O₃ 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%AiO₂ into the plasma-sprayed Al₂O₃ coating.The reasons are that the suitable content of SiO₂ 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 Al₂O₃+3% SiO₂ coating is increased remarkably.But a surfeit of SiO₂ is subject to cause stress concentration and to produce coarsing crack, because of obvious difference between the thermal expansion coefficient of Al₂O₃ and that of SiO₂.And, the thermal shock resistance is on the decrease when the gas hole rate increases largely.