Effect of Flame Spray Deposition Parameters on The Microstructure of Al2 O3 - 13 %TiO2 Coatings Applied Onto 7075 Aluminum Alloy

In this work, the effect of flame spraying parameters on physical, structural and microstructural characteristics of Al2O3 - 13 wt.% TiO2 (AT-13) coatings were studied. NiCrAl and AT-13 feedstock powders were used for spraying a bond coat (BC) and a top coat (TC), respectively, onto a 7075 aluminum alloy substrate. The effect of acetylene-to-oxygen ratio and the spraying distance on surface roughness, crystalline phases, porosity and thickness of top coat were analyzed. The results showed that for the evaluated spraying conditions, the volumetric oxy-fuel ratio had significant effects on roughness, porosity and crystalline phases of the coating. On the other hand, the spraying distance affected the thickness of the coating and did not influence the formation of Al2TiO5 phase; no significant effect of spraying distance on roughness was observed. The results showed that an acetylene: oxygen volumetric ratio of 1:2.5 is preferable to obtain higher melting of the ceramic powders and therefore a denser coating with major content of γ-Al2O3 crystalline phase.

本研究探讨了火焰喷涂（flame spraying）参数对Al₂O₃-13wt.%TiO₂（AT-13）涂层的物理、结构及微观结构特性的影响。实验分别采用镍铬铝（NiCrAl）与AT-13原料粉末，在7075铝合金（7075 aluminum alloy）基体上喷涂制备粘结层（bond coat，BC）与面层（top coat，TC）。分析了乙炔-氧体积比与喷涂距离对面层的表面粗糙度、晶相组成、孔隙率及涂层厚度的影响。结果表明，在所评估的喷涂工况下，乙炔-氧体积比对涂层的表面粗糙度、孔隙率与晶相组成均存在显著影响。另一方面，喷涂距离仅对涂层厚度存在显著影响，且不会影响钛酸铝（Al₂TiO₅）相的生成；未观察到喷涂距离对表面粗糙度存在显著作用。研究结果显示，采用1:2.5的乙炔-氧体积比时，陶瓷粉末熔融程度更高，可获得以γ-三氧化二铝（γ-Al₂O₃）晶相为主要成分的致密度更优的涂层。