Ti45Al8.5Nb合金表面Zr-SiO_(2)复合涂层的制备及其抗高温氧化性能研究

Preparation and High Temperature Oxidation Resistance of Zr-SiO_(2) Composite Coating on Ti45Al8.5Nb Alloy

针对电沉积SiO_(2)涂层在高温氧化过程中易产生裂纹的问题,在SiO_(2)涂层表面磁控溅射Zr沉积层来进行改善。研究表明,Zr沉积层氧化为ZrO_(2)填补了SiO_(2)涂层在烧结时产生的裂纹和孔洞等缺陷,并为SiO_(2)涂层与合金基体的热膨胀系数失配提供了缓冲。此外,氧化过程中形成的ZrO_(2)-SiO_(2)骨架结构提高了涂层结构的稳定性。总体上,Zr-SiO_(2)复合涂层在氧化初期显著抑制了氧向合金基体的扩散以及合金基体元素的外扩散,提高了合金的抗高温氧化性能,经氧化后复合涂层表面的氧化物颗粒明显减少,且氧化膜未出现明显生长。此外,在900℃下经过100 h的恒温氧化后,由于元素互扩散,涂层与基体界面形成了(Ti,Nb)O_(2)/Ti_(5)Si_(3)+Al_(2)O_(3)+Nb_(3)Al/TiN三层扩散层结构,提高了涂层与基体的结合力。

Addressing the issue of crack formation in SiO_(2) coatings during high-temperature oxidation,a supplementary Zr layer was applied onto the SiO_(2) coating surface through magnetic sputtering.This study revealed that the Zr layer,upon oxidation,transformed into ZrO_(2),may effectively amend the cracks and voids that emerged during the sintering process of the SiO_(2) coating.Furthermore,it mitigated the thermal expansion coefficient(TEC)disparity between TiAl and SiO_(2) coatings.In addition,the ZrO_(2)-SiO_(2) skeleton structure formed during the oxidation process may be able to improve the stability of the coating structure.The resultant Zr-SiO_(2) composite coating significantly impeded oxygen inward diffusion from the ambient environment to the Ti45Al8.5Nb substrate,even the outward diffusion of alloy elements in the early stage of oxidation,which notably enhancing its resistance against high-temperature oxidation.Notably,limited growth of oxide particles was observed on the alloy,with a negligible increase in the thickness of oxide scale.Additionally,following a period of 100-hour oxidation at 900℃,mutual element diffusion from both the substrate and coating led to the formation of a three-layered interdiffusion zone(Ti,Nb)O_(2)/Ti_(5)Si_(3)+Al_(2)O_(3)+Nb_(3)Al/TiN.This interdiffusion zone notably bolstered the bond strength between the composite coating and the Ti45Al8.5Nb substrate.