Department of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, PR China.
Department of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, PR China.
Ultrason Sonochem. 2019 Dec;59:104742. doi: 10.1016/j.ultsonch.2019.104742. Epub 2019 Aug 22.
To broaden the scope of non-aerospace applications for titanium-based alloys, both hexagonal C40 binary TaSi and ternary Al alloyed TaSi nanocrystalline coatings were exploited to enhance the cavitation erosion resistance of Ti-6Al-4V alloy in acidic environments. To begin with, the roles of Al addition in influencing the structural stability and mechanical properties of hexagonal C40 Ta(SiAl) compounds were modelled using first-principles calculations. The calculated key parameters, such as Pugh's index (B/G ratio), Poisson's ratio, and Cauchy pressures, indicated that there was a threshold value for Al addition, below which the increase of Al content would render the Ta(SiAl) compounds more ductile, but above which no obvious change would occur. Subsequently, the TaSi and Ta(SiAl) coatings were prepared and their microstructure and phase composition were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Both the two coatings exhibited a uniform thickness of 15 μm and a densely packed structure mainly composed of spherically shaped nanocrystallites with an average diameter of about 5 nm. Nanoindentation measurements revealed that Al alloying reduced the hardness (H) and elastic modulus (E) values of the TaSi coating. Ultrasonic cavitation erosion tests were carried out by immersing coated and uncoated samples in a 0.5 M HCl solution. The cavitation-erosion analysis of the tested samples was investigated by various electrochemical techniques, mass loss weight and SEM observation. The results suggested that both coated samples provided a better protection for Ti-6Al-4V against the cavitation-erosion damage in acidic environments, but the addition of Al further improved the cavitation-erosion resistance of the TaSi coating.
为了拓宽钛基合金在非航空航天领域的应用范围，本研究分别采用六方 C40 二元 TaSi 和三元 Al 合金化 TaSi 纳米晶涂层来提高 Ti-6Al-4V 合金在酸性环境中的抗空蚀性能。首先，采用第一性原理计算对 Al 加入影响六方 C40 Ta(SiAl)化合物结构稳定性和力学性能的作用进行了建模。计算的关键参数，如 Pugh 指数（B/G 比）、泊松比和 Cauchy 压力表明，Al 加入存在一个阈值，低于该值时，增加 Al 含量会使 Ta(SiAl)化合物更具延展性，但高于该值时，不会发生明显变化。随后，制备了 TaSi 和 Ta(SiAl)涂层，并通过 X 射线衍射（XRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）对其微观结构和相组成进行了表征。两种涂层均具有 15 µm 的均匀厚度和主要由球形纳米晶组成的致密结构，纳米晶的平均直径约为 5 nm。纳米压痕测量表明，Al 合金化降低了 TaSi 涂层的硬度（H）和弹性模量（E）值。通过将涂覆和未涂覆的样品浸入 0.5 M HCl 溶液中进行超声空蚀腐蚀试验。采用各种电化学技术、质量损失重量和 SEM 观察对测试样品的空蚀分析进行了研究。结果表明，两种涂层都为 Ti-6Al-4V 提供了更好的保护，使其在酸性环境中免受空蚀损伤，但 Al 的加入进一步提高了 TaSi 涂层的抗空蚀性能。
