强流脉冲离子束辐照钛合金表面光滑化及耐磨抗蚀复合强化机理研究

Titanium alloys are widely used in aerospace application and biomedical device for structural materials, however, they are also characterized by low hardness, poor tribological property as well as low load bearing capacity, which have hindered their service life under the alternating load such as friction, vibration and tension. Furthermore, titanium is very sensitive to filiform corrosion in the chloride containing solutions with higher temperature, which restricted its widespread application as a biomedical material. Surface modification technologies associated with titanium alloy do not meet the requirement for the improvement in combined properties. Furthermore, process of these technologies is usually complicated, and the modification effect is restricted. In the present research, high-intensity pulsed ion beam (HIPIB) is used to directly irradiate titanium alloy in order to improve the wear and corrosion resistance and obtain smooth modification surface. The purpose of this item is to open up a new energetic beam surface modification technology for titanium alloys, conquering the shortcoming in terms of process complexity, low processing efficiency and surface roughening, achieving large-area, high-efficiency and smooth combination modification. Based on the microstructural analysis results of modified layer, understanding the combination modification mechanism of titanium alloys under the coupled thermal-dynamic effects induced by HIPIB.

钛合金系航空航天、生物医用等领域中应用的重要金属结构材料。然而，较低的硬度和承载能力以及较差的摩擦学性能限制了其在伴有摩擦、振动或拉伸等交变载荷下的安全使用寿命。此外，在具有较高温度的含氯溶液中，钛对丝状腐蚀的敏感性大大增强，这尤其限制了其作为生物医用材料的广泛应用。目前基于钛合金的表面改性技术主要针对钛合金单一性能的改善，且工艺复杂、改性效果有限。本项目利用强流脉冲离子束技术，开展直接辐照钛合金表面光滑化及耐磨抗蚀复合改性研究。旨在发展出一种钛合金载能束表面改性新技术，克服其它载能束表面改性技术工艺复杂、加工效率低及表面粗糙化的缺点，实现钛合金大面积、高效率耐磨抗蚀表面光滑化复合改性。最终弄清在强流脉冲离子束辐照热-力耦合作用下，钛合金耐磨抗蚀及表面光滑化复合改性机理。

钛合金系航空航天、生物医用等领域中应用的重要金属结构材料。然而，较低的硬度和承载能力、较差的摩擦学性能和抗腐蚀性能限制了其在伴有摩擦、振动或拉伸等交变载荷和腐蚀介质下的安全使用寿命。本项目利用强流脉冲离子束技术，开展直接辐照钛合金表面光滑化及耐磨抗蚀复合改性研究。结果表明，HIPIB辐照钛合金表面形成了以局部烧蚀坑和熔融扰动为主要特征的烧蚀形貌，表面粗糙度随着辐照次数的增加呈现先增加后减小的可控光滑化特征。原始钛合金试样表面粗糙度为0.086，经HIPIB 5次辐照后表面粗糙度降为0.06。原始试样存在(401)衍射峰，辐照后试样表面的(401)衍射峰消失，表明高能量密度沉积的快速熔凝效应使得表层原子结构发生了改变，同时， HIPIB辐照导致了衍射峰向高角偏移和宽化，表明了辐照试样改性层产生了压缩应力和显微结构的细化。原始试样的显微硬度为3.7 GPa左右，磨损率为0.22 mg/min左右，辐照5次后，硬度增加到约4.4 GPa，磨损率降低到约0.08 mg/min，这主要归因于HIPIB的快速熔凝导致改性层显微结构明显细化。此外，辐照产生的应力波和冲击波造成的加工硬化也是使钛合金表面硬度增加的重要原因。原始钛合金的开路电位为-500 mV左右，辐照后钛合金开路电位提高到-100 mV左右，提高约400 mV。动电位极化曲线表明，被辐照试样具有明显优于原始试样的抗蚀性能，表现为腐蚀电位的显著提高和腐蚀电流密度的降低。电化学阻抗谱表明，原始及辐照试样均表现为容抗弧，且辐照后试样的容抗弧直径显著增大，表明电极反应阻力增大，电极腐蚀速率减小，抗腐蚀性能增强。辐照后钛合金抗腐蚀性能的改善主要归因于被辐照表面显著的晶粒细化、化学成分的均匀化和显微结构致密化以及有害相的选择性烧蚀。