钛合金激光诱导涂层纳米准晶化及磨损行为的研究

Laser cladding and additive manufacturing technologies have been used in the industry fields of the automotive, modern architecture, aeronautics and astronautics. Nevertheless, the comprehensive performance (especially the wear resistance) of the titanium alloys parts that produced by the additive manufacturing still should be improved. The proposed project is based on the property of the rapid solidification of the laser molten pool, Cu-base mixed powders are used to be the nano-quasicrystalline factor, which are added in the pre-melting powders, then the nano-quasicrystalline coatings are deposited on the additive manufacturing titanium alloys substrate by means of the laser-induced process and the in-situ reaction in the high-temperature molten pool, which increase the wear resistance of the substrate without reducing its comprehensive performance. Such coating will be quantitatively analysed, i.e. the microstructure of such coating and the location of the interface between the coating and substrate will be researched; the content of the nano-quasicrystalline phases, the induced nano-quasicrystalline actions of the laser beam to such coating, the influencing disciplinarian of the microstructure evolution to the nano-quasicrystalline tendency and the tribological properties of such coating will be revealed; an inherent relation of the laser molten pool rapid freezing, the characteristics of the nano-quasicrystalline factor, and the quasicrystalline forming of the substrate surface will be explored; the mechanisms of the nano-quasicrystalline tendency and wear resistance of such coating will be revealed. This research provides a new research approach to explore the multiphase and also improve the performance of the additive manufacturing titanium alloys, which owns the important theoretical significance and research value to expand the additive manufacturing technology and accelerate the process of the lightweight materials.

激光熔覆与增材制造技术已被应用于汽车、现代建筑及航空航天等工业领域，但增材制造所形成钛合金零部件的综合性能（特别是耐磨性）仍有待提高。本项目提出基于激光熔池快速冷凝特性，所采用Cu基混合粉末为纳米准晶化因子，将其添加于预熔粉末中，经激光熔覆诱导处理，辅助高温熔池中原位生成反应，在增材制造钛合金基材表面制备纳米准晶化涂层，可在不降低基材综合性能的基础上提高其耐磨性。对该纳米准晶化涂层进行定量分析，研究涂层及其与基材之间界面附近的微观组织结构，揭示涂层中纳米准晶相含量、激光束对涂层的诱导纳米准晶化行为、组织结构演变对纳米准晶化及耐磨性的影响规律，寻求激光熔池急冷、纳米准晶化因子特性与基材表面准晶化的内在联系，阐明激光熔覆涂层纳米准晶化及耐磨机理。该研究将为增材制造钛合金多物相性探索及性能改善提供一条新颖的研究思路，对扩展增材制造技术、加速材料轻量化进程具有重要的理论意义与研究价值。

增材制造及激光熔覆技术已被应用于高端装备制造、现代建筑及航空航天等工业领域，但增材制造钛合金工业零部件的综合性能仍需进一步改善。准晶结构与晶体及非晶体有本质区别，准晶具有许多理想特性，如硬度高、摩擦系数低及抗高温氧化性好等；纳米材料基于其良好韧性、高强度及硬度等特性在钛合金增材制造领域具有非常巨大的应用潜力。本课题基于激光熔池高速冷凝特性，部分合金混合粉末则为纳米准晶化因子，将其添加于预熔粉末中，经激光熔覆诱导处理，凭借高温熔池中原位生成反应，在增材制造钛合金基材表面制备纳米准晶化涂层，可在不降低基材综合性能的基础上极大改善其耐磨性。课题分析涂层中纳米级准晶相与非晶相的相互作用机理，涂层内气孔生成、脆性相析出、粉末未熔化、微裂纹萌生及纳米准晶相的形成原因。研究表明，纳米准晶化因子添加即对增材制造钛合金激光熔化沉积复合材料进行改性处理，使增材制造钛合金表面磨损体积低于基材的1/6；纳米晶不仅镶嵌于非晶相上，也分布于晶化相中，激光熔化沉积复合材料为非晶、纳米晶及其它晶化相共存，并证实二十面体准晶相存在于该复合材料中；结合所制备复合材料的功能梯度特性，深入研究沉积层界面的组织形态、准晶微观结构演变规律及纳米准晶化材料的形成机理。研究表明，所制备复合材料中准晶多趋于多面体结构，其形貌反映了点群对称性；即使在准晶呈珊瑚状形貌时，其外形也是由许多小平面构成；准晶在激光熔池中是均匀形核的，在多数情况下先于晶体析出，晶粒尺寸普遍较小，甚至可达纳米级别；揭示涂层中纳米准晶相含量、激光束对涂层的诱导纳米准晶化行为、组织结构演变对纳米准晶化及耐磨性的影响规律。本课题所完成内容为增材制造钛合金多物相性探索及性能改善提供了一条新颖的研究思路，将对促进我国激光增材制造产品质量升级、加速材料轻量化进程具有重要的实际应用价值及理论意义。