激光熔覆制备人工关节面纳米陶瓷涂层的成形机理及其摩擦学行为研究

Titanium alloy is the preferred material of artificial joints because of its excellent biocompatibility and biomechanical properties. However, the wear resistance of titanium alloy articular facet can’t meet the long service life requirement of artificial joint. Thus, a crucial problem to be solved urgently in the field of artificial joint manufacturing is how to fabricate excellent articular facets with good wear resistance. One of most efficient approaches to enhance the tribological properties is to fabricate a wear-resistant ceramic coating on the articular facets of titanium alloy artificial joint. In this project, the rapid melting and solidification characteristics of laser cladding are utilized to regulate the crystal-grain growth during the formation of ceramic coating for the purpose of preparing nano-ceramic coatings with excellent tribological properties on the articular facets of titanium alloy artificial joint.. The rapid melting and solidification behaviors of nano-ceramic particles under laser cladding process are investigated, and the growth model of nano crystal-grain during the formation of ceramic coating is established. The construction principles of continuous liquid phase in the laser cladding process of ceramic coatings are studied, and the densification mechanisms of nano ceramic coating are demonstrated. The microstructure evolution laws of nano-ceramic coatings are researched, and the formation mechanisms of the wear resistance properties of nano-ceramic coatings are revealed. The friction and wear properties of the nano-ceramic coatings on the articular facets of artificial joint under typical biological service condition, such as simulated body fluids, are investigated; and the influences of the process parameters of laser cladding on the tribological properties of nano-ceramic coatings are analyzed. Through the implementation of this project, we hope to establish a method to prepare high-performance nano ceramic coatings with excellent wear resistance on the articular facets of artificial joint by laser cladding.

钛合金因其优异的生物相容性和生物力学性能，成为人工关节的首选材料。但钛合金关节面的耐磨性不能满足人工关节的长寿命要求，如何制备出耐磨性能优异的关节面是亟待解决的关键问题。在钛合金关节面上制备耐磨涂层是解决该问题的有效途径。本项目提出利用激光熔覆的快速熔凝特点调控陶瓷涂层成形过程中晶粒生长，以期在钛合金人工关节面上制备出具有优异摩擦学性能的纳米陶瓷涂层。.研究激光作用下纳米陶瓷颗粒的快速熔化与凝固行为，建立陶瓷涂层成形过程中的纳米晶粒生长模型；研究陶瓷涂层激光熔覆成形过程中持续液相构建原理，揭示纳米陶瓷涂层的致密化机理；研究纳米陶瓷涂层微观结构的演变规律，查明陶瓷涂层耐磨功能的形成机制；研究人工关节面纳米陶瓷涂层在模拟体液等典型生物服役环境下的摩擦磨损性能，揭示激光制备工艺条件对纳米陶瓷涂层摩擦学性能的影响规律。通过本项目的实施，建立起一种激光制备高性能人工关节面纳米陶瓷耐磨涂层的方法。

钛合金关节面的耐磨性不能满足人工关节的长寿命要求。本项目利用激光熔覆的快速熔凝特点调控陶瓷涂层成形过程中晶粒生长，在钛合金人工关节面上制备出了具有优异摩擦学性能的TiC、TiN、TiB等生物陶瓷涂层。主要研究内容和结果如下：.开发了面向耐磨生物陶瓷涂层的超声辅助激光熔覆系统，建立了适用于不同光斑能量密度分布模式下的瞬态温度场模型和接近实际的激光熔化纳米陶瓷颗粒的熔池模型，查明移动激光束条件下的熔池的三维瞬态温度场、温度梯度和冷却速率的分布和变化规律，提出了减小熔覆层间的温度梯度从而使温度分布和冷却速率均匀化的激光输入能量的调节策略，获得了激光熔覆工艺参数对陶瓷涂层成形质量的影响规律。.研究了激光熔覆过程中持续液相与纳米陶瓷颗粒的相互作用过程，在激光熔覆制备陶瓷涂层工艺中添加SiO2颗粒作为液相引入，观测到在待熔覆区域中SiO2颗粒形成了持续液相并存在五个连续的特征区域，依靠毛细管力、粘性流动和纳米效应，发现SiO2液相辅助激光熔覆工艺过程的作用机理是基于液相烧结与完全熔化/凝固两种机制，揭示了持续液相与纳米陶瓷颗粒的接触与致密、空洞的闭合机制，有效实现了初始纳米陶瓷颗粒的重排和陶瓷涂层晶粒致密化。.研究了激光作用下纳米陶瓷颗粒的熔化与凝固行为，建立了陶瓷涂层成形过程中的纳米晶粒生长模型，发现激光熔覆通过快速熔凝细化晶粒尺寸；查明了不同熔覆条件下稀土氧化物纳米第二相含量、分布对纳米陶瓷涂层晶粒尺寸、力学性能等方面的影响规律，研究了纳米陶瓷涂层在模拟生理环境条件下的摩擦磨损机理、减摩特性和抗磨损特性等摩擦学性能，构建了陶瓷涂层的工艺参数—生物耐磨性能一体化模型，揭示了激光制备工艺条件对纳米陶瓷涂层摩擦学性能的影响规律。制备的陶瓷涂层微观组织均匀致密，与基体实现了冶金结合，无生物毒性，耐磨性能提升了7~10倍。.项目实施共申请国家发明专利5件，其中已获发明授权3件；发表论文13篇，其中SCI收录11篇；培养博士研究生1名，硕士研究生5名。本项目的实施解决了耐磨生物陶瓷涂层制备的关键技术问题，掌握了整套设备的设计与制造技术，为发展我国自主知识产权的高性能耐磨生物陶瓷涂层制造提供了理论基础。