引用本文:邵勇,孙树峰,王萍萍,蒙卡·彼得·帕沃尔,陈博文,张丰云,王茜,孙维丽.医用TC4钛合金激光-化学复合抛光及表面形貌演化[J].中国表面工程,2024,37(2):227~237
SHAO Yong,SUN Shufeng,WANG Pingping,MONKA Peter Pavol,CHEN Bowen,ZHANG Fengyun,WANG Xi,SUN Weili.Laser-chemical Composite Polishing and Surface Morphology Evolution of Medical TC4 Titanium Alloy[J].China Surface Engineering,2024,37(2):227~237
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医用TC4钛合金激光-化学复合抛光及表面形貌演化
邵勇1, 孙树峰1, 王萍萍2,3, 蒙卡·彼得·帕沃尔3, 陈博文1, 张丰云1, 王茜1, 孙维丽4
1.青岛理工大学机械与汽车工程学院 青岛 266520;2.青岛理工大学信息与控制工程学院 青岛 266520;3.斯洛伐克科希策技术大学制造技术学院 普雷绍夫 08001;4.青岛黄海学院智能制造学院 青岛 266427
摘要:
表面粗糙度是医疗器械构件最重要的质量特征之一,然而现有的激光抛光、化学抛光等单一表面抛光技术存在一定局限性。针对医用 TC4 钛合金表面的精密抛光需求,设计并搭建一套激光-化学复合抛光系统,通过激光-化学复合加工材料去除机理分析和开展 TC4 钛合金的激光-化学复合抛光试验,深入探究复合抛光过程中不同抛光阶段材料表面形貌的演变过程及粗糙度变化并进行分析,进而明确激光-化学复合抛光机理。研究结果表明,激光-化学复合抛光材料去除是基于激光热-力效应与激光诱导化学腐蚀溶解共同作用的结果,而且两者具有一定协同效应,在适当的工艺窗口内,化学腐蚀溶解可以完全去除激光烧蚀产生的残渣和重熔物。激光辐照会在工件表面“峰-谷”区域产生温度差,进而导致化学溶解速率差异,即“山峰”区域溶解速率快,“山谷”区域溶解速率慢,从而实现表面粗糙度的降低。最后采用合适的工艺参数,优化了抛光效果, 实现了医用 TC4 钛合金的选择性精密抛光,激光辐照区域表面粗糙度 Ra 由初始的 5.230 μm 下降至 0.225 μm, Sa 由初始的 8.630 μm 下降至 0.571 μm,分别下降 95.7%和 93.4%。研究结果可为钛合金或其他自钝化金属的精密抛光提供参考。
关键词:  激光  钛合金  抛光  表面形貌  化学腐蚀
DOI:10.11933/j.issn.1007-9289.20230227001
分类号:TN249
基金项目:国家自然科学基金(51775289);高等学校学科创新引智计划(D21017);中国-斯洛伐克双边政府间交流项目(国科外[2022]5 号-12);青岛西海岸新区科技项目(2021-70);青岛西海岸新区科技项目(源头创新专项)(2020-103)
Laser-chemical Composite Polishing and Surface Morphology Evolution of Medical TC4 Titanium Alloy
SHAO Yong1, SUN Shufeng1, WANG Pingping2,3, MONKA Peter Pavol3, CHEN Bowen1, ZHANG Fengyun1, WANG Xi1, SUN Weili4
1.College of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao 266520 , China;2.College of Information and Control Engineering, Qingdao University of Technology, Qingdao 266520 , China;3.Faculty of Manufacturing Technologies, Technical University of Ko?ice, Slovakia, Presov 08001;4.College of Intelligent Manufacturing, Qingdao Huanghai University, Qingdao 266427 , China
Abstract:
Surface finish is a crucial quality characteristic of medical device components. However, existing surface polishing technologies have some shortcomings, such as difficulty in controlling the polishing effect, poor precision, and inability to manage components with complex shapes. In this study, a laser-chemical composite polishing system was designed and built for the precision polishing of medical-grade TC4 titanium alloy. The material removal mechanism of laser-chemical composite machining was analyzed. The evolution process of the material surface morphology and surface roughness changes at different polishing stages was investigated by conducting laser chemical composite polishing experiments on medical TC4 titanium alloys; thus, clarifying the mechanism of laser chemical composite polishing. The results show that material removal by laser-chemical composite polishing is based on the combined influence of laser thermal-mechanical effects and laser-induced chemical corrosion. Moreover, these two factors have a synergistic effect under certain conditions, which can mutually promote and enhance material removal efficiency and processing quality. Within an appropriate process window, chemical dissolution can completely remove the residues and remelts generated by laser ablation. Laser irradiation causes temperature differences between the peak and valley regions of the material surface, leading to different chemical dissolution rates. By exploiting the difference in the dissolution rates between the peaks and valleys on the surface of the workpiece, improvements in the surface roughness of the laser-irradiated region were achieved. Moreover, the chemical polishing mechanism is based on the atomic-scale dissolution of materials, which results in higher polishing precision compared with laser thermo-mechanical etching. The ratio of the laser etching material removal to the chemical dissolution material removal determines the ultimate roughness limit of the titanium alloy surface. A higher proportion of chemical dissolution resulted in better surface smoothness but a lower polishing efficiency. Therefore, during the final polishing stage, reducing the energy of laser irradiation on the workpiece surface can decrease the laser etching ratio and improve the final polishing effect. Additionally, the uneven distribution of the alloying elements on the surface of the TC4 titanium alloy affected the final surface smoothness. This is because Al and Fe in TC4 titanium alloys exhibit better chemical activity in acidic environments than V and Ti. During the chemical corrosion process, micro-galvanic cell phenomena occur, leading to preferential dissolution of the anode. Therefore, based on the chemical polishing mechanism, it can be understood that the ultimate polishing limit is influenced by the purity and microstructure of the material. The purer the material composition and smaller the microstructure, the better the final polishing effect. The selective removal of laser-chemical composite polishing is based on laser etching and thermo dissolution induced by laser activation. During laser-chemical composite polishing, laser irradiation acts as a local and selective heat source, inducing appropriate thermal shock and activating a non-uniform chemical reaction between the chemical solution and metal surface, resulting in temperature-induced chemical corrosion. In the laser irradiation area, the passivation film on the metal surface was stripped and dissolved under the dual action of physics and chemistry, whereas other parts of the workpiece material were protected by the passivation film, and almost no corrosion occurred. Under the continuous action of laser etching and chemical dissolution, the etching rates in the laser-irradiated and non-irradiated areas were significantly different, thereby achieving selective etching of the metallic material. The presence of bubbles during processing significantly affects the laser-chemical composite polishing. The causes of bubble generation were analyzed, and several methods were proposed to overcome bubble disturbances. It was demonstrated through experiments that, after taking appropriate measures, the bubble disturbance during the polishing process can be effectively reduced. Finally, the selective precision polishing of the medical TC4 titanium alloy was achieved using suitable process parameters. The surface roughness of laser irradiation area Ra decreased from 5.230 μm to 0.225 μm, and Sa decreased from 8.630 μm to 0.571 μm, which is a decrease of 95.7% and 93.4%, respectively. These research findings provide a reference for the precision polishing of titanium alloys or other self-passivating metals.
Key words:  laser  titanium alloys  polishing  morphology  chemical etching
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