ERI: Friction Stir Processing for Durability of Cobalt-Chromium-Molybdenum Biomaterials

这项工程研究启动（ERI）资助支持为生物医学应用产生先进制造技术新知识的研究，具有显著的经济和技术效益，并改善患者的治疗效果。钴铬钼合金因其硬度、韧性和生物相容性而被用作假体关节置换的承载面。然而，假体植入材料在人体内的磨损和腐蚀仍然是许多患者面临的严重问题。摩擦搅拌加工是一种先进的制造技术，它利用旋转工具的摩擦来改变金属表面，从而产生对轴承表面非常理想的机械和腐蚀性能。提高搅拌摩擦加工先进制造技术的知识有利于美国经济和医疗器械制造业。它还使每年接受全关节置换手术的数百万患者受益。延长假体关节植入物的耐用性对这些患者的生活质量有着巨大的影响，并且可能是持续一生的植入物与复杂的修复手术以替换失败的植入物之间的区别。这项研究是多学科的，并提供教育和推广机会，以鼓励未被充分代表的群体更多地参与工程研究。搅拌摩擦加工可以通过极端变形和精确控制材料的热历史来控制微观结构，从而提高材料的耐磨损和耐腐蚀性能。本研究阐明了如何控制钴铬钼合金的微观组织，如晶粒尺寸、碳化物析出和相变，以及它们如何影响磨损和耐腐蚀性。极端变形引起动态再结晶和马氏体相变，产生具有高硬度和耐磨性的细晶粒。机械搅拌和控制温度产生微米大小，均匀分布的碳化物，强化被动氧化物表面层，增强耐腐蚀性。研究团队利用多晶立方氮化硼/钨铼合金刀具对钴基生物材料进行搅拌摩擦加工实验，确定最佳加工条件，如转速、横移速度、外加载荷等。针盘式磨损测试和动电位极化/电化学阻抗谱腐蚀测试量化了不同加工表面的磨损和耐腐蚀性，使用不同的载荷、滑动速度和选择的生物润滑剂来模拟体内人工髋关节植入物。数值模拟捕获了在钴基生物材料的搅拌摩擦加工过程中所获得的基础科学知识和物理机制，并为由这种重要的生物医学合金制成的医疗设备制定了加工计划。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Engineering Research Initiation (ERI) grant supports research generating new knowledge of advanced manufacturing techniques for biomedical applications, with significant economic and technological benefits, as well as improved patient outcomes. Cobalt-chromium-molybdenum alloys are used as the bearing surfaces of prosthetic joint replacements because of their hardness, toughness, and biocompatibility. However, wear and corrosion of prosthetic implant materials in the human body remain serious problems for many patients. Friction stir processing is an advanced manufacturing technique that uses friction from a rotating tool to alter the metal surface, resulting in mechanical and corrosion properties that are highly desirable for bearing surfaces. Improved knowledge of the friction stir processing advanced manufacturing technique benefits the U.S. economy and medical device manufacturing industry. It also benefits millions of patients who undergo total joint replacement surgeries each year. Extending the durability of a prosthetic joint implant has an enormous impact on the quality of life of these patients and could be the difference between an implant that lasts a lifetime and complicated revision surgeries to replace failed implants. This research is multidisciplinary and provides education and outreach opportunities to encourage increased participation of underrepresented groups in engineering research.Friction stir processing can increase the wear and corrosion resistance of materials by controlling the microstructure through extreme deformation and precise control over the thermal history of the material. This research elucidates how the cobalt-chromium-molybdenum alloy microstructure such as grain size, carbide precipitation, and phase transformations can be controlled, and how they affect both wear and corrosion resistance. Extreme deformation causes dynamic recrystallization and martensitic phase transformations, resulting in fine grains with high hardness and wear resistance. Mechanical stirring and controlled temperature cause micron-sized, uniformly distributed carbides that strengthen passive oxide surface layers to bolster corrosion resistance. The research team performs friction stir processing experiments on the cobalt-based biomaterials with a polycrystalline cubic boron nitride/tungsten-rhenium alloy tool, and determines optimum processing conditions such as rotation speed, traverse speed, and applied load. Pin-on-disk wear tests and potentiodynamic polarization/electrochemical impedance spectroscopy corrosion tests quantify the wear and corrosion resistance of the different processed surfaces using different loads, sliding speeds, and biological lubricants selected to mimic an in-vivo prosthetic hip implant. Numerical simulations capture the gained knowledge of the basic science and physical mechanisms in play during friction stir processing of cobalt-based biomaterials and enable processing plans for medical devices made from this important biomedical alloy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.