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

这项工程研究启动(ERI)拨款支持为生物医学应用产生先进制造技术的新知识的研究，具有显著的经济和技术效益，以及改善患者的结果。钴铬钼合金因其硬度、韧性和生物相容性而被用作人工关节置换的支撑面。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。搅拌摩擦加工是一种先进的制造技术，它使用旋转工具的摩擦来改变金属表面，从而产生轴承表面非常需要的机械和腐蚀性能。提高对搅拌摩擦加工先进制造技术的了解，使美国经济和医疗器械制造业受益。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巨大影响，这可能是一个持续一生的植入物与复杂的修复手术以取代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，鼓励代表不足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控制微观结构和精确控制材料的热历史来提高材料的耐磨性和耐腐蚀性。这项研究阐明了如何控制钴铬钼合金的微观组织，如晶粒度、碳化物析出和相变，以及它们如何影响耐磨性和耐腐蚀性。极端变形导致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组织。机械搅拌和控制温度可产生微米级均匀分布的碳化物，这些碳化物强化被动氧化物表面层，以增强耐腐蚀性。研究小组使用多晶立方氮化硼/钨-Re合金刀具对钴基生物材料进行了摩擦搅拌加工实验，并确定了最佳加工条件，如转速、横移速度和施加载荷。销盘磨损测试和动电位极化/电化学阻抗谱腐蚀测试量化了使用不同载荷、滑动速度和生物润滑剂模拟体内假体髋关节植入物的不同加工表面的磨损和耐腐蚀性。数值模拟获取了在钴基生物材料的摩擦搅拌加工过程中所获得的基础科学和物理机制方面的知识，并使这种重要的生物医学合金制造的医疗设备的加工计划成为可能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.