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

这项工程研究启动（ERI）资助支持研究产生先进制造技术的新知识，用于生物医学应用，具有显着的经济和技术效益，以及改善患者的预后。钴-铬-钼合金由于其硬度、韧性和生物相容性而被用作人工关节置换的承载表面。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的严重问题。搅拌摩擦加工是一种先进的制造技术，它利用旋转工具的摩擦力改变金属表面，从而获得轴承表面所需的机械和腐蚀性能。对搅拌摩擦加工先进制造技术的了解的提高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。延长人工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，并且可能是持续使用寿命的植入物与更换失败植入物的复杂翻修手术之间的差异。这项研究是多学科的，并提供教育和推广机会，鼓励代表性不足的群体更多地参与工程研究。搅拌摩擦加工通过极端变形和精确控制材料的热历史来控制微观结构，可以提高材料的耐磨性和耐腐蚀性。本研究阐明了如何控制钴-铬-钼合金的微观结构，如晶粒尺寸，碳化物沉淀和相变，以及它们如何影响耐磨性和耐腐蚀性。极端变形引起动态再结晶和马氏体相变，导致具有高硬度和耐磨性的细晶粒。机械搅拌和控制温度可产生微米级均匀分布的碳化物，这些碳化物可增强钝化氧化物表面层，从而增强耐腐蚀性。研究团队使用多晶立方氮化硼/钨基合金刀具对钴基生物材料进行摩擦搅拌加工实验，并确定了最佳加工条件，如旋转速度，横移速度和施加载荷。销-盘磨损试验和动电位极化/电化学阻抗谱腐蚀试验使用不同的载荷、滑动速度和生物润滑剂对不同处理表面的耐磨性和耐腐蚀性进行量化，选择这些载荷、滑动速度和生物润滑剂来模拟体内人工髋关节植入物。数值模拟捕捉了钴基生物材料的摩擦搅拌加工过程中所获得的基础科学知识和物理机制，并使由这种重要的生物医学合金制成的医疗器械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.