Minimisation corrosive attack in the conus-interface of modular endoprothesis by means of definite surface modification via warm deep rolling

对于组配式内假体的单个组件之间的接口，机械工程自锁莫氏锥形接头已经建立良好，其在生理应用期间承受巨大载荷。材料主要采用具有生物惰性的生物相容性金属植入材料Ti6Al4V。在加载过程中，钛（底座）部件之间发生微小移动，这可能导致微动腐蚀过程（应力腐蚀、微动腐蚀或机械诱导缝隙腐蚀）和早期失效。在项目范围内，将进行温深滚压，通过这种方式，除了工艺引起的加工硬化外，还将实现确定的表面形貌。此外，圆锥体的最表面区域将通过局部感应热处理软化，这直接发生在深轧工艺之前。随后，软化和结构化的锥形表面可以在部件的接合期间塑性变形（接合的自适应）。因此，实现了接头间隙的局部密封以防止腐蚀性接头流体的渗透。此外，局部加工硬化和稳定的压缩残余应力将诱导。通过深滚压处理，将减少以离子释放形式的腐蚀过程、体积磨损和模块化接口处的表面材料侵蚀。此外，与纯机械表面处理相比，连续的局部热处理和机械处理进一步提高了耐腐蚀性。本项目范围内的目标和任务是选择（a）结合机械表面处理参数的锥体形状和（B）局部感应热处理，以便在微动疲劳和微动腐蚀方面实现最佳结果。随后，在项目过程中获得的发现使种植体制造商遇到了尚未解决的微动腐蚀磨损问题。最后，历史上建立的锥形界面可以根据现代种植体系统的应用需求进行调整。最后，该项目旨在最大限度地减少材料和设计导致的植入失败，以减少患者和医疗保健系统的身心压力。

For interfaces between single components of modular endoprotheses the mechanical engineering self-locking morse-taper joint is well established, which is subjected to enormous loadings during physiological application. As material the biocompatible metallic implant material Ti6Al4V with bio inert properties is mainly applied. During the loading micro-movements between the titanium (base) components occur, which might lead to fretting corrosion processes (stress corrosion, fretting corrosion or mechanically induced crevice corrosion) and early failure. Within the scope of the project a warm deep rolling will be carried out by which means beside the process induced work hardening a definite surface topography will be achieved. Additionally, the very surface region of the cone will be softened through a local induction heat treatment, which directly occurs right in advance to the deep rolling process. Subsequently, the softened and structured cone surface can deform plastically during joining of the components (self-accommodation of the joint). As a consequence a local sealing of the joint gap against the penetration of corrosive joint fluid is achieved. Furthermore, local work hardening and stabile compressive residual stresses will be induced. Through the deep rolling treatment corrosion processes in form of ion release, volumetric wear and superficial materials attack at modular interfaces will be reduced. In addition the consecutive local thermal and mechanical treatment further increases the corrosion resistance in contrast to a pure mechanical surface treatment. Objective and task within the scope of the project is to choose (a) the shape of the cone in combination with the parameters for the mechanical surface treatment and (b) the local induction heat treatment such that an optimum result is achieved with regard to fretting fatigue and fretting corrosion. Subsequently, the findings gained in the course of the project allow the implant manufacturer to encounter the still unsolved problem of fretting corrosive wear. Finally, the historically established cone interface can be adjusted to the application needs of modern implant systems. In the end the project aims at the minimization of material and design caused implant failures against the background of reducing the physical and psychological pressure of patients and of the health care system.