Grain refinement in the surface layer of metallic materials by means ofmachine hammer peening (FinePeening)

具有细晶粒微观结构的金属材料具有与粗晶粒状态下相同的更好的机械性能。细晶粒金属材料的强度、疲劳强度、耐磨性和耐腐蚀性的增加已经被实验证明。因此，金属材料的晶粒细化是显著提高其力学性能的一种很有前途的方法。由于这一事实，表面层中的局部晶粒细化改善了整个部件的性能。表面层中的晶粒细化可以通过机械表面处理的方式通过剧烈塑性变形（SPD）来实现。机锤喷丸是一种工业上常用的高载荷技术部件的机械表面处理工艺，通过机锤喷丸可以实现表面粗糙度的平滑化、应变硬化以及在表面层中诱导残余压应力。此外，MHP结构，以改善表面的摩擦学特性可以产生。这两个方面都是MHP领域以前研究的重点。此外，MHP是一种潜在的合适的技术，用于产生细粒度的表面层。然而，目前还没有关于MHP的工艺参数和在表面层中产生的晶粒细化的解释模型，为了能够实现MHP用于晶粒细化的目标导向的工业实施，必须解释MHP工艺参数和在表面层中产生的晶粒细化之间的基本因果关系。此外，MHP处理部件的细晶粒表面层对磨损和疲劳强度的影响将被表征。

Metallic materials with a fine-grained microstructure have better mechanical properties as in a coarse-grained state. An increase of strength, fatigue strength, wear, and corrosion resistance of fine grained metallic materials has already been proven experimentally. Therefore, the grain refinement of metallic materials is a promising approach to significantly improve their mechanical properties.The surface layer is often the most loaded zone of technical components. Due to this fact a local grain refinement in the surface layer improves the performance of the complete component. A grain refinement in the surface layer can be achieved through severe plastic deformation (SPD) by means of mechanical surface treatment. Machine hammer peening (MHP) is an industrially used process for mechanical surface treatment of highly loaded technical components.A smoothening oft the surface asperities, strain hardening, and induction of compressive residual stresses in the surface layer are achiever by means of MHP. Furthermore, MHP structures to improve the tribological characteristics of the surfaces can be produced. Both mentioned aspects were in the focus of previous research in the field of MHP. Furthermore, MHP is a potentially suitable technology for a generation of a fine-grained surface layer. However, there exist no explanation models with regard to the process parameters of MHP and the resulting grain refinement in the surface layer.In order to enable a goal-oriented industrial implementation of MHP for the grain refinement, basic cause-and-effect relationships between the MHP process parameters and the resulting grain refinement in the surface layer must be explained. Furthermore, the influence of the fine-grained surface layer of MHP treated components on the wear and fatigue strength is to be characterized.