Fatigue strength of by selective laser melting generated samples

与传统制造工艺相比，增材制造工艺有望节省时间和成本，特别是对于小批量生产的部件。在选择性激光熔化过程中，以粉末形式对单组分金属和合金进行分层加工。该工艺属于完全熔化的增材制造工艺，其中粉末完全重熔，从而在各个层之间形成熔化的冶金键。SLM制造的组件质量的一个明显标准是它与基材相比的密度。需要一种没有孔和裂纹的部件。此外，力学性能也令人感兴趣。目前对其力学性能的系统研究较少，特别是对循环加载下的力学性能的研究较少。过程中的大量影响变量及其相互作用使过程窗口的先验估计和样品的最终性质变得复杂。在第一个资助阶段对钢1.4404和1.2344进行的调查表明，在表面质量改善后，slm生成的材料的失效原因不能减少到现有的残余孔隙率。试样本身在钢基体中也发生了破坏。因此，高疲劳强度不能仅仅与避免残余孔隙率相结合。该项目的目标是实现最高疲劳强度的slm生成部件的均匀力学性能。通过可靠地检测瞬态温度场和熔池特征，可以量化过程中参数变化的影响和反应，并作为设计控制概念的基础。在一个恒定的温度历史，均匀的样品性能与最大的疲劳强度是实现。同时，为了消除奥氏体钢1.4404和工具钢1.2344的残余应力，应对所制造的零件进行不同的热处理。此外，为了进一步提高1.2344工具钢的疲劳强度，还需要开发一种适应试样初始状态的硬化新工艺，使其组织趋于均匀。此外，slm制造的试样在热处理前后的疲劳强度将使用不同的建模方法进行建模，以便能够预测疲劳强度。

Additive manufacturing processes promise to be time and cost saving compared to conventional manufacturing processes, especially for components manufactured in small batches. During the Selective Laser Melting process, one-component metals and alloys in powder form are processed in layers. The process belongs to the class of completely melting additive manufacturing processes in which the powder is completely remelted, whereby a melting metallurgical bond is formed between the individual layers. An obvious criterion for the quality of a component manufactured by SLM is its density in comparison to the base material. A component which is free of pores and cracks is desired. Furthermore, the mechanical properties are of interest. There are only a few systematic investigations, especially for the mechanical properties at cyclic loading. The large number of influencing variables in the process and their interaction with each other complicate a priori estimation with regard to the process window and the resulting properties of the samples.The investigations carried out during the first funding phase on steels 1.4404 and 1.2344 have shown that the causes of failure of SLM-generated materials cannot be reduced to the existing residual porosity after an improvement of the surface quality. The specimens failed in the steel matrix itself as well. Thus high fatigue strength cannot be coupled exclusively to the avoidance of residual porosity. The aim of the project is to realize homogeneous mechanical properties of SLM-generated components of highest fatigue strength. By reliably detecting transient temperature fields and the melt pool characteristics, the influences and the reaction of parameter shifts in the process are to be quantified and used as a basis for the design of a control concept. Over a constant temperature history, homogeneous sample properties with maximized fatigue strength are to be achieved. Simultaneously, different heat treatments of the manufactured parts are to be carried out in order to remove undesirable residual stresses for austenitic steel 1.4404 and tool steel 1.2344. In addition, a new hardening process adapted to the initial state of the specimens is to be developed for tool steel 1.2344 to achieve a homogeneous microstructure in order to further improve its fatigue strength. Furthermore, the fatigue strength of SLM-manufactured specimens before and after heat treatment is to be modelled using different modelling approaches in order to enable the prediction of fatigue strength.