Qualification of new steel-alloying strategies for LAM powders by combined in-situ additivation, agglomeration and in-/post-process treatments

SPP 2122中的这一联合提案的主要目标是开发新的起始材料，并通过SLM对其进行加工马氏体可硬化工具钢或铸铁的鉴定。在我们的方法的第一步，我们将考虑我们的战略灰铸铁合金和调整合金化的概念，基于这一知识，以处理白色铸铁（第二步）和莱氏体冷作工具钢（第三步），这两类材料是不可处理的SLM到目前为止。因此，灰铸铁将不通过使用预合金化气体雾化粉末来加工。在这里，我们将混合不同体积分数的SiC颗粒廉价的低合金钢粉末和粉末混合物将通过SLM致密化。目的是实现颗粒的部分熔融，从而形成没有高缺陷密度的“绿色体”。通过SLM（过程中）或热处理（后处理）进一步进行所需的后处理，可以对微观结构和相关材料性能进行特定调整。因此，将研究在SLM处理和后处理（热等静压、超固相线液相烧结）期间散装粉末的混合亚稳组分的溶解，以及必须如何对粉末进行改性以实现完全溶解和不同量的Fe3C或石墨。在第二步和第三步中，我们将进一步添加铁合金粉末，以增加某些元素如Cr，Mn，Ni的含量，从而生产出白色铸铁和莱氏体冷作工具钢。最后，铁合金粉末和纯元素的混合物将以类似的方式进行处理，所述混合物通过附聚来调节以形成可流动的粉末。尽管加工路线不同，但可以分别获得具有相似性能的相似合金或化学成分。如果这一假设能够得到证实，那么只需要几种具有不同化学成分的基本粉末就可以生成多种合金。这可以显著加速用于基于激光的增材制造的新合金的开发，这是由于经济和加工优势，因为微观结构形成过程和内部缺陷的相关形成与SLM致密化过程分离。为了在SPP 2122中处理复杂的材料导向研究，所有方面都将以整体方法解决，包括粉末生产和粉末调节（IWT），合金设计和所设计粉末的SLM加工（LWT）以及SLM组件（WPT）的微观结构，微观磁性和机械特性。

Main objective of this joint proposal within SPP 2122 is the development of new starting materials and their qualification for processing martensitic-hardenable tool steels or cast irons by SLM. In a first step of our approach, we will consider our strategies on grey cast iron alloy and adjust the alloying concepts, based on this knowledge, to process white cast iron (2nd step) and ledeburitic cold work tool steel (3rd step), the two classes of materials that are not processible by SLM till now. Thereby, the grey cast iron will not be processed by using a pre-alloyed gas-atomized powder. Here we will admix different volume fraction of SiC-particles to cheap low-alloyed steel powder and the powder mixture will be densified by SLM. The aim is to realize a partial melting of particles, thus a “green body” is shaped without high defect density. The specific adjustment of the microstructure and the associated materials properties will be obtained by a further required post-processing via SLM (in-process) or heat treatment (post-process). Thereby, dissolution of admixed metastable components of the bulk powder during SLM-processing and post-processing (hot isostatic pressing, super-solidus-liquid phase-sintering) will be investigated and how the powders have to be modified to realize a full dissolution and different amounts of Fe3C or graphite. In the second and third step, we are adding further ferro-alloy powders to increase the content of certain elements like Cr, Mn, Ni in order to produce white cast iron and ledeburitic cold work tool steels. Finally, the mixtures of ferro-alloy powders and pure elements, which are conditioned by agglomeration to form flowable powders, will be processed in a similar way. It is assumed that similar alloys or chemical compositions, respectively, with similar properties can be achieved in spite of the difference in the processing routes. If this hypothesis can be confirmed, only a few basic powders with different chemical compositions are necessary to generate multiple alloys. This can significantly accelerate the development of new alloys for laser-based additive manufacturing due to economic and processing advantages as microstructure formation process and the related formation of internal defects are decoupled from SLM densification process. In order to process the complex material-oriented research within SPP 2122, all aspects will be addressed in a holistic approach with regard to powder production and powder conditioning (IWT), alloy design and SLM-processing of the designed powders (LWT) as well as microstructural, micro-magnetic and mechanical characterization of the SLM-components (WPT).