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

SPP 2122中的这项联合提案的主要目标是开发新的起始材料及其通过SLM加工马氏体淬火工具钢或铸铁的资格。在我们方法的第一步，我们将考虑我们对灰口铸铁合金的策略，并在此基础上调整合金化概念，以处理白口铸铁(第二步)和莱氏体冷作工具钢(第三步)，这两类材料到目前为止还不能用SLM加工。因此，灰口铸铁将不会使用预合金气雾化粉末进行加工。在廉价的低合金钢粉末中掺入不同体积分数的碳化硅颗粒，对粉末进行SLM致密化。其目的是实现颗粒的部分熔化，从而在不增加缺陷密度的情况下形成“绿体”。微观结构和相关材料性能的具体调整将通过SLM(过程中)或热处理(后处理)进行进一步所需的后处理来获得。因此，将研究在SLM处理和后处理(热等静压、超固相-液相烧结)过程中混合亚稳态成分的块体粉末的溶解，以及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，我们正在进一步添加铁合金粉末，以增加某些元素如铬、锰、镍的含量，以生产白口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，这些粉末经过团聚处理后形成可流动的粉末。假定尽管加工路线不同，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，只需要几个不同化学成分的基本粉末就可以产生多种合金。由于显微组织形成过程和相关内部缺陷的形成过程与SLM致密化过程脱钩，这将大大加快用于激光附加制造的新型合金的开发，因为它具有经济和工艺优势。为了进行SPP 2122中面向复杂材料的研究，将从粉末生产和粉末调质(IWT)、合金设计和所设计粉末(LWT)的SLM加工以及SLM组件(WPT)的微观结构、微磁和机械表征等各个方面进行整体研究。

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).