Development of surface tailored metal powders for increased production efficiency at the laser powder-bed fusion additive manufacturing process

使用基于激光的系统（PBF-LB/M）的金属粉末床熔融的增材制造技术经常面临高生产交付时间的问题。为了实现更有效的过程控制，将为PBF-LB/M定制商业材料。通常，曝光方面的处理速度由激光功率、轨道距离曝光速度和层厚度的比率来描述。一方面影响粉末的吸附性、润湿性和导热性，另一方面改善粉末的流动性以加速粉末的应用是非常感兴趣的。因此，该研究项目的总体目标是开发一种基本的材料和工艺，了解市售起始材料的表面功能化的影响及其对粒子间和激光-材料相互作用的影响。为了进一步深化SPP 2122第一个资助期的研究活动，将继续考虑对金属粉末（不锈钢1.4404和工具钢1.2709）进行研究。基于所获得的结果、初步工作和文献综述，以下纳米颗粒添加剂用于表面修整：碳化硅和石墨烯（已经确定其提高的生产效率和机械性能）、硅（Si）（以增加熔体的润湿性并使熔体表面光滑）和氮化硅（以增加拉伸性能）。此外，对两种原始原料粉末材料的颗粒表面进行机械和化学处理，以增加比表面积、颗粒粗糙度，从而改善流动性和吸收行为。将微米尺寸范围内的市售添加剂材料在搅拌的中间米尔斯磨机中用研磨介质研磨至较低的纳米范围，并通过湿流化床工艺施加。此外，干式强化混合工艺用于将现有的纳米颗粒存款到金属颗粒上。将在所得涂层的团聚程度和均匀性以及所得加工性能方面对涂覆方法进行比较。除了材料组合之外，还系统地考虑了添加剂的粒度和负载。已建立的测量系统用于表征吸收性、润湿性、流动性以及原位应用，用于生成粉末床的µCT图像、粉末应用和熔化行为的高速图像以及粉末床的三维映射。从功能化粉末生产的样品的特征在于相对于微观结构和机械性能。将获得的数据转换为粉末应用和不同材料组合的熔池动力学的两个模拟模型代表了合理的添加。

The additive manufacturing technology powder bed fusion of metals using a laser based system (PBF-LB/M) is often confronted with the issue of high production lead times. To enable a more efficient process control, commercial materials will be tailored for PBF-LB/M. Typically, the process speed in terms of exposure is described by the ratio of laser power, track distance exposure speed and layer thickness. On one hand it is of great interest to influence absorption, wettability and thermal conductivity of the powder, and on the other hand to improve the flowability to accelerate the powder application. Accordingly, the overall goal of the research project is to develop a fundamental material and process understanding of the effects of surface functionalizations of commercially available starting materials and their influence on interparticle and laser-material interactions. To further deepen the research activities from the first funding period of SPP 2122, the metal powders (stainless steel 1.4404 and tool steel 1.2709) will be continuously considered for investigation. Based on the gained results, preliminary work and literature review, the following nanoparticle additives are used for surface tailoring: Silicon carbide and graphene (for which an increased production efficiency and mechanical properties have already been determined), silicon (Si) (to increase the wettability of the melt and to smooth the melt surfaces) and silicon nitride (to increase tensile properties). In addition, the particle surfaces of both original feedstock powder materials are treated mechanically and chemically to increase the specific surface, particle roughness, and hence to improve the flowability and absorption behavior. The commercially available additive materials in the micrometer size range are milled in stirred medial mills with grinding media down to the lower nanometer range and are applied by a wet fluidized bed process. In addition, dry intensive mixing processes are used to deposit existing nanoparticles onto the metal particles. The coating methods will be compared in terms of degree of agglomeration and homogeneity of the resulting coatings as well as resulting processing properties. In addition to the material combinations, particle sizes and loadings of the additives are systematically considered. Established measurement systems are used for the characterization of absorption, wettability, flowability as well as in-situ applications for the generation of µCT images of a powder bed, high-speed images of the powder application and the melting behavior as well as three-dimensional mappings of the powder bed. Samples produced from the functionalized powders are characterized with respect to microstructure and mechanical properties. The transfer of the obtained data into two simulative models of the powder application and the melt pool dynamics of different material combination represent a reasonable addition.