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

基于激光的金属粉末床熔化添加制造技术(PBF-LB/M)经常面临生产提前期较高的问题。为了实现更有效的工艺控制，商业材料将针对PBF-LB/M量身定做。通常，曝光方面的工艺速度由激光功率、轨道距离曝光速度和涂层厚度的比率来描述。一方面影响粉末的吸湿性、润湿性和导热性，另一方面改善粉末的流动性，加速粉末的应用。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，以了解商业上可获得的起始材料的表面功能化的效果及其对颗粒间和激光-材料相互作用的影响。为了进一步深化从SPP2122第一个资助期开始的研究活动，将继续考虑对金属粉末(不锈钢1.4404和工具钢1.2709)进行调查。根据所获得的结果、前期工作和文献综述，以下纳米颗粒添加剂用于表面裁剪：碳化硅和石墨烯(已确定其提高了生产效率和机械性能)、硅(Si)(用于增加熔体的润湿性和平滑熔体表面)和氮化硅(用于提高拉伸性能)。此外，两种原料粉料的颗粒表面都经过了机械和化学处理，以增加比表面积和颗粒粗糙度，从而改善流动性和吸附行为。商业上可用的微米粒度范围的添加剂材料在搅拌的中磨机中进行粉碎，粉碎介质降至较低的纳米范围，并通过湿法沸腾床工艺进行应用。此外，还使用干法强化混合工艺将现有的纳米颗粒沉积到金属颗粒上。将根据所得涂层的团聚程度和均匀度以及所产生的加工性能来比较涂层方法。除了材料组合外，还系统地考虑了添加剂的颗粒大小和加入量。建立的测量系统用于表征吸收、润湿性、流动性以及现场应用，以生成粉末床的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图。对功能化粉末制备的样品进行了微观结构和力学性能的表征。将获得的数据转移到粉末应用的两个模拟模型中，以及不同材料组合的熔池动力学代表了合理的添加。

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.