Structuring by laser remelting for removing waviness or generation of structures on metallic surfaces

RWTH亚琛大学的数字增材生产DAP主席正在研究一种用于结构化金属表面的新工艺。结构化不是基于材料的烧蚀，而是基于材料的重新分布。通过调制激光功率的激光重熔实现再分布。这种创新工艺的特点和优点是：-特别是制造具有小粗糙度的周期性结构，微米至 mm-波长和高度为2至500 µm-无需材料烧蚀的结构化-通过结构化反向结构可以从其他制造工艺中去除波纹或结构（“相消干涉”）-在一个加工步骤中进行结构化和激光抛光-化学组成的均匀化和在表面层中产生细晶粒结构，从而提高了材料的性能。表面，例如关于耐腐蚀性或硬度可能的应用是增材制造（打印部件的后处理）、机械工程（铣削精密部件的后处理）、工具制造（设计表面、可重写金属部件）、航空（流体力学）和珠宝（设计表面）。然而，由于这个过程的新奇，仍然有许多基本的科学问题需要回答：-完全理解结构形成的潜在机制。钢合金1.2379的一个矛盾相反的行为表明，工艺原理尚未完全理解-“逆问题”：到目前为止，主要是激光功率的调制变化和所得的结构进行了研究。实现所需表面结构所需的调制仅稍微研究并且仅针对周期性结构-到目前为止，仅针对一维正弦结构研究了通过“相消干涉”去除结构和波纹。尚未研究二维正弦和非周期性结构的去除-将结果转移到其他金属材料上并研究热物理材料性质对结构形成的影响-通过重熔进行结构化建模以研究熔化和凝固速率的影响，从固体到液体的体积变化和所得结构上的表面张力-扩展了有关小结构（波长< 100 µm）和面积率的工艺限制。在什么情况下，物理原理限制了结构化过程？熔池是否太小或激光调制是否太快而无法形成结构？在简单的3D几何形状上通过激光重熔3D表面（入射角，子区域之间的边界）进行结构化的研究这些科学问题将在应用项目中进行研究，该项目由RWTH亚琛大学的DAP主席和莫斯科的国立航空技术研究所NIAT密切合作。

The Chair for Digital Additive Production DAP of RWTH Aachen University is investigating a new process for structuring metallic surfaces. The structuring is not based on ablation of material but on redistribution of material. The redistribution is achieved by laser remelting with modulated laser power. Characteristics and advantages of this innovative process are:- Manufacturing especially of periodic structures with small roughness, µm- to mm-wavelengths and heights of 2 to 500 µm- Structuring without ablation of material - Possibility for removing the waviness or structures from other manufacturing processes by structuring the inverse structure (“destructive interference”)- Structuring and laser polishing in one processing step- Homogenization of the chemical composition and generation of a fine grain structure in the surface layer and therefore enhancing the properties of the surface, e.g. regarding corrosion resistance or hardnessPossible applications are additive manufacturing (post processing of printed parts), mechanical engineering (post processing of milled precision parts), tool making (design surfaces, rewriteable metallic parts), aeronautics (fluid mechanics) and jewelry (design surfaces). However, due to the novelty of the process there are still many fundamental scientific questions to be answered:- Complete comprehension of the underlying mechanisms for structure formation. A paradox opposite behavior of steel alloy 1.2379 suggests that the process principle is not yet fully understood- “Inverse Problem”: Up to now mainly the modulation of the laser power was varied and the resulting structures were investigated. Which modulation is required to achieve a desired surface structure is only slightly investigated and only for periodic structures- Up to now the removing of structures and waviness by “Destructive Interference” is only investigated for 1-dimensional sinusoidal structures. The removing of 2-dimensional sinus and also aperiodic structures is not investigated yet- Transfer of the results on further metallic materials and investigation of the influence of the thermo-physical material properties on the structure formation- Modeling of structuring by remelting for investigating the influence of melt and solidification rate, volume change from solid to liquid and surface tension on the resulting structures- Extension of the process limits regarding small structures (wavelength < 100 µm) and area rate. At what point do physical principles limit the structuring process? Can a melt pool be too small or laser modulation too fast for structure formation?- Investigation of structuring by laser remelting for 3D surfaces (angle of incidence, borders between subareas) on simple 3D geometriesThese scientific questions shall be investigated in the applied project in a close collaboration between the chair DAP of RWTH Aachen University and the National Institute of Aviation Technologies NIAT in Moscow.