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

亚琛工业大学数字增材生产DAP主席正在研究一种结构金属表面的新工艺。这种结构不是基于材料的烧蚀，而是基于材料的再分布。再分布是通过调制激光功率的激光重熔来实现的。这种创新工艺的特点和优点是：-制造特别是具有小粗糙度的周期性结构，微米至毫米波长和高度为2至500微米-不烧蚀材料的结构-通过构造反向结构（“破坏性干涉”）从其他制造过程中去除波浪或结构的可能性-在一个加工步骤中构造和激光抛光-化学成分均匀化并在表层产生细颗粒结构，从而增强表面性能。例如，关于耐腐蚀性或硬度可能的应用是增材制造（印刷零件的后处理），机械工程（铣削精密零件的后处理），工具制造（设计表面，可重写金属零件），航空（流体力学）和珠宝（设计表面）。然而，由于该过程的新颖性，仍有许多基本的科学问题有待回答：-完全理解结构形成的潜在机制。钢合金1.2379的矛盾相反行为表明工艺原理尚未完全理解-“反问题”：到目前为止，主要是对激光功率的调制方式进行改变，并对所得到的结构进行研究。需要什么样的调制才能达到理想的表面结构，目前只对周期性结构进行了很少的研究——到目前为止，通过“破坏性干涉”去除结构和波浪形只对一维正弦结构进行了研究。二维窦状结构和非周期结构的去除尚未研究-将结果转移到进一步的金属材料上，并研究材料热物理特性对结构形成的影响-通过重熔建立结构模型，以研究熔体和凝固速率的影响。从固体到液体的体积变化和产生的结构的表面张力-关于小结构（波长< 100 μ m）和面积率的工艺限制的扩展。物理原理在什么程度上限制了构造过程？熔池是否太小或激光调制速度太快而无法形成结构？-通过激光重熔对简单三维几何形状的三维表面（入射角，子区域之间的边界）进行结构研究这些科学问题将在亚琛工业大学DAP主席和莫斯科国家航空技术研究所（NIAT）密切合作的应用项目中进行研究。

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.