Low-Power Direct Energy Deposition of 316L Stainless Steel: Process Parameters, Volumetric Characterization, and Predictive ModelingMANIFEST.TXT

<b>Purpose</b>: Laser-directed energy deposition is an emerging additive manufacturing technique renowned for fabricating or repairing intricate geometric components. This study elucidates the criticality of input processing parameters for minimizing defects/porosity in the deposited weld bead, obtaining desired geometry with regulated contact angles and reaching or surpassing the microhardness of a forged 316L sample.<b>Design/methodology/approach</b>: An experimental investigation applying the Taguchi design explored process parameters, including laser power, traversing speed, and powder feed rate. Over 200 samples were prepared using a hybrid machine with a custom feeder mechanism, which included the development of a unit converter. Characterization of 316L powder material provided grain size and chemical composition. These inputs were packed into mathematical models whose basis was set by introducing specific energy and mass per unit length.<b>Findings</b>: The insights revealed five optimal setups with distinct laser power levels, traversing speeds, and powder feed rates. Five equations calculate the geometry and hardness of any weld track in the manufacturing approach.<b>Originality/value:</b> Different from prior investigations that concentrated on high-power laser systems with swift work speeds, this study focuses on low-power systems (below 400 watts) with reduced traversing speeds (up to 400 mm/min), four powder-feeding nozzles and a 1 mm laser spot diameter. Mathematical models were developed to predict bead geometry, contact angles, and hardness by integrating mass per unit length (MUL) and specific energy (E) as primary variables. Five optimal configurations were identified and validated through over 200 experiments, achieving microhardness comparable to forged 316L with minimal porosity.

<b>研究目的</b>：激光定向能量沉积（Laser-directed energy deposition）是一种新兴的增材制造技术，以可制造或修复复杂几何构件而广受赞誉。本研究阐明了输入加工参数对于降低沉积焊道中的缺陷与孔隙率、获得具备可控接触角的理想几何形状，以及达到或超越锻造316L试样显微硬度的关键作用。
<b>设计/方法/途径</b>：本研究采用田口设计（Taguchi design）开展实验探究，考察了激光功率、扫描速度与送粉率三项加工参数。研究借助搭载定制送粉机构（含单位转换器开发）的混合设备制备了200余组试样。对316L粉末材料进行表征，获取了其晶粒尺寸与化学成分，将上述各项输入量纳入以比能（specific energy, E）与单位长度质量（mass per unit length, MUL）为核心基准构建的数学模型中。
<b>研究结果</b>：研究揭示了五组最优工艺参数组合，各自具备独特的激光功率、扫描速度与送粉率参数。本研究推导得到五组方程，可用于计算该制造方法下任意焊道的几何形状与硬度。
<b>原创性/价值</b>：与此前聚焦高功率激光系统与快速加工速度的研究不同，本研究聚焦于低功率系统（功率低于400瓦）与较低扫描速度（最高400 mm/min），采用四送粉喷嘴以及1 mm的激光光斑直径。本研究以单位长度质量（MUL）和比能（E）作为核心变量，构建了可预测焊道几何形状、接触角与硬度的数学模型。通过200余组实验验证了五组最优工艺配置，所制备试样的显微硬度可媲美锻造316L材料，且孔隙率极低。