Purpose

Depending on an experimental approach to find optimal parameters for producing fully dense (relative density > 99%) Inconel 718 (IN718) components in the selective laser melting (SLM) process is expensive and offers no guarantee of success. Accordingly, this study aims to propose a multi-scale simulation framework to guide the choice of processing parameters in a more pragmatic manner.

Design/methodology/approach

In the proposed approach, a powder layer, ray tracing and heat transfer simulation models are used to calculate the melt pool dimensions and evaporation volume corresponding to a small number of laser power and scanning speed conditions within the input design space. A layer-heating model is then used to determine the inter-layer idle time required to maximize the temperature convergence rate of the solidified layer beneath the power bed. The simulation results are used to train surrogate models to construct SLM process maps for 3,600 pairs of the laser power and scanning speed within the input design space given three different values of the underlying solidified layer temperature (i.e., 353 K, 673 K and 873 K). The ideal selection of laser power and scanning speed of each process map is chosen based on four quality-related criteria listed as follows: without the appearance of key-hole melting; an evaporation volume less than the volume of the d90 powder particles; ensuring the stability of single scan tracks; and avoiding a weak contact between the melt pool and substrate. Finally, the optimal laser power and scanning speed parameters for the SLM process are determined by superimposing the optimal regions of the individual process maps.

Findings

The feasibility of the proposed approach is demonstrated by fabricating IN718 test specimens using the optimal processing conditions identified by the simulation framework. It is shown that the maximum density of the fabricated parts is 99.94%, while the average density is 99.88% and the standard deviation is less than 0.05%.

Originality/value

The present study proposed a multi-scale simulation model which can efficiently predict the optimal processing conditions for producing fully dense components in the SLM process. If the geometry of the three-dimensional printed part is changed or the machine and powder material is altered, users can use the proposed method for predicting the processing conditions that can produce the high-density part.

中文翻译：

---

用于确定使用选择性激光熔化制造高密度 Inconel 718 零件的最佳参数的多尺度模拟方法

目的

依靠实验方法来寻找在选择性激光熔化 (SLM) 工艺中生产完全致密（相对密度 > 99%）Inconel 718 (IN718) 部件的最佳参数是昂贵的，并且不能保证成功。因此，本研究旨在提出一个多尺度模拟框架，以更务实的方式指导加工参数的选择。

设计/方法/方法

在所提出的方法中，粉末层、射线追踪和传热模拟模型用于计算与输入设计空间内的少量激光功率和扫描速度条件相对应的熔池尺寸和蒸发量。然后使用层加热模型来确定使动力床下方凝固层的温度收敛速度最大化所需的层间空闲时间。模拟结果用于训练替代模型，以在给定三个不同的底层凝固层温度值（即 353 K、673 K 和 873 K）的情况下，为输入设计空间内的 3,600 对激光功率和扫描速度构建 SLM 工艺图）。每个工艺图的激光功率和扫描速度的理想选择是基于以下四个与质量相关的标准来选择的： 没有出现小孔熔化；蒸发量小于d90粉末颗粒的体积；保证单扫描轨迹的稳定性；并避免熔池和基材之间的弱接触。最后，通过叠加各个工艺图的最佳区域来确定 SLM 工艺的最佳激光功率和扫描速度参数。

发现

通过使用模拟框架确定的最佳加工条件制造 IN718 试样，证明了所提出方法的可行性。结果表明，制成的零件最大密度为99.94%，平均密度为99.88%，标准偏差小于0.05%。

原创性/价值

本研究提出了一种多尺度模拟模型，该模型可以有效地预测在 SLM 过程中生产完全致密部件的最佳加工条件。如果改变三维打印零件的几何形状或改变机器和粉末材料，用户可以使用建议的方法来预测可以生产高密度零件的加工条件。