Additive manufacturing (AM) is known for its rapid heating and cooling cycles, which causes produced parts to have complicated thermal histories. The addition of each layer in this process, introduces a steep thermal gradient, which in turn influences the residual stresses and geometrical accuracy of then final parts. This is further intensified in directed energy deposition (DED), in which the thermal gradients and melt pools tend to be higher and larger respectively. Given that the occurrence of these repetitive heating cycles is inevitable, it is advised to try to minimize the temperature gradient in every cycle. This would have the effect of reducing the residual stresses and consequently help with achieving higher geometrical accuracy in the fabricated component.

Controlling the pause between the deposition of successive layers, known as the interlayer dwell time, presents a straightforward method for managing thermal conditions. Introducing a pause between layers can allow excess heat to dissipate before the addition of the subsequent layer, thereby reducing heat accumulation [1, 2, 3]. On the other hand, a dwell time that is too long can lead to the significant cooling of previously deposited layers, which then creates a high thermal gradient as the next layer is deposited [4, 5]. This parameter is significantly important when manufacturing large components, where the time gap between successive layers can be substantial [6]. Despite its ease of adjustment, interlayer dwell time remains under-investigated, especially for stainless steel 316L. This knowledge gap is highlighted by a study reporting contradictory effects for 10s and 20s dwell times [5].

In this work, multiple thin-wall samples are first deposited under identical conditions and then heat treated to remove residual stresses. These stress-free pre-walls serve as reference bases for Digital Image Correlation (DIC) analysis, enabling a direct comparison of deformation across samples. Each wall is then repositioned, and a post-wall is deposited under different interlayer dwell time settings. By analysing how each post-wall deposition affects deformation of the stress free pre-walls, we aim to find the dwell time value that caused the least amount of distortion in the samples. The aim is to find a dwell time that, on one hand, minimizes thermal accumulation and on the other does not reduce the temperature of the part so much as to introduce a significantly higher thermal gradients than if no dwell time was introduced.

References

[1] S. H. I. Jingjing; Journal of Advanced Manufacturing Science and Technology, 2024, 4, 2024015-2024015.

[2] Y. Zhao; Additive Manufacturing, 2020, 32, 100935.

[3] Y. Su; International Journal of Mechanical Sciences, 2024, 280, 109519.

[4] A. Kumar; Materials Chemistry and Physics, 2025, 340, 130807.

[5] G. Piscopo; Lasers in Manufacturing and Materials Processing, 2024, 11, 419-436.

[6] Z. Wang; Materials & Design, 2017, 113, 169-177.