Abstract To address issues such as melt pool instability and weld formation defects caused by substrate inclination in spatially inclined arc additive manufacturing, this study systematically investigates the effects of welding torch angle and substrate inclination on weld formation and melt pool dynamics using aluminum alloys as the research subject and the wire-arc directed energy deposition (Wire-Arc DED) welding method. A combined approach of “theoretical analysis and experimental verification” was employed. Utilizing high-speed camera recording and electrical signal oscillograph acquisition, the study examined the transition behavior of molten droplets, the flow characteristics of the melt pool, and the patterns of microstructural and mechanical property changes. Results indicate that when the welding torch is perpendicular to the substrate, the arc morphology is symmetrical and stable, material transfer is uniform, and short-circuit frequency decreases. As the substrate inclination angle increases, the melt pool exhibits an accelerated downward flow trend due to the dominant influence of gravity. The deposition width remains within the range of 10–11 mm, with a fluctuation amplitude of 13.6%. The microstructure at the bottom of the specimen exhibited fine columnar grains, while the top showed coarse dendrites. The substrate inclination caused grain refinement on the flow side and coarsening on the accumulation side. Microhardness gradually decreased from the base metal to the weld top, with substrate inclination not altering this evolution pattern. Highlights <OrderedList> <ListItem> <ItemNumber>(1)</ItemNumber> <ItemContent> When the welding torch is perpendicular to the substrate, the arc forms a symmetrical bell shape with uniform and stable droplet transition (2.5 ms neckdown, 1.5 ms flight phase), minimal electrical signal fluctuations, and ideal weld bead formation. </ItemContent> </ListItem> <ListItem> <ItemNumber>(2)</ItemNumber> <ItemContent> Horizontal substrate welding produces symmetrical flow in the molten pool, resulting in a smooth weld surface. Increasing the inclination angle causes unidirectional flow in the molten pool, leading to collapse and reduced uniformity in the deposited layer. </ItemContent> </ListItem> <ListItem> <ItemNumber>(3)</ItemNumber> <ItemContent> As the number of additive layers increases, thermal accumulation leads to grain coarsening. Substrate inclination alters heat conduction pathways, causing grains on the flow side to become finer and denser while grains on the build-up side coarsen. </ItemContent> </ListItem> <ListItem> <ItemNumber>(4)</ItemNumber> <ItemContent> Porosity originates from gas escaping at a slower rate than solidification. On the flow side, influenced by temperature gradients, porosities exhibit larger volumes, greater numbers, and denser distribution. </ItemContent> </ListItem> <ListItem> <ItemNumber>(5)</ItemNumber> <ItemContent> The overall microhardness exhibits a gradual decrease from the base metal to the weld toe. Porosity and interlayer structures may cause localized hardness fluctuations, but the substrate inclination does not alter this overall trend. </ItemContent> </ListItem> </OrderedList>

Effect of substrate inclination angle on weld geometry and melt pool dynamics

期刊论文
发表日期：

2026年2月12日

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Pan Gao,
Jiahao Liang,
Shilong Qu,
Xin Zhao,
Yazhou Jia,
Jingtao Peng,
Yunjing Chen,
Qiang Ling

摘要

Abstract

To address issues such as melt pool instability and weld formation defects caused by substrate inclination in spatially inclined arc additive manufacturing, this study systematically investigates the effects of welding torch angle and substrate inclination on weld formation and melt pool dynamics using aluminum alloys as the research subject and the wire-arc directed energy deposition (Wire-Arc DED) welding method. A combined approach of “theoretical analysis and experimental verification” was employed. Utilizing high-speed camera recording and electrical signal oscillograph acquisition, the study examined the transition behavior of molten droplets, the flow characteristics of the melt pool, and the patterns of microstructural and mechanical property changes. Results indicate that when the welding torch is perpendicular to the substrate, the arc morphology is symmetrical and stable, material transfer is uniform, and short-circuit frequency decreases. As the substrate inclination angle increases, the melt pool exhibits an accelerated downward flow trend due to the dominant influence of gravity. The deposition width remains within the range of 10–11 mm, with a fluctuation amplitude of 13.6%. The microstructure at the bottom of the specimen exhibited fine columnar grains, while the top showed coarse dendrites. The substrate inclination caused grain refinement on the flow side and coarsening on the accumulation side. Microhardness gradually decreased from the base metal to the weld top, with substrate inclination not altering this evolution pattern.

Highlights

(1)

When the welding torch is perpendicular to the substrate, the arc forms a symmetrical bell shape with uniform and stable droplet transition (2.5 ms neckdown, 1.5 ms flight phase), minimal electrical signal fluctuations, and ideal weld bead formation.

(2)

Horizontal substrate welding produces symmetrical flow in the molten pool, resulting in a smooth weld surface. Increasing the inclination angle causes unidirectional flow in the molten pool, leading to collapse and reduced uniformity in the deposited layer.

(3)

As the number of additive layers increases, thermal accumulation leads to grain coarsening. Substrate inclination alters heat conduction pathways, causing grains on the flow side to become finer and denser while grains on the build-up side coarsen.

(4)

Porosity originates from gas escaping at a slower rate than solidification. On the flow side, influenced by temperature gradients, porosities exhibit larger volumes, greater numbers, and denser distribution.

(5)

The overall microhardness exhibits a gradual decrease from the base metal to the weld toe. Porosity and interlayer structures may cause localized hardness fluctuations, but the substrate inclination does not alter this overall trend.