Influence of inclined substrate on process characteristics of directed energy deposition

Directed Energy Deposition (DED) has the potential to be widely used in many industries. Deposition on non-horizontal substrate is a practical process that must be faced, but it is rarely studied. This paper discusses the interaction between laser, powder, and inclined substrate based on an analytical model and the deposition profile measurements. It shows that the inclined angle of substrate has a significant effect on the laser energy density and powder flow mass distributions on the inclined substrate. Also, the influence of gravity and surface tension of liquid melt pool cannot be ignored during the deposition process on the inclined substrate, resulting in the significant difference between the simulated and measured deposited height. With increasing inclined angle of the substrate, the melt pool tends to flow downward due to the effect of gravity and surface tension, forming a concave melt pool in the upward scanning strategy and the horizontal melt pool in the downward scanning strategy, resulting in a greater deposited height in the upward scanning strategy and lower deposited height in the downward scanning strategy relative to the simulated results. Also, more adhered powders were formed on the deposited layer surface in the upward scanning strategy compared to that in the downward scanning strategy due to the lower laser energy distribution on the tail of the upward melt pool.