Effect of chip-induced powder size distribution on 18Ni maraging steel in hybrid additive manufacturing

• Chips change powder size distribution in hybrid additive manufacturing. • Spatter behavior depends on chip characteristics and laser scan speed. • Powder size distribution, oxygen, and splash dynamics promote spatter generation. • Optimized machining parameters reduce chip-related defects. This study investigates the influence of machining-induced chips generated during the milling process on powder characteristics and part quality in hybrid additive manufacturing. The incorporation of chips into the powder bed increased the average particle size and altered particle morphology, reducing both specific surface area and tap density. These changes affected the quality of deposited layers, impacting surface roughness and internal porosity. Irregularly shaped chips acted as defect initiators, contributing to pore formation and mechanical degradation. Compared to conventional additive manufacturing, HAM specimens exhibited more pronounced mechanical deterioration at low and high scan speeds. At low scan speeds, oxygen enrichment caused by chips enhanced the Marangoni effect, increasing spatter formation and pore density. At high scan speeds, irregular powder bed surfaces promoted the ejection of solid spatter, resulting in larger pores. Optimizing machining parameters, such as feed rate and Z pitch, mitigates chip effects, increasing part density and reducing surface roughness while preserving hybrid additive manufacturing advantages. This study clarifies the mechanisms by which chips influence surface and internal defects, providing a foundation for future process optimization to improve the quality and reliability of HAM.