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Abstract
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Precise micro-hole fabrication in additively manufactured parts has remained a big challenge in such high-accuracy applications
as aerospace, medical devices, and microelectronics. Micro-drilling is one of the critical post-machining techniques
that can overcome such limitations. In view of their different microstructural and mechanical properties, this paper investigates
the micro-drilling performance of AISI H13 tool steel fabricated by selective laser melting (SLM) and casting. The
comparison was performed based on drilling 3 mm micro-holes by mechanical and thermal drilling. The performance of
cast H13 steel with its homogeneous crystalline structure, lower hardness, and residual stress was better than that of SLMH13
both in conventional and laser drilling. It has presented less deformation and higher surface quality with less cutting
waste. In contrast, heterogeneous microstructural SLM-H13 steel showed higher dislocation density due to non-uniform heat
distribution, more molten material, and higher defect incidences after laser drilling. In orbital drilling with WC tools, the
harder SLM-H13 steel also offered high accuracy, while conventional drilling was sufficient in the cast H13. Laser drilling
presented larger kerf angles and heat-affected zones, while the mechanical drilling presented superior dimensional accuracy.
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