Drilling response of additively manufactured and cast AISI H13 hot-work tool steel by thermal and mechanical processes

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 SLM-H13 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.