Laser Directed Energy Deposition Repair of Laser Powder Bed Fusion Maraging Steel Components

Abstract

High-pressure die casting (HPDC) tooling inserts produced via laser powder bed fusion (LPBF) improve thermal balance and extend tool life, but severe thermomechanical cycling inevitably causes surface degradation. While conventional welding repairs introduce excessive heat, laser directed energy deposition (LDED) offers near-net-shape restoration with superior thermal control. However, the mechanical integrity of the LDED deposit-substrate interface remains a critical concern. This thesis investigates strategies to optimize metallurgical bonding at the repair interface of LPBF-produced HPDC inserts. Simulated repair coupons with varying sidewall inclination angles were evaluated using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) to assess defect removal geometries and toolpath parameters. In addition, peak-aged LPBF substrates repaired via LDED were tested for tensile performance and microhardness response to post-repair heat treatment. Results demonstrate that groove sidewall inclination angles of 45–50° produce acceptable bonding under baseline parameters. Steeper angles require contour pass assistance, with power-based energy modification assessed to be effective in promoting sidewall fusion and suppressing geometric deformation. Tensile testing of as-repaired coupons showed intermediate performance (ultimate tensile strength (UTS) = 1482.5 MPa) with consistent interfacial failure. Post-repair peak aging caused interfacial degradation (UTS = 679.80 MPa), attributed to wire electrical discharge machining (EDM) recast layer contamination and Ti-Al oxide inclusions at the interface; heat treatment successfully restored deposit hardness to 53.8 HRC. Ultimately, this work demonstrates that optimizing groove geometry and contour pass energy is vital for LDED repair efficacy, and it highlights that rigorous substrate surface preparation is a prerequisite to achieving mechanically sound repairs in the peak-aged condition.