What question did this study set out to answer?

The central aim is to evaluate the effectiveness of laser direct energy deposition for repairing maraging steel tooling originally made by laser powder bed fusion.

April 1, 2026Open Access

Microstructural Heterogeneity and Strength Mismatch in Laser Powder Bed Fusion Maraging Steel Tooling Repaired by Laser Direct Energy Deposition

Key Points

The central aim is to evaluate the effectiveness of laser direct energy deposition for repairing maraging steel tooling originally made by laser powder bed fusion.
Examined the feasibility of laser direct energy deposition (LDED) for repairs
Conducted multiscale microstructural characterization
Performed hardness mapping and strength analysis
Identified defects such as porosity and inclusions in the LDED repair material
Restoration of geometrical dimensions achieved with LDED
Notable differences in microstructure between repaired and original materials observed
Yield strength showed strong agreement for original material, but 7.3% deviation in repaired material due to defects
Repaired material mainly consisted of martensite with less austenite and coarser structures

Abstract

This study demonstrates the feasibility of laser-directed energy deposition (LDED) for repairing a service-aged maraging steel high-pressure die-casting insert originally fabricated by laser powder bed fusion (LPBF). Repair of the complex geometry involved defect removal, reverse-engineered groove modelling, and optimization of LDED parameters. Dimensional restoration was achieved; however, internal defects including lack-of-fusion gaps, spherical pores, and Ti-Al-O inclusions formed due to spatter entrapment and melt pool instability. Multiscale microstructural characterization revealed pronounced differences between the repaired region and the original LPBF material despite identical nominal chemistry. The LDED repair material (LRM) consisted primarily of martensite (98.8%) with limited austenite, coarser laths, and reduced precipitate density, whereas the original LPBF material (OPM) contained higher austenite content, refined laths, and a denser precipitate population. These differences arise from the distinct thermal histories associated with LDED solidification and LPBF fabrication followed by aging. Hardness mapping and physically based strengthening analysis were used to relate microstructural features to local mechanical response. Theoretical and experimental yield strengths showed strong agreement for the OPM, while a 7.3% deviation in the LRM was attributed to distributed defects. Direct comparison of the LRM, heat-affected zone, and OPM establishes a microstructure–property map for AM repair of hierarchical maraging steel and highlights how repair-induced thermal cycles generate localized strength gradients in nominally identical alloys. • Demonstrates L-DED repair of a service-aged LPBF maraging steel tool • Links LPBF, HAZ, and L-DED processing to distinct local strength gradients • Highlights challenges of AM repair in complex, groove-confined geometries • Quantifies phase, martensite lath, and precipitate evolution in repair vs base • Identifies Ti–Al–O inclusions and porosity as potential ductility-limiting defects

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