Tool steels and their additive manufacturing for fabrication and repair via PBF and DED processes: techniques, challenges, and applications

This review investigates the state of additive manufacturing (AM) of tool steels with a clear, process-aware scope that centers on two dominant AM routes, direct energy deposition (DED) and powder bed fusion (PBF), and their respective roles in fabrication and repair. First, different categories of tool steels and their common damage mechanisms are introduced. The distinct process mechanisms, material responses, and performance metrics characteristic of each technique is outlined, and then how microstructure, residual stresses, porosity, and carbide chemistry emerge under DED and PBF processes for different type of alloys are explained. By contrasting process-specific challenges, such as larger melt pools and intrinsic tempering in DED versus rapid solidification and fine microstructures in PBF, with end-use requirements, e.g. wear resistance, toughness, and reliability in tooling, we reveal common optimization approaches, preheating strategies, parameter windows, post-processing heat treatments, and robust non-destructive evaluation are delineated in this work. The review also assesses the material compatibility, challenges, and economic and environmental considerations of AM tooling, and highlights gaps where cross-process insights can accelerate industrial adoption and discussed future trends. The aim is to provide a coherent, process-aware framework that connects AM physics, materials science, and engineering performance for tool steels.