A Comparative Analysis of LPBF Process Maps for S2 and S6 Grades Tool Steel

Laser Powder Bed Fusion (LPBF) represents a significant advancement in metal additive manufacturing, facilitating the near-net-shape fabrication of intricate, high-performance tool-steel components. This process is accomplished through a layer-by-layer selective melting technique and extremely rapid solidification (ranging from 10³ to 10⁶ K/s). The establishment of process maps — both empirical and predictive frameworks that correlate variables such as laser power, scan speed, and defect thresholds — is crucial for defining processing windows and optimising parameter selection. In tool steels, the influence of alloying elements is significant as they affect solidification behaviour, phase stability, and susceptibility to cracking. Carbide-forming additions can constrict the defect-free range, while stabilising elements can enhance toughness and dimensional accuracy. This study aims to develop a process map for S6 tool steel by varying laser scan speed and laser power. Small cubes are printed using various combinations of these parameters, followed by microstructural characterisation of the as-built material. This characterisation includes optical microscopy (OM) and porosity assessment. After establishing the process map for S6, the resulting microstructures are compared with those previously characterised for LPBF-processed S2 tool steel. This comparison provides valuable insight into the differences in the as-built microstructures of LPBF S2 and LPBF S6, particularly in relation to how the presence and relative amounts of alloying elements influence processability and microstructural development.