Diode area melting of SS316L using low power 450 nm lasers

This study investigates the use of Diode Area Melting (DAM) to process 316L stainless steel (SS316L), an alternative to Laser Powder Bed Fusion (LPBF), utilising independently addressable, low-power (~ 3.5 W) 450 nm blue lasers to address key limitations of LPBF, including thermal control, scalability, and efficiency. A normalised energy density (NED) processing map was developed to ensure successful material melting. Results demonstrated that DAM can achieve a relative density of 99.99% in single-layer SS316L samples using multiple 450 nm blue diode lasers. Notably, DAM-processed SS316L exhibited a significantly higher delta-ferrite content than samples produced via traditional LPBF, which is attributed to the slower cooling rate in DAM (600 °C/s vs. 107 °C/s). This increased delta-ferrite content enhances resistance to stress corrosion cracking in austenitic steel welds. Moreover, sub-grain cellular structures in the DAM-processed SS316L showed a 100% increase in size (4 μm) compared to those produced by LPBF.