Influence of compounding stainless steel 316 L with nickel alloy IN625 powders during laser powder-directed energy deposition for single layer corrosion protection of low-alloy steel

This study analyzes single-layer Laser Powder-Directed Energy Deposition (LP-DED) coatings produced on SAE 4140 low-alloy steel using a Trumpf TruDisk 5001 continuous-wave fiber laser, focusing on the effect of compounding stainless steel 316 L with nickel-based IN625 powder over a wide compositional range on microstructure, mechanical behavior, and corrosion resistance.

Coatings were fabricated with fixed process parameters (1200 W laser power, 2 mm spot diameter, 600 mm·min⁻¹ scanning speed, and 6.5 g·min⁻¹ powder feed rate), and characterized by optical/SEM microscopy, XRD, small punch testing, and electrochemical methods in 3.5 wt% NaCl. 

Increasing IN625 content refined the dendritic morphology, promoted Nb–Mo enriched interdendritic Laves-type phases, and stabilized the austenitic matrix, which together enhanced ultimate tensile strength up to about 644 MPa for 100% IN625 and raised pitting potential from roughly 683 mV (100% 316 L) to about 891 mV (100% IN625). However, low nickel additions (intermediate mixtures) showed reduced strength due to suboptimal phase distribution and limited precipitation hardening, indicating that nickel’s beneficial role in corrosion and strength is maximized only above a critical IN625 fraction.

Among the tested mixtures, 50 wt% 316 L – 50 wt% IN625 emerged as a cost-effective compromise, providing significantly improved pitting corrosion resistance while maintaining acceptable mechanical performance for single-layer corrosion-protection applications.

Acknowledgements: This work was partially funded by the Basque Government under grant number 004-B2/2021, corresponding to the BIKAINTEK Program for PhD students