Influence of the combination of stainless steel 316L and nickel alloy IN625 powders during single-layer deposition by laser-directed energy deposition (LP-DED) on corrosion resistance

Components exposed to aggressive environments are typically manufactured using corrosion-resistant alloys (CRAs). The main drawback of these materials is their high cost. Laser-based additive manufacturing technologies offer an opportunity to generate surfaces with high dimensional accuracy and excellent corrosion resistance. In corrosive applications, producing a CRA coating on a lower-cost substrate is highly attractive from a cost-competitiveness perspective.

In a previous study, the feasibility of using LP-DED technology to tailor the pitting resistance equivalent number (PREN) was demonstrated by depositing a single layer using a 50% 316L and 50% IN625 powder mixture. With the aim of further optimizing powder composition without compromising mechanical performance under dynamic loading, and to achieve a more cost-effective solution with adequate corrosion resistance, the present work focuses on 25% 316L–75% IN625 and 75% 316L–25% IN625 powder blends.

Starting from 100% 316L and 100% IN625 CRA powders, coatings were produced via LP-DED on a 42CrMo substrate and characterized using optical and scanning electron microscopy (SEM), small punch testing (SPT), and electrochemical polarization tests in 3.5% NaCl solution.

Increasing the IN625 content refines the dendritic morphology and promotes Nb-Mo enriched Laves phases between dendrites, stabilizing the austenitic matrix and improving tensile strength up to approximately 644 MPa for 100% IN625. Pitting potential also increases from approximately 683 mV (100% 316L) to about 891 mV (100% IN625).

However, intermediate nickel additions showed reduced performance due to suboptimal phase distribution and limited precipitation strengthening, indicating that the beneficial effect of nickel on corrosion resistance and mechanical behavior is maximized only above a critical IN625 fraction.

Among the investigated compositions, the 50 wt.% 316L – 50 wt.% IN625 mixture proved to be the most cost-effective solution, offering significantly improved pitting corrosion resistance while maintaining acceptable mechanical performance for single-layer corrosion protection applications.