Mechanism of Enhanced Pitting Corrosion Resistance in L‐DED 17‐4PH Stainless Steel via a 760°C Conditioning Treatment

ABSTRACT

This study elucidates the mechanism by which a 760°C conditioning treatment, inserted between solutionizing and aging (SCA process), reverses the pitting corrosion resistance degradation in laser‐directed energy deposited (

‐DED) 17‐4PH stainless steel, compared with the conventional solutionizing and aging (SA) treatment. By reducing the high dislocation density and promoting the formation of reverted austenite, the SCA treatment creates a recovered, low‐defect substrate. This dictates the formation of a Cr ₂ O ₃ ‐dominated passive film with low electronic defect density (low N _D ), in contrast to the hydroxide‐rich film on the SA‐treated state. The SCA‐treated specimen exhibits a recovered pitting potential, the highest repassivation potential, suppressed metastable pitting, and the highest polarization resistance, while retaining high hardness after a strategic compromise from the SA peak. This work demonstrates that 760°C conditioning enables a paradigm shift from a corrosion‐susceptible, strength‐prioritized state to a synergistically optimized one, offering a new principle to overcome the strength‐corrosion trade‐off in additively manufactured high‐performance steels.