Additive manufacturing unlocks complex designs, compresses lead times for the fabrication of nuclear reactor components. So far, most studies focused on laser powder bed fusion (LPBF) of austenitic stainless steel (i.e., 316 L), the exploration in LPBF of martensitic and precipitation-hardening (PH) steel remains limited for nuclear applications, particularly regarding their corrosion behavior. This study compared the corrosion performance of two PH steels (i.e.,17-4PH and CORRAX®) produced by casting and LPBF, respectively. For both steels, cast samples showed larger grain size, secondary δ-ferrite, and more precipitates, inducing more localized corrosion than LPBF-printed samples. In contrast, LPBF-printed samples exhibited refined grain size and homogeneous elemental distribution, enhancing corrosion resistance. To simulate primary coolant circuit crevice conditions during reactor off-cycle operations, immersion tests were conducted in 0.01 M HCl + 0.3 M NaCl solution at 25°C and 70°C. Based on weight loss, pit depth, and pit area measurements, the LPBF samples demonstrated less degradation than their cast counterparts. According to electrochemical characterization, cyclic polarization (CP) tests revealed higher pitting potentials, linear polarization resistance (LPR) tests indicated higher polarization resistance, and electrochemical impedance spectroscopy (EIS) showed a more protective oxide film contribution to charge transfer resistance in LBPF-printed than cast samples. Comparing between two steels, 17-4PH exhibited higher corrosion resistance and superior repassivation ability than CORRAX in LPR and CP tests. However, CORRAX demonstrated promising thermal stability, retaining better passive film integrity than 17-4PH according to CP and EIS analyses at 70°C. This study demonstrates the qualification and performance of LPBF-printed PH steels for use in corrosive nuclear reactor environments. • LPBF processing enhances corrosion resistance over casting for both 17-4PH and CORRAX steels in a simulated nuclear environment. • The rapid solidification of LPBF suppresses detrimental interphase boundaries and localized compositional gradients, eliminating primary micro-galvanic cells. • In LPBF CORRAX, refined grains enable rapid Cr diffusion and superior repassivation kinetics, arresting pit growth at inherent Al 2 O 3 inclusions. • An alloy-specific mechanism is identified: CORRAX forms an Al-enhanced stable oxide at 70 °C, while 17-4PH follows predictable Arrhenius-driven degradation. • This work demonstrates that LPBF provides not only geometric freedom but also intrinsic microstructural benefits-grain refinement and homogeneity-that are critical for corrosion resistance in nuclear applications.
Li et al. (Sun,) studied this question.