Influence of Postbuild Microstructure on the Electrochemical Behavior of Additively Manufactured 17-4 PH Stainless Steel

Abstract

The additive manufacturing (AM) build process produces a segregated microstructure with significant variations in composition and phases that are uncommon in traditional wrought materials. As such, the relationship between the post-build microstructure and the corrosion resistance is not well understood. Stainless steel alloy 17-4PH is an industrially-relevant alloy for applications requiring high-strength and good corrosion resistance. A series of potentiodynamic scans conducted in a deaerated 0.5 mol/L NaCl solution evaluated the influence of these microstructural differences on the pitting behavior of SS17-4. The pitting potentials were found to be higher in the samples of additively-processed material than in samples of the alloy in wrought form. This indicates that the additively-processed material is more resistant to localized corrosion and pitting in this environment than the wrought alloy. The results also suggest that after homogenization, the additively-produced SS17-4 could be more resistant to pitting than wrought SS17-4 in an actual service environment.

Corrosion of Additively Manufactured Alloys: A Review

“…The tabulation of such studies are presented in Table 4. 61,64,[73][74][75][76][77]80,[82][83]86,[95][96][97][98][99][100][101][102][103][104] Environments containing chloride ions are well known to be detrimental to the durability of stainless steels, with a number of studies tabulated above appropriately focusing on such electrolytes. 105 In a study by Ganesh, et al, 95 two batches of specimens (termed "A" and "B") were produced via DLD, by utilizing similar parameters to produce Type 316L specimens.…”

“…The corrosion of precipitation hardened 17-4 PH (UNS S17400) stainless steels produced by SLM was investigated by Schaller, et al, 73 and Stoudt, et al, 101 in similar concentrations of NaCl solution (0.5 M and 0.6 M, respectively). Schaller, et al, analyzed the corrosion properties of SLM 17-4 PH as a function of porosity and compared the results with their wrought counterpart.…”

Laser Powder Bed Fusion of Precipitation-Hardened Martensitic Stainless Steels: A Review

“…The above differences in microstructure explain the changes in hardness shown in Figure 13. Previous investigations of L-PBF 17-4 PH stainless steels focused on evaluating the heat treatment response of as-built material through hardness measurements in the solutionized [27,129,136,137], solutionized and aged [27,93,129,136], and aged only conditions [27,95,96], as shown in Table 6. The L-PBF + SHT specimen exhibited higher hardness values than the As-L-PBF sample.…”

Material-process-property relationships of 17-4 stainless steel fabricated by laser-powder bed fusion followed by hot isostatic pressing.

“…At the energy density of 104 J/mm 3 , the corrosion performance is independent of starting powder characteristics (shape and size) and atomization method (gas or water-atomization) used to produce these powders. stainless steel is used in many applications that take advantage of its high mechanical properties in combination with its excellent corrosion resistance [26], [84], [90], [101], [104], [107]. Several research studies have been carried in our group as well as literature to fabricate defect-free L-PBF parts from 17-4 PH stainless steel and enhance the resulting mechanical properties using the post-processing operations such as hot isostatic pressing (HIP) and heat-treatment [2], [3], [6], [8], [15], [32], [50], [51], [56]- [69].…”

“…Other studies have indicated how microstructural features can also affect the corrosion properties of post-processed [32], [40]- [42]L-PBF parts [87], [109], [112], [113]. For example, Ralston and Birbilis [114] was finished by diamond polishing using a 1µm grade medium.…”