Comparison of hydrogen environment-assisted cracking behavior in additively manufactured and wrought 17-4PH stainless steel

The hydrogen environment-assisted cracking (HEAC) behavior of additively manufactured (AM) and wrought 17-4PH stainless steel heat treated to exhibit similar microstructure and yield strength is assessed through fracture mechanics-based testing conducted in 0.6 M NaCl at an applied potential of -1.1 V_SCE (vs. saturated calomel). Results demonstrate that the HEAC susceptibility of the AM 17-4PH is notably increased relative to the wrought material. These data are coupled with measured hydrogen-metal interaction parameters and microstructural observations for each alloy to understand the origins of the increased susceptibility. Results collectively demonstrate that sub-micrometer porosity present in the AM material is providing a primary contribution to the degradation in HEAC resistance. The mechanistic basis for the influence of porosity is considered in the context of an existing model for HEAC. The implications of these findings on the broader AM community are then discussed.