Additive manufacturing (AM), specifically Laser Powder Bed Fusion (LPBF), brings benefits to the Oil & Gas industry in the areas of better performance, inventory management, and cost reduction. However, selection of AM alloy UNS(1) N07718 (AM 718) face uncertain material capabilities for critical applications such as sour service, when compared to its wrought counterpart specified in API(2) 6ACRA (oilfield 718). This study reveals that AM 718 of modified solution treatment combined with standard API 6ACRA age hardening are capable of meeting the yield strength, tensile strength, elongation, and hardness requirements of API 6ACRA, with reduction of area of only 120K condition below the spec limit. AM 718 of modified solution treatment and API 6ACRA 120K age hardening shows resistance to environmentally assisted cracking (EAC) equivalent to oilfield 718 in slow strain rate (SSR) test per NACE TM0198-2020 at 300°F (149°C) in H2S-containing environment. The performance of AM 718 does not appear to be influenced by the powder conditions investigated. Results of this study provides data-supported clarity to the selection of AM 718 material conditions and production routes for Oil & Gas application and the H2S-service qualification.
AM brings significant benefits in better performance, inventory management, and lifecycle cost reduction to the Oil & Gas industry. Both manufacturers and users are working towards AM qualification and standardization in order to realize and sustain these benefits. Starting at the product level, the goal is to ensure the product is sound in its form, fit, and function, and free from macroscopic (surface, sub-surface, internal) anomalies deleterious to its performance. Product qualification is supported by a foundational metallurgical or AM material qualification.1
At the material qualification level, the goal is to satisfy the pre-established mechanical and metallurgical property targets of the material specification. Due to the lack of commonly accepted AM criteria, the industry opts to align with the requirements for wrought counterpart, for example, alloy UNS N07718 in API 6ACRA2 (oilfield 718). Data shows AM 718 is capable of meeting the oilfield 718 requirements albeit with larger variations than bar stocks.3 The uncertainties of qualifying AM 718 to be equivalent to oilfield 718 stem from the perceived variability of AM materials and processes.