Comparative Evaluation of Additively Manufactured and Forged Low Alloy Steel for Subsea Applications (RIP2026-00068)

Marcella Lage, Fabio Alves, Victor Hugo Oliveira, Mateus Porto, Ravi Kapur, Christopher Irving, Carlos Eduardo Fortis Kwietniewsi, Marcelo Sartori, Tiago Samuel Renck

, TechnipFMC, TechnipFMC plc, TechnipFMC plc, TechnipFMC, Universidade Federal do Rio Grande do Sul, Universidade Federal do Rio Grande do Sul, Universidade Federal do Rio Grande do Sul

The Oil & Gas industry faces challenges in adopting Additive Manufacturing (AM) for critical components such as pressure-containing, pressure-controlling, and structural load-bearing parts. This is limited by the lack of standardization and insufficient validation of performance equivalence to wrought materials particularly regarding mechanical properties and behavior under subsea conditions, including seawater and H2S exposure.
This study presents a comparative assessment of low alloy steel (LAS) produced by forging and by Direct Energy Deposition with Wire Arc (DED-Arc). The evaluation includes metallurgical and mechanical properties, with emphasis on environmentally assisted cracking (EAC) performance, benchmarked against the DNV-RP-0034 standard for forged components.
To assess hydrogen-induced stress cracking (HISC) susceptibility under cathodic protection in seawater, specimens were tested using rising displacement and incremental step loading with load control (ISL-LC). ISL-LC serves as an alternative fracture mechanics method for K threshold determination. Results showed that properly processed AM material exhibits comparable microstructure, mechanical properties, and EAC performance to forged LAS under these conditions. This data builds confidence in AM material, even with potential flaws, fostering its use in critical applications.