Abstract
Ni-base precipitation hardened (PH) superalloys are used in oil and gas applications where a combination of corrosion resistance and excellent mechanical properties are required. Hydrogen is often present in these situations due to cathodic protection, unintended galvanic coupling, or the application environment. These alloys have shown to be susceptible to hydrogen environment assisted cracking (HEAC), leading to reported early failures in the field. In this study, alloys UNS N07716, UNS N09925, and UNS N07718 were examined in various conditions to further understand the role of microstructure and processing on the severity of degradation caused by hydrogen in Ni-base PH superalloys. Both rising step load bend testing and slow strain rate tension testing were used to measure HEAC resistance. Specimens were exposed to hydrogen via application of in-situ cathodic polarization in 3.5 wt% NaCl aqueous solution. Alloy processing variations included warm working and heat treatments to intentionally modify grain size and precipitation. Results indicated the severity of hydrogen damage was affected by the alterations in processing and microstructure as well as the measured strength of the material.
