Inconel X750 (UNS N07750) and NACE MR0175

Inconel X750 (UNS N07750) is a precipitation-hardened nickel-based alloy listed in NACE MR0175 / ISO 151656 part 3 tables A.35 and A.36 as a valid material for non-pressure containing components and springs. This material was previously approved as a nickel-chromium alloy in NACE MR0175-2002 and is still listed as an approved precipitation-hardenable nickel alloy in NACE MR0103.

Question 1: Can Inconel X750 Be Used as a Pressure Boundary Component in Any NACE MR0175 Application?

Answer 1: No, Inconel X750 is prohibited from use as a pressure boundary component for any NACE MR0175 application under any conditions.

Question 2: Why was Inconel X750 Removed from NACE MR0175?

Answer 2: Inconel X750 was removed during the NACE MR0175 2003 rewrite and this was also carried over in NACE MR0175/ISO 15156 in 2003. Although there is no definitive answer as to why it was removed, the alloy is known to be susceptible to hydrogen embrittlement and has experienced failures. Two resources listed as references for further information are “”H₂S Corrosion in Oil & Gas Production: A Compilation of Classic Papers, NACE, 1981″” and NACE Corrosion 2003 conference paper 03133.

This inquiry pertains to NACE MR0175 part 3 A.9 and is in reference to Maintenance Panel Inquiry #2015-15. Please contact our team to discuss the use of Inconel X750.