UNS N08935 - A New Versatile Grade for OG

摘要

UNS N08935 is a new versatile austenitic alloy with the composition 35Ni-30Fe-27Cr-6.5Mo-0.28N and a PREN of 52. It has an extreme pitting resistance which makes the grade a good candidate for O&G applications. The alloy is available in several strength levels with good ductility: seamless tubes with 62 ksi, 140 ksi and 180 ksi. It is an austenitic grade that is worked to strength which results in an alloy with very high resistance to hydrogen effects. According to NACE MR0175 / ISO 15156 the grade will be a Type 4c material. For the 62 ksi material the resistance against Hydrogen Induced Stress Cracking (HISC) has been demonstrated by constant load testing of specimens polarized to -1050 mV_(SCE). For the cold worked material Slow Strain Rate Testing (SSRT) at Test Level Ⅵ in NACE MR0175 / ISO 15156, a condition within Type 4d is discussed. With its high mechanical strength and pitting resistance as well as being not prone for HISC, UNS N8935 is an interesting candidate for subsea applications. Further, UNS N08935 is interesting as tubing for HPHT-wells due to its very high strength.