Sour Gas and Hydrogen Embrittlement Resistance of High-Strength UNS N07022 Alloy for Oil and Gas Applications Available to Purchase

ABSTRACT

N07022 is a Ni-21Cr-17Mo (wt.%) alloy that has found success in applications requiring corrosion resistance and high strength. The attributes of N07022 alloy in the cold-worked (CW) condition make it an excellent candidate for many oil and gas applications. It has been incorporated in the NACE MR0175 / ISO 15156 and NACE MR0103 / ISO 17945 standards at the highest test levels. It has also shown resistance to the NACE Level VII environment with 5 g/L elemental sulfur at 205°C (401°F) and to the demanding conditions of 25% NaCl + 1,000 psi (6.9 MPa) CO₂ + 1,000 psi (6.9 MPa) H₂S at 288°C (550°F). As higher strength alloys are becoming more common in high-pressure, high- temperature (HPHT) oil and gas service, there have been a number of reported failures involving precipitation-strengthened Ni-base alloys. These failures were attributed to hydrogen embrittlement. Recent results of sour gas and hydrogen embrittlement testing of CW N07022 alloy will be presented. The test results of CW N07022 alloy will demonstrate that it offers superior properties to precipitation- strengthened Ni-base alloys for demanding oil and gas applications.

INTRODUCTION

UNS N07022 alloy, known commercially as HASTELLOY^† C-22HS^† alloy, is a Ni-21Cr-17Mo (wt. %) alloy that exhibits an excellent combination of material properties.¹ The nominal chemical composition of N07022 alloy is provided in Table 1. Similar to other Ni-Cr-Mo “C-type” alloys, which contain high levels of both Cr and Mo, N07022 alloy exhibits excellent resistance to uniform and localized corrosion in both oxidizing and reducing acids. In addition, N07022 alloy provides very high strength in the cold-worked (CW) condition. Room temperature (RT) yield strength levels of 180 ksi are commonly achieved in CW bar and tubular material.^2,3

N07022 alloy has been incorporated in the NACE MR0175 / ISO 15156 and NACE MR0103 / ISO 17945 standards at the highest test levels. It has also exhibited resistance to the NACE Level VII environment with 5 g/L elemental sulfur at 205°C (401°F) and to the demanding conditions of 25% NaCl + 1,000 psi (6.9 MPa) CO₂ + 1,000 psi (6.9 MPa) H₂S at 288°C (550°F).² This superior sour gas resistance, in combination with excellent mechanical properties, makes CW N07022 alloy well-suited for demanding oil and gas applications.