AISI 420 modified (13Cr) martensitic stainless steels are often chosen for the manufacture of downhole completion equipment within the oil and gas production environment. 13Cr is primarily used in CO2 rich production environments where carbon/low-alloy steels are subjected to high corrosion rates. The material is available as both bar stock and tubing. Bar stock is predominantly used for manufacturing thick-walled completion tool components. 13Cr material that has been quenched and tempered to 22 HRC maximum hardness provides resistance to sulfide stress cracking (SSC) in environments with low hydrogen sulfide (H2S) levels; it is typically used to a maximum H2S limit of 10 kPa (1.5 psi) in accordance with the NACE MR0175/ISO 15156-3 guidelines.1 For H2S levels exceeding 10 kPa (1.5 psi), the primary option for completion tools is the use of precipitation hardenable nickel alloys, such as Alloy 925 and Alloy 718. These nickel alloys can also be obtained as bar stock, but they are significantly more expensive than 13Cr.

This paper discusses a study wherein the SSC resistance of 13Cr bar stock quenched and tempered to 22 HRC maximum hardness was tested and evaluated beyond the maximum H2S limit of 10 kPa (1.5 psi) established in NACE MR0175/ISO 15156-3 for use in sour service. The SSC testing simulated various H2S levels and was performed on various heats, bar stock material sizes, and hot-work ratios. The SSC results showed that 13Cr material quenched and tempered to 22 HRC maximum hardness exhibits cracking resistance at H2S levels up to 100 kPa (14.5 psi), depending on pH and salinity conditions. This performance indicates this material can be used for downhole equipment in certain oil and gas production well conditions where the alternative options would be the more expensive nickel alloys.

Subject
Test methods, Materials, Microscopy, Nickel based alloys, Tools, Reservoirs, Maximum hardness, Heat, Water injection, Pitting, Cracking, Sulfide stress cracking, Quenching and tempering
Keywords:
Sulfide Stress Cracking (SSC), AISI 420 modified (13Cr), stainless steel, bar stock, H2S, NACE MR0175, ISO 15156
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2017
Association for Materials Protection and Performance (AMPP)
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