13Cr-5Ni-2Mo type Super Martensitic stainless steels referred to as SMSS-13Cr type grades can provide good general corrosion resistance such as in high CO₂ environments combined with higher strengths and excellent toughness² making them a prospective material choice for long term downhole completion equipment depending on actual well conditions. One of the main limiting factors for the use of SMSS-13Cr type grades is the Sulfide Stress Cracking (SSC) resistance in presence of H₂S in downhole well conditions. Therefore, a good understanding of this behavior is essential to facilitate the material selection process. 

Martensitic stainless steel (MSS) well tubulars are favorable due to their high strength and relatively low cost and are therefore widely applied in the Oil & Gas industry. This is especially the case for 13Cr and Super13Cr grades, which are often selected for mildly sour gas fields, where a relatively low content of H₂S is present. When selecting martensitic stainless steels for sour service, the susceptibility to Stress Corrosion Cracking (SCC) and Sulfide Stress Cracking (SSC), determined by standard laboratory tests, are the most important selection criteria.

In martensitic stainless steel used in H2S-saturated condition SSC is regarded as a main concern rather than SCC in material selection for each specific well condition. In this paper by adding hydrogen embrittlement results at elevated temperature environmentally-assisted cracking (EAC) data of SSC and SCC for are reported by using autoclave-based test results. The test condition is based on (1)temperature of 24C(75F) to 200C(392F) (2)20% and 5% NaCl solution (3)actual YS@in-situ as applied stress in four-point-bend-beam specimens (4)pH3.0@in-situ to pH5.0@in-situ which was adjusted by four factors of (a)partial pressure of 5MPa CO2 (b)partial pressure of 0.01MPa H2S (c)0.5%CH3COOH and CH3COONa addition as pH adjustment and (d)temperature.Judging from the domain maps of EAC for 13%Cr-added to 17%Cr-added martensite-based stainless steel OCTG materials the non-failure domain for each sample is limited by cracking and/or corrosion rate. In terms of cracking as testing temperature is higher each material has higher cracking-resistant. More precisely no SSC (SCC) happens anymore at the higher temperature than SSC (or SCC) begins not to occur when an autoclave test was carried out by elevating temperature from room temperature (24C 75F). In terms of corrosion rate it tends to have the higher value when an autoclave test is carried out at the higher temperature. The stability of passivation and protective surface layer on each stainless steel are related to the resistance for these two parameters. Higher-alloyed martensite-based stainless steel has better performance in both cracking and corrosion rate. In addition it was found that martensitic stainless steel do not have the specific cracking-susceptible temperature range at around 80C to 100C (175F to 210F) temperature which duplex stainless steel are said to specifically fail.