Sulfide Stress Cracking Resistance Research Articles

Simultaneous Enhancement of Strength and Sulfide Stress Cracking Resistance of Hot-Rolled Pressure Vessel Steel Q345 via a Quenching and Tempering Treatment.

Sulfide stress cracking (SSC) failure is a main concern for the pressure vessel steel Q345 used in harsh sour oil and gas environments containing hydrogen sulfide (H2S). Methods used to improve the strength of steel usually decrease their SSC resistance. In this work, a quenching and tempering (Q&T) processing method is proposed to provide higher strength combined with better SSC resistance for hot-rolled Q345 pressure vessel steel. Compared to the initial hot-rolled plates having a yield strength (YS) of ~372 MPa, the Q&T counterparts had a YS of ~463 MPa, achieving a remarkable improvement in the strength level. Meanwhile, there was a resulting SSC failure in the initial hot-rolled plates, which was not present in the Q&T counterparts. The SSC failure was not only determined by the strength. The carbon-rich zone, residual stress, and sensitive hardness in the banded structure largely determined the susceptibility to SSC failure. The mechanism of the property amelioration might be ascribed to microstructural modification by the Q&T processing. This work provides an approach to develop improved strength grades of SSC-resistant pressure vessel steels.

Sulfide stress cracking (SSC) of a commercial Q345 pressure vessel steel in a wet H2S environment

The steel Q345 is extensively used in pressure vessels with low and medium pressure because of good mechanical properties and low cost. Good resistance to sulfide stress cracking (SSC) is required for the pressure vessel steel, but the SSC behavior of the Q345 has received little attention. This work investigated the SSC behavior of the Q345 in a wet H2S environment. The microstructure contained the irregular various-sized polygonal-like ferrite grains plus a carbon-rich degenerate pearlite banded structure. The Q345 had high ductility but failed to pass the SSC tests. The SSC cracking involved hydrogen embrittlement. The SSC preferentially occurred at the carbon-rich degenerate pearlite banded structure. The elimination of the carbon-rich degenerate pearlite banded structure is necessary to improve the SSC resistance of the Q345 pressure vessel steel.

Bridge for the thermodynamics and kinetics of electrochemical corrosion: Designing a corrosion–resistant HP–13Cr stainless steel by Cu alloying for use in an H2S–containing geothermal environment

The dissolution–ionization–diffusion–deposition (DIDD) model was used for developing a corrosion–resistant stainless steel (SS) by the means of alloying and the guidelines for the process were proposed. The novel HP–13Cr–Cu SS was designed to resist corrosion in H2S–containing geothermal environment. The results indicated that the preferential deposition of CuS promoted the heterogeneous nucleation rate of Cr2O3, FeCr2O3, and FeS, which formed denser corrosion product layer. As a result, this alloy exhibited a low corrosion rate and a high sulfide stress cracking (SSC) resistance. The results were consistent with the theoretical calculation conducted by the DIDD model.

Effect of Cooling Rate on Sulfide Stress Cracking Resistance of a Q345 Pressure Vessel Steel Subject to Hydrogen Sulfide

As an important equipment for the separation, store, and transport of the oil and natural gas in energy industry, the pressure vessels are subjected to harsh service environments of sulfide stress cracking (SSC). In this work, the effect of the cooling rate on the SSC susceptibility of a Q345 pressure vessel steel is studied. A pronounced distinction in microstructure is presented as the cooling rate is increased from ≈1 to ≈15 °C s−1. At ≈1 °C s−1, the microstructure is consisted of polygonal‐like ferrite and distinct banded pearlite. At ≈5 °C s−1, the microstructure is consisted of polygonal‐like ferrite and faintly banded pseudo‐pearlite. At ≈15 °C s−1, the microstructure is acicular ferrite with a complete elimination of banded structure. The cooling rate decides the level of the banded structure. As the cooling rate increases, the banded structure becomes relatively slight and even disappears. Strength in sort ascending is ≈1, ≈ 5, and ≈15 °C s−1. The SSC failure happens at ≈1 and ≈5 °C s−1, while does not happen at ≈15 °C s−1. The strength is not the only dominant factor responsible for the SSC failure. The SSC is preferentially generated at the banded structure. The elimination of the banded structure is necessary to improve the SSC resistance of the Q345 pressure vessel steel.

Effect of double tempering process on sulfide stress cracking susceptibility in API-5CT-C110 casing steel

The sulfide stress cracking (SSC) of the API-5CT-C110 grade casing steel in this work was evaluated by double cantilever beam (DCB) testing, two thermal treatments were used to investigate microstructures and properties. Compared to one, long-term tempering treatment, the study showed that precipitate size and dislocation density significantly decreased if two, short-term tempering treatments were used instead. DCB testing showed that SSC resistance is improved by double tempering with no degradation of strength. Specimens treated by double tempering have a lower proportion of Σ3 boundary, high-angle grain boundaries and high Taylor factor values, reduced susceptibility to crack initiation and propagation.

An Investigation of Microstructure Characteristic and Sulfide Stress Cracking Behavior of 110 ksi Cr-Mo Grade Casing Steel

The sulfide stress cracking (SSC) behavior of three micro-alloying 110 ksi grade Cr-Mo casing steels were evaluated according to the A-Method tensile test specified in the NACE TM0177 standard (NACE A-method). The fractures of SSC specimens and the micro-structures of the casing steels were characterized by scanning electron microscopy (SEM) with electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM) in the BF and STEM mode. The results show that on the premise of 110 ksi, the yield strength of Co-Mo steel was satisfactory, finer spherical carbides increased the number of irreversible traps; widened polygonised martensitic laths, lowered dislocation density, and lowered the proportion of high-angle grain boundaries and the Σ3 boundaries decreased hydrogen permeability and diffusivity. The SSC resistance of Co-Mo steel with above micro structure characteristics was enhanced.

Modification of Inclusions by Rare Earth Elements in a High-Strength Oil Casing Steel for Improved Sulfur Resistance

Steel casing pipes used in the construction of deep oil wells usually require both high strength and corrosion-resistant behavior. Due to the exploration of deep H2S-bearing oil reservoirs, sulfide stress cracking (SSC) is becoming an increasingly serious concern for casing steel. The nonmetallic inclusions in the steel are among the key reasons for its service failure. The rare earth element Ce can be used to modify the inclusions in casing steel and improve its SSC resistance. Here, taking C110 grade casing steel (the highest class currently in service) as the investigated object, the modification behavior of Ce inclusions in the steel and the effect of the addition of Ce in varying amounts (0.01, 0.024, and 0.042 wt.%) on the modified products were studied through high-temperature tube furnace experiments and thermodynamic calculations. The results showed that Ce had an obvious modification effect on the CaO·Al2O3 inclusions in casing steel, and the diffusion of dissolved Ce in the steel was the limiting step of the modification reaction. With the extension of reaction time, the sequence describing the modification of inclusions in the steel was determined as follows: CaO·Al2O3 → CeAlO3 → Ce2O3/Ce2O2S. The final stable product after modification depended on the amount of Ce added. With 0.01 wt.% Ce, the stable phase in molten steel was Ce2O3; on the other hand, upon adding ≥0.024 wt.% Ce, the stable phase became Ce2O2S. In addition, the thermodynamic stability of Ce2O3 decreased, and it was transformed into CeAlO3, Ce2O2S, Ce2S3, and CeS during solidification. On the basis of our results and the considerations for smooth casting, the addition of a proper amount of a rare earth element is suggested for industrial trials, following the achievement of a significant and surprising improvement in the qualified rate of SSC resistance for the final steel products. The relevant mechanism is also analyzed.

Особенности микроструктуры и микротекстуры среднеуглеродистой стали, подвергнутой сероводородному растрескиванию под напряжением

Increasing the resistance of steel products to sulfide stress cracking (SSC) is one of the topical issues of the oil and gas industry. Among various factors determining the SSC resistance of a material is the structure-phase state of the material itself and the crystallographic texture associated with it. This paper analyzes these features using the scanning electron microscopy (SEM), transmission electron microscopy (TEM), and microroentgen electron backscattered diffraction (EBSD) techniques. As the research material, a production string (PS) coupling made of medium-carbon steel was selected, which collapsed by the mechanism of hydrogen embrittlement and subsequent SSC. For the first time, by the SEM method, using the location and mutual orientation of cementite (Fe3C) particles, at high magnifications, the authors demonstrated the possibilities of identifying the components of upper bainite, lower bainite, and tempered martensite in steels. The presence of the detected structural components of steel was confirmed by transmission electron microscopy (TEM). Using the EBSD method, the detailed studies of microtexture were conducted to identify the type and nature of the microcrack propagation. It is established that the processes of hydrogen embrittlement and subsequent SSC lead to the formation of {101} <0¯10>, {100} <001>, {122} <2¯10>, {013} <211>, {111} <¯100>, {133} <1 ̅2 ̅1>, {32 ̅6 ̅} <201> grain orientations. It is shown that the strengthening of orientations of {001} <110>, {100} <001>, {112} <111>, and {133} <1 ̅2 ̅1> types worsens the SSC resistance of the material. Using the EBSD analysis method, the influence of coincident site lattice (CSL) grain boundaries on the nature of microcrack propagation is estimated. It is found that the Σ 3 CSL grain boundaries between the {122} <2¯10> and {111} <¯100>, {012} <1 ̅1 ̅0>, {100} <001> plates of the upper bainite inhibit the microcrack development, and the Σ 13b, Σ 29a, and Σ 39a CSL grain boundaries, contribute to the accelerated propagation of microcracks. For comparative analysis, similar studies were carried out in an unbroken (original) coupling before operation.

Effect of Zr Microalloying on Sulfide Stress Cracking Resistance in 125ksi Grade Oil Country Tubular Goods Steel

Effect of Zr Microalloying on Sulfide Stress Cracking Resistance in 125ksi Grade Oil Country Tubular Goods Steel

Effects of Ce and La on microstructure and sulfide stress cracking susceptibility of API-5CT-C110 casing steel

This study investigated the effects of Ce and La addition on microstructure and sulfide stress cracking (SSC) behavior of API-5CT-C110 casing steel. The role of rare earth (RE) elements on the SSC resistance was assessed via uniaxial tensile testing and double cantilever beam testing (NACE TM0177 A and D methods). The experimental results show that the appropriate addition of RE is beneficial to the improvement of SSC resistance without compromising strength. RE addition is found to refine prior austenite grains and carbides, and modify the coarse inclusions into spherical RE oxysulfides. The electron backscattered diffraction analysis indicates that the steel with RE has lower high angle grain boundary and kernel average misorientation, which could effectively hinder crack propagation and thus reduce the SSC susceptibility. Furthermore, the proportion of deformed grains is reduced significantly due to RE addition, and substructure grains with low storage energy are increased, which is also a vital factor enhancing the SSC resistance.

On the sulfide stress cracking resistance of a 125 ksi grade high-strength low-alloyed steel for oil country tubular goods

Excellent sulfide stress cracking (SSC) resistance was achieved in a 125 ksi grade high-strength low-alloyed steel with increased C content and Cu alloying. Results showed that increased C content allowed tempering at higher temperature, obtaining low dislocation density without decreasing strength. Moreover, Cu alloying refined martensite blocks and inhibited dislocation annihilation, but hardly influenced the precipitation of Cr-rich carbides. The decrease in dislocation density was the main reason for improving SSC resistance, and sufficient precipitation of Cr-rich carbides came in second. Despite Cu alloying failing to improve the SSC resistance, it increased the yield strength without sacrificing SSC resistance.

The Effects of NaCl on Hydrogen Permeation and Sulfide Stress Cracking Resistance of C110 High-strength Steel

Sulfide stress cracking (SSC) limits the application of high-strength low-alloy carbon steel C110 in the oil and gas industries. Chloride ions (Cl−) play an indispensable role in SSC. This study aims to evaluate the effects of NaCl on hydrogen permeation and SSC susceptibility by electrochemical techniques including hydrogen permeation test and electrochemical impedance spectroscopy (EIS), and the novel notched tensile slow strain rate test on carbon steel C110 under wet-H2S environments. The results show that the higher concentration of Cl− reduces hydrogen absorption and enhances SSC susceptibility. However, it is widely accepted that the reduction in hydrogen absorption results in an increase in SSC resistance. To figure out the role of Cl− in the SSC mechanism, the morphology of the side and the cross-sectional surface were observed. It was found that a higher pit density in a condition with a higher Cl− concentration leads to increased SSC susceptibility as pits act as crack initiation sites. The SSC mechanism transfers from hydrogen embrittlement to pit-induced cracking when the Cl− concentration in the solution increases.

Hydrogen embrittlement of high-strength API carbon steels in H2S and CO2 containing environments

This study aims to understand the Sulfide Stress Cracking (SSC) resistance of API carbon steels exposed to wet sour environments containing CO2. A mini-pipe specimen was cut from API grade tubulars and placed in an SSC test cell to perform the investigation. The specimen was highly strained and internally pressurized while exposed to the corrosive environment for seven days. The partial pressure ratio (PPR) of CO2 (i.e. ratio of partial pressure of CO2 to the total pressure) was varied to study the effect of CO2 content on SSC. Experiments were performed while maintaining a constant H2S concentration and temperature. The steels' variations in mechanical properties (ultimate tensile strength and plastic strain before failure) after exposure to the sour environment are used to quantify the embrittlement. In addition, the specimens were examined using optical microscopes to assess the severity of the SSC corrosion based on shear deformation patterns and crack features. The SSC resistance of the tested steels was minimized when the PPR of CO2 was approximately 20%. Results demonstrate that the materials have adequate SSC corrosion resistance to be utilized in the environment containing 280 ppm H2S. Nevertheless, their SSC resistance reduced noticeably between 10 and 30% PPR of CO2.

Effect of Tempering Temperature on Microstructure and Sulfide Stress Cracking of 125 Ksi Grade Casing Steel.

The influence of tempering temperature on the microstructure of 0.5Cr0.4W steels was investigated by scanning electron microscope, and the roles of grain boundary character, dislocation, and Taylor factor in sulfide stress cracking (SSC) resistance were interpreted using the election backscattered diffraction technique. The 0.5Cr0.4W steels tempered at 690 °C, 700 °C, and 715 °C all showed tempered martensites. The specimen tempered at 715 °C exhibited a higher critical stress intensity factor (KISSC) of 34.58 MPa·m0.5, but the yield strength of 800 MPa did not meet the criterion of 125 ksi (862 MPa) grade. When the specimen was tempered at 690 °C, the yield strength reached 960 MPa and the KISSC was only 21.36 MPa·m0.5, displaying poorer SSC resistance. The 0.5Cr0.4W steel tempered at 700 °C showed a good combination of yield strength (887 MPa) and SSC resistance (KISSC: 31.16 MPa·m0.5). When increasing the tempering temperature, the local average misorientation and Taylor factor of the 0.5Cr0.4W steels were decreased. The reduced dislocation density, and greater number of grains amenable to slippage, produced less hydrogen transport and a lower crack sensitivity. The SSC resistance was, thus, increased, owing to the minor damage to hydrogen aggregation. Therefore, 700 °C is a suitable tempering temperature for 0.5Cr0.4W casing steel.

Comparison of 2507 Duplex and 28 % Cr- Austenitic Stainless Steel Corrosion Behavior for High Pressure and High Temperature (HPHT) in Sour Service Condition with C-ring Experiment

The scarcity of oil and gas resources made High Pressure and High Temperature (HPHT) reservoir attractive to be developed. The sour service environment gives an additional factor in material selection for HPHT reservoir. Austenitic 28 Cr and super duplex stainless steel 2507 (SS 2507) are proposed to be a potential materials candidate for such conditions. C-ring tests were performed to investigate their corrosion behavior, specifically sulfide stress cracking (SSC) and sulfide stress cracking susceptibility. The C-ring tests were done under 2.55 % H2S (31.48 psia) and 50 % CO2 (617.25 psia). The testing was done in static environment conditions. Regardless of good SSC resistance for both materials, different pitting resistance is seen in both materials. The pitting resistance did not follow the general Pitting Resistance Equivalent Number (PREN), since SS 2507 super duplex (PREN > 40) has more pitting density than 28 Cr austenitic stainless steel (PREN < 40). SS 2507 super duplex pit shape tends to be larger but shallower than 28 Cr austenitic stainless steel. 28 Cr austenitic stainless steel has a smaller pit density, yet deeper and isolated.

Sulfide Stress Cracking of C-110 Steel in a Sour Environment

The scope of this study includes modeling and experimental investigation of sulfide stress cracking (SSC) of high-strength carbon steel. A model has been developed to predict hydrogen permeation in steel for a given pressure and temperature condition. The model is validated with existing and new laboratory measurements. The experiments were performed using C-110 grade steel specimens. The specimens were aged in 2% (wt.) brine saturated with mixed gas containing CH4, CO2, and H2S. The concentration H2S was maintained constant (280 ppm) while varying the partial pressure ratio of CO2 (i.e., the ratio of partial pressure of CO2 to the total pressure) from 0 to 15%. The changes occurring in the mechanical properties of the specimens were evaluated after exposure to assess material embrittlement and SSC corrosion. Besides this, the cracks developed on the surface of the specimens were examined using an optical microscope. Results show that the hydrogen permeation, and subsequently SSC resistance, of C-110 grade steel were strongly influenced by the Partial Pressure Ratio (PPR) of CO2 when the PPR was between 0 and 5%. The PPR of CO2 had a limited impact on the SSC process when it was between 10 and 15 percent.

Effects of thermal spray aluminium coating on SSC and HIC resistance of high strength steel in a sour environment

Flexible risers are critical equipment for the production of oil and gas in offshore fields around the world. The annulus region may condense acidic water containing H2S exposing the tensile armour steel wires to a sour environment, which may promote sulphide stress cracking (SSC) and/or hydrogen-induced cracking (HIC). This work aims to evaluate through electrochemical and constant displacement tests the effectiveness of thermal spray aluminium (TSA) coating to mitigate SSC and HIC in high strength steel used to manufacture the tensile armour of a flexible riser. Electrochemical tests confirmed the anodic behaviour of the coating against the steel and estimated a service life of 2.5 years. The constant displacement test indicated that the non-coated samples failed by SSC although some cracks were also found in the samples mid-section due to HIC. For Al-coated samples, no signs of SSC and HIC were observed. The TSA coating showed a dual barrier effect, hindering either corrosion of steel or hydrogen up-taking, and neither SSC nor HIC was observed. Samples with a coating defect were cathodically protected and no HIC was observed.

Sulphide stress cracking behaviour of the coarse-grained heat-affected zone in X100 pipeline steel under different heat inputs

The sulphide stress cracking (SSC) behaviour of a simulated coarse-grained heat-affected zone was investigated under different heat inputs. The microstructure and fracture surfaces were observed. SSC susceptibility was dominated by hydrogen embrittlement (HE) and, to a lesser extent, anodic corrosion. Heat input had a critical effect on the microstructure and material properties. When t8/5 (time taken to cool from 800 °C to 500 °C) was 30 s, the microstructure was mixed lath bainite/granular, with low HE and high SSC resistance. When t8/5 was 100 s, the microstructure was granular bainite, with high corrosion current density and low SSC resistance. The results provide guidance for development of SCC resistant welding procedures.

Effect of niobium on sulfide stress cracking behavior of tempered martensitic steel

Martensitic steels with increasing niobium (Nb) content from 0.003-0.060 wt.% were tempered at corresponding temperatures of 675−710 °C, consequently acquiring an almost identical yield strength of ∼780 MPa. The effect of Nb on the sulfide stress cracking (SSC) behavior was assessed via double cantilever beam testing, electrochemical permeation testing and microstructure characterization. The high Nb content and corresponding high-temperature tempering caused a more significant refinement of the martensitic packet/block with high-angle boundaries, which evidently inhibited SSC propagation; despite increased mobile hydrogen concentration which slightly promoted SSC propagation. The overall SSC resistance was therefore enhanced by increasing Nb content.

Influence of cooling path after rolling on sulfide stress cracking behavior for casing steel

Interrupted accelerated cooling (IAC) in comparison with normal air cooling after rolling is introduced into the production of the API-5CT-C110 casing steel. Sulfide stress cracking (SSC) resistance is improved by IAC processing without compromising strength. Multiple characterizations combined with hydrogen permeation tests are performed to reveal the mechanism of SSC behavior with respect to hydrogen interactions with metallurgical defects (grain boundaries, dislocations and precipitates). The results indicate a low dislocation density and increased amount of irreversible traps are responsible for the superior SSC resistance of the IAC specimen. A model of local hydrogen concentration is proposed to illustrate SSC susceptibility.