Stress Corrosion Cracking Sensitivity Research Articles

Influence of cathodic polarization on stress corrosion cracking susceptibility of 35CrMo steel for high strength bolt in simulated deep-sea environment

The effect of cathodic polarization on stress corrosion cracking (SCC) of 35CrMo steel for high strength bolt in the simulated deep-sea environment has been studied. The results show that 35CrMo steel has a higher SCC sensitivity at open circuit potential in the simulated deep-sea environment than that in the shallow seawater. With potential negatively shifted to −750 mV, 35CrMo steel presents the lowest SCC sensitivity. And the SCC susceptibility is increased significantly with the further negative shift of potential because of the intensive hydrogen evolution. When the potential is below −950 mV, hydrogen embrittlement with hydrogen-enhanced-plasticity mediated decohesion should be the dominant SCC micro-mechanism.

Influences of microstructures and macrozones on the stress corrosion cracking sensitivity of a near alpha titanium alloy

In this study, we investigated stress corrosion cracking (SCC) behaviors in a near alpha titanium alloy (Ti-6Al-3Nb-2Zr-1Mo) with distinct microstructures and microtextures. By analyzing fracture surfaces, crack growth paths, and grain orientations, we found that the SCC crack growth rate increased with an increase in the volume fraction of the primary αp phase, due to elevated crack initiation density and concentrated grain orientations. Additionally, SCC cracks exhibited a preference for propagating along boundaries between neighboring soft macrozones (easy for slip) and hard macrozones (relatively hard for slip), as well as through macrozones favorable for slip.

Effect of the triangular prism dent on stress corrosion cracking behavior of alloy 690TT heat transfer tube in a lead-containing alkaline solution

In this paper, the microstructural changes and mechanical characteristics of alloy 690TT heat transfer tube with a triangular prism dent are investigated by combining experimental and simulation methods, and subsequently examines their influence on stress corrosion cracking (SCC) behavior. The results indicate that the deformation mechanism caused by impact dent is slip and twinning. The structural transformation of high-density dislocations, as well as Copper and Brass deformation textures, are formed at dent bottom, resulting in stress concentration through work hardening, which greatly increases SCC sensitivity. Oxidation preferentially occurs along grain boundaries and dislocations, and the corrosion products are formed, which exhibit a semi-coherent orientation relationship with the matrix. Oxidation is essentially a de-alloying process in which oxygen diffuses inward and Cr migrates towards the oxidation zone. The wedge force generated by corrosion products provides another driving force for initiation and propagation of SCC cracks, in addition to external loads and residual stress. SCC cracks propagate in the form of intergranular stress corrosion cracking and transgranular stress corrosion cracking in a high temperature lead-containing alkaline solution.

Effect of surface hemispherical dent depth on the microstructure evolution and stress corrosion cracking of heat transfer tubes in steam generator

The deformation mechanism and SCC behavior of alloy 690TT with dents are investigated. Dents lead to stress concentration and microstructure changes, increasing stress corrosion cracking (SCC) sensitivity. The deformation mechanism at dents is slip and twinning. The dent shoulder zone experiences oxidation due to the residual tensile stress, whereas the dent bottom zone induces SCC due to the stress concentration, exhibiting a symmetrical distribution of “splayed character”. There is a critical threshold exists for dent depth that induces SCC, and the length of SCC cracks is positively correlated with dent depth in a power function.

Effect of Zn addition on the stress corrosion cracking of as-cast BCC Mg-11Li based alloys

The stress corrosion cracking (SCC) of ultralight Mg-11Li alloys with different Zn content revealed the obvious SCC sensitivity of mechanical ductility, while the mechanical strength is minimal. The less Zn (1 wt. %) addition can improve SCC resistance, while none (1 wt. %) or massive Zn (3, 6 wt. %) addition presents the opposite effect. The lowest SCC sensitivity of Mg-11Li alloy with 1 wt. % Zn is determined by the excellent surface film and insignificant micro-galvanic effect, while elevating Zn will enhance SCC sensitivity due to the considerable micro-galvanic effect induced by cathodic second phase and anodic β-Li matrix.

Stress corrosion cracking behavior of buried oil and gas pipeline steel under the coexistence of magnetic field and sulfate-reducing bacteria

Magnetic field and microorganisms are important factors influencing the stress corrosion cracking (SCC) of buried oil and gas pipelines. Once SCC occurs in buried pipelines, it will cause serious hazards to the soil environment. The SCC behavior of X80 pipeline steel under the magnetic field and sulfate-reducing bacteria (SRB) environment was investigated by immersion tests, electrochemical tests, and slow strain rate tensile (SSRT) tests. The results showed that the corrosion and SCC sensitivity of X80 steel decreased with increasing the magnetic field strength in the sterile environment. The SCC sensitivity was higher in the biotic environment inoculated with SRB, but it also decreased with increasing magnetic field strength, which was due to the magnetic field reduces microbial activity and promotes the formation of dense film layer. This work provided theoretical guidance on the prevention of SCC in pipeline steel under magnetic field and SRB coexistence.

Enhanced hydrogen induced stress corrosion cracking resistance of Ni-advanced weathering steel by Ni and Mn modification

The stress corrosion cracking (SCC) behavior of three kinds of Ni-advanced weathering steel and a common weathering steel are examined in a simulated harsh marine environment by X-ray diffraction, scanning electron microscopy, electron backscattered diffraction, transmission electron microscopy, electrochemical tests, and slow strain rate tensile tests under different applied potentials. The results show that the SCC susceptibility of all test steel is low at open circuit potential. However, the SCC sensitivity of the conventional weathering steel increases significantly at − 1200 mV, while the Ni-advanced weathering steel exhibits good resistance to hydrogen embrittlement, which is attributed to the improved stacking fault energy, decrease of martensite-austenite constituents and refined grain size caused by increase in Ni and Mn content.

Study on stress corrosion properties of aviation aluminum alloy friction stir welded joint at the different strain rate

Aviation aluminum alloy welded structures are subjected to stresses at different strain rates in corrosive environments such as the ocean. Studying the stress corrosion properties of aviation aluminum alloy Friction Stir Welding (FSW) structures is essential. Therefore, this paper focuses on the study of 12 mm thick 7085-T7452 high-strength aviation aluminum alloy FSW joints under different strain rates of stress corrosion properties changes and the impact of welding process parameters. The main conclusions of this thesis are as follows: For the base material (BM) and the aluminum alloy FSW joints, when the strain rate increased from 10−7 s−1 to 10−5 s−1, the stress corrosion strength increased, and the stress corrosion cracking (SCC) sensitivity index ISSRT decreases. The SCC sensitivity at the same strain rate: SS-400-120 > SS-300-60 > SS-300-120 > BM. After the Slow strain rate tensile (SSRT) test, the FSW joint fracture in the air is a transgranular ductile fracture. Meanwhile, the fracture is a ductile-brittle hybrid fracture in 3.5% NaCl solution, and the number of secondary cracks along the grain boundary increased significantly, showing obvious SCC sensitivity. The BM fracture after SSRT is ductile, showing lower SCC sensitivity.

Effect of MgF2 coating on stress corrosion cracking behavior of Mg−Zn−Ca alloy in simulated body fluid

The stress corrosion cracking behavior of Mg−3wt.%Zn−0.2wt.%Ca (MZC) alloy and fluoride (MgF2) coated Mg−3wt.%Zn−0.2wt.%Ca alloy (MZC-MF) for bone implant applications was investigated using slow strain- rate tensile (SSRT) tests in simulated body fluid (SBF). The results show that MgF2 coating could significantly improve the corrosion resistance and prolonged fracture failure time of MZC alloy. MgF2 coating also greatly reduced the stress corrosion cracking sensitivity of MZC alloy in SBF. Compared to MZC alloy, stress corrosion cracking sensitivity index (Iscc) of MZC-MF alloy decreased by 21% (ultimate tensile strength, UTS), 22% (time to failure, tf), 23% (elongation after fracture, δ), 7% (reduction ratio of cross-sectional area after fracture, ϕ) and 15% (inner product work, A), respectively.

Effects of load waveforms on stress corrosion behavior of pipeline steel

The effects of different load waveforms on stress corrosion cracking (SCC) of X70 pipeline steel were studied by means of fluctuating slow strain rate tensile test (F-SSRT). The results show that the SCC sensitivity of F-SSRT specimens with square wave loading is weak, and the fracture is straight; the SCC sensitivity of F-SSRT specimens with superimposed triangular wave loading is in the middle, and the fracture edge is serrated; The F-SSRT specimens with superimposed sine wave loading own the strongest SCC sensitivity, and the fracture is an oblique section fracture extending along the 45° direction. Different superimposed loads with different waveforms result in different SCC test results including different fracture morphology and change rules, which are caused by the change of the direction and magnitude of the applied force of the superimposed load, not only attributing to the different superimposed load energy.

Effect of cathodic polarization on stress corrosion cracking susceptibility of 35CrMo steel for Class 12.9 fasteners in seawater

The effect of cathodic polarization on stress corrosion cracking (SCC) of 35CrMo steel for high strength fasteners in seawater was investigated by electrochemical measurement, slow strain rate tensile tests and fracture analyses. The results demonstrated that the 35CrMo steel with a typical tempered martensite microstructure has some SCC susceptibility at the open circuit potential (OCP), and the susceptibility decreases as the potential is shifted negatively until −850 mV vs. SCE, at which the steel presents the lowest SCC susceptibility due to the inhibition of anodic dissolution (AD) and little hydrogen evolution. The SCC sensitivity increases significantly as the applied potential further shifts negatively because of intensive hydrogen evolution. The fractures are transgranular at all potentials. AD is considered to be the main cracking mechanism at OCP, while hydrogen embrittlement becomes dominant at the potential below −850 mV vs. SCE.

Stress corrosion cracking of X80 steel heat-affected zone in a near-neutral pH solution containing Bacillus cereus

Bacillus cereus (B. cereus) is observed to have varying effects on the stress corrosion cracking (SCC) sensitivity of different microstructures in the simulated heat-affected zone (HAZ) of X80 steel. At open circuit potential (OCP), the SCC sensitivity of different microstructures increased from 3.40–7.49% in an abiotic medium to 10.22–15.17% in a biotic medium. At −0.9 V (SCE), it increased from 22.81–26.51% to 35.76–39.60%. The increment in SCC sensitivity upon exposure to B. cereus was highest in the coarse-grained HAZ (7.68 and 16.79% at OCP and −0.9 V, respectively), followed by the intercritical and fine-grained HAZs. Owing to differences in the phase composition, grain boundary type, dislocation density, and surface volta potential, the initial adhesion number and position of B. cereus in the microstructure of the HAZ were differed, resulting in different sensitivities to SCC.

Stress corrosion cracking of 316LN stainless steel with orthogonal scratches

316LN stainless steel is used to produce the third generation primary circuit pipe of pressurized water reactor (PWR). Its internal and external pipe surfaces are generally introduced with scratches when manufactured, transported and installed processes, making their research and discovery on the stress corrosion cracking (SCC) sensitivity challenging. In the present study, multiple orthogonal scratches on 316LN stainless steel are prepared using the rotary cutting head. The effects of the orthogonal scratches on the SCC of 316LN stainless steel are investigated. The experimental results show that the force bearing point of this kind of rotary cutter head is near 60° on the side, which is different from the common cutter head. At the intersection of orthogonal scratches, larger strain concentration and more oxide particles can be formed comparing with single scratch. With increasing strain concentration, the more nucleation sites and the greater growth driving force for the oxide particles can be formed. Thus larger and more oxide particles in this case are generated, resulting in finally a greater SCC sensitivity.

Experimental investigation of stress corrosion on supercritical CO2 transportation pipelines against leakage for CCUS applications

Carbon Capture, Utilization and Storage (CCUS) is one of the key technologies that will determine how humans address global climate change. For captured CO2, in order to avoid the complications associated with two-phase flow, most carbon steel pipelines are operated in the supercritical state on a large scale. A pipeline has clear Stress Corrosion Cracking (SCC) sensitivity under the action of stress and corrosion medium, which will generally cause serious consequences. In this study, X70 steel was selected to simulate an environment in the process of supercritical CO2 transportation by using high-temperature high-pressure Slow Strain Rate Tensile (SSRT) tests and high-temperature high-pressure electrochemical test devices, with different O2 and SO2 contents. Studies have shown that 200 ppm SO2 shows a clear SCC sensitivity tendency, which is obvious when the SO2 content reaches 600 ppm. The SCC sensitivity increases with the increase of SO2 concentration, but the increase amplitude decreases. With the help of advanced microscopic characterization techniques such as scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), through the analysis of fracture and side morphology, the stress corrosion mechanism of a supercritical CO2 pipeline containing SO2 and O2 impurities was obtained by hydrogen embrittlement fracture characteristics. With the increase of SO2 content, the content of Fe element decreases and the corrosion increases, demonstrating that SO2 plays a leading role in electrochemical corrosion. This study further strengthens the theoretical basis of stress corrosion of supercritical CO2 pipelines, plays an important role in preventing leakage of supercritical CO2 pipelines, and will provide guidance for the industrial application of CCUS.

Effects of Multi-Pass Turning on Stress Corrosion Cracking of AISI 304 Austenitic Stainless Steel

Austenitic stainless steels are extensively used in mechanical engineering. The machined surface integrity has an essential influence on the stress corrosion cracking (SCC) performance of stainless steels. In this paper, the effects of multi-pass turning on the SCC susceptibility of AISI 304 austenitic stainless steel were investigated by correlating the SCC crack density to the machining-induced surface characteristics in terms of roughness, micro-hardness, and residual stress. In the multi-pass turning, the surface roughness and residual stress were the least after the double pass turning, and the surface micro-hardness was the maximum after the triple-pass turning. The SCC susceptibility was evaluated after SCC tests in boiling MgCl2 solution. The results showed that the weakest SCC sensitivity was observed in double-pass turning 304 stainless steel, while the most susceptible SCC was found in triple-pass turning. Compared with the double-pass turning, the increase in SCC sensitivity of triple-pass turning was attributed to the larger roughness, higher micro-hardness and greater residual tensile stresses.

Influence of anion and sulfate-reducing bacteria on the stress corrosion behavior and mechanism of X70 steel in a marine mud environment

Subsea pipeline steel was severely corroded due to the presence of huge quantities of Cl-, SO42-, and sulfate-reducing bacteria (SRB) in marine mud. In this paper, the synergistic effects of Cl-, SO42- and SRB on the stress corrosion cracking (SCC) behavior of X70 steel in a simulated solution of marine mud in the South China Sea were examined using slow strain rate tensile (SSRT) tests, surface morphology analysis, and combined electrochemical experiments. The results indicated that the sensitivity of the specimens to stress corrosion increased as the concentration of Cl- rose. Cl- not only encouraged pitting and intensified the corrosion autocatalytic process but also influenced the number of surviving SRB. At a concentration of 20 g/L, the greatest number of SRB survived in the present investigation. However, when the Cl- concentration was 30 g/L, the anodic dissolution rate was the quickest and the SCC sensitivity was the highest, due to the synergistic impact of the high Cl- concentration and SRB. SO42- functions as an electron acceptor for SRB in the electrochemical reaction process and influences the adsorption of Cl-. Its rising concentration sped up the anodic dissolving process and increased the sensitivity of SCC.

Effect of Overlaying Welding Repair on Stress Corrosion Cracking Sensitivity of Low-Pressure Nuclear Steam Turbine Rotor in the Simulated Environment

Effect of Overlaying Welding Repair on Stress Corrosion Cracking Sensitivity of Low-Pressure Nuclear Steam Turbine Rotor in the Simulated Environment

Mechanical properties and stress corrosion cracking behavior of a novel Mg-6Zn-1Y-0.5Cu-0.5Zr alloy

The strengthening mechanism and stress corrosion cracking (SCC) behavior of a new Mg-6Zn-1Y-0.5Cu-0.5Zr alloy (given the name “ZWCK6100″) were investigated in this work. The results showed that the microstructure, mechanical properties and stress corrosion resistance were significantly affected by the combined addition of Cu and Y. The alloy consisted of α-Mg, Zn2Zr, CuMgZn, rod-shaped MgZn2 precipitates and I phase (Mg3Zn6Y), and displayed a balance between strength and ductility, with the yield strength, ultimate tensile strength and elongation being 320.3 MPa, 351.5 MPa and 19.8%, respectively. The main strengthening mechanisms were found to be grain refinement, second phases and texture. In addition, the stress corrosion resistance was assessed by slow strain rate testing and fractography. These tests showed that ZWCK6100 alloy exhibited improved SCC resistance and low SCC sensitivity in 3.5 wt% NaCl solution. The novel ZWCK6100 alloy may serve as a promising magnesium alloy for industrial applications.

Welding heat input for synergistic improvement in toughness and stress corrosion resistance of X65 pipeline steel with pre-strain

The microstructure, hydrogen embrittlement sensitivity, fracture toughness, and influence of pre-strain on the sulfide stress corrosion cracking (SSCC) sensitivity of the coarse-grained heat-affected zone of X65 pipeline steel with large deformation were studied to determine the optimal welding heat input in an acidic H2S environment. After pre-straining, the microstructures of the specimens changed insignificantly, but their ductility decreased. The acicular ferrite microstructure obtained under a low heat input demonstrated the synergistic improvement in the SSCC resistance and fracture toughness under pre-strain, especially at t8/5 = 20 s. The M/A constituents interface potentially causes microcrack initiation and interconnection under pre-strain.

Microstructural Effects in the Development of Near-Neutral pH Stress Corrosion Cracks in Pipelines.

The corrosion and stress corrosion cracking (SCC) behaviors of 20#, X60, and X80 pipeline steels in a near-neutral pH environment were investigated by means of electrochemical measurement, immersion test, and interrupted slow strain rate tensile (SSRT) test. The propensity for SCC, as indicated by the stress threshold value for crack initiation, was found to be dependent on the type of steel microstructure. Cracks were initiated in the high-strength steel X80 at a stress less than its yield strength, whereas in the other lower-grade steels, the initiation of cracks occurred after the yielding point. The threshold stress of SCC initiation in the near-neutral pH environment for 20#, X60, and X80 steels were 130.64% σys, 106.79% σys, and 86.92% σys, respectively. The SCC of 20# and X60 were characterized by the formation of transgranular and intergranular cracks, while X80 steel was only by transgranular cracking. The occurrence of corrosion had a great effect on crack initiation and the growth at the later stage. The latter involved hydrogen effects. A correlation between SCC sensitivity and the yield strength of the steel has been identified.