Good Stress Corrosion Cracking Resistance Research Articles

Effect of Organizational Evolution on the Stress Corrosion Cracking of the Cr-Co-Ni-Mo Series of Ultra-High Strength Stainless Steel.

Different microstructures were obtained under various thermal conditions by adjusting the heat treatment parameters of the Cr-Co-Ni-Mo series of ultra-high strength stainless steel. The effect of organizational evolution on the stress corrosion cracking (SCC) of the Cr-Co-Ni-Mo series of ultra-high strength stainless steel was investigated using potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and other test methods in combination with slow strain rate tensile tests (SSRTs). The results show that the Mo- and Cr-rich clusters and precipitation of the Laves phase reduce the corrosion resistance, while increasing the austenite content can improve the corrosion resistance. The Cr-Co-Ni-Mo series of ultra-high strength stainless steel has a high SCC resistance after quenching at 1080 °C and undergoing deep cooling (DC) treatment at −73 °C. With increasing holding time, the strength of the underaged and peak-aged specimens increases, but the passivation and SCC resistance decreases. At the overaged temperature, the specimen has good SCC resistance after a short holding time, which is attributed to its higher austenite content and lower dislocation density. As a stable hydrogen trap in steel, austenite effectively improves the SCC resistance of steel. However, under the coupled action of hydrogen and stress, martensitic transformation occurs due to the decrease in the lamination energy of austenite, and the weak martensitic interface becomes the preferred location for crack initiation and propagation.

Corrosion Behavior of P110S Oil Pipe in Simulated Working Condition

The corrosion resistance of P110S steel in CO2 and H2S coexistence corrosion environment under different temperature and PCO2/PH2S was investigated by high temperature and high pressure (HTHP) reaction kettle combined with SEM, EDS and XRD analysis methods. The stress corrosion cracking (SCC) resistance of P110S steel was studied under loading pressure of 682.2MPa (758MPa×90%) in simulated conditions after 720 hours test. The results show that the P110S steel has serious corrosion in the range of simulative temperature and H2S partial pressure. With the increase of temperature, the corrosion rate decreases first and then increases. With the increase of H2S partial pressure, the corrosion rate increases first and then decreases. The P110S steel has the highest corrosion rate when the temperature is 50 °C and H2S partial pressure is 0.1%. After the anti-SCC test, the specimens did not fracture, and cracks perpendicular to the tensile stress were not found on the surface. That is, P110S has good SCC resistance in the corrosive environment.

Effect of Cold Rolling on the Transformation Kinetics of Sigma- and Chi- Phases in UNS S32205 Duplex Stainless Steel

Abstract Duplex stainless steels have very good properties including good ductility, moderate toughness and good stress corrosion cracking resistance. These properties can be severely affected by the precipitation of sigma (σ) and chi (χ) phases, in particular ductility and toughness. The effect of cold deformation on the isothermal transformation kinetics of UNS S32205 steel was investigated. The steel was cold rolled up to 64 % reduction in thickness and annealed at 850 °C from 10 min up to 4320 min (3 days). Microstructural characterization used light optical and scanning electron microscopy, energy dispersive spectroscopy, and magnetic measurements. Formation of intermetallics is much faster in the cold-rolled samples. After 4320 min, samples show the same amounts of each phase for all rolling strains. Results have been validated by thermodynamic calculations.

The Influence of Multiple Welding Repairs of Pipelines in Residual Stress Assessment Related to Stress Corrosion Cracking

The effect of residual stress of multiple welding repairs in seamless API 5L X52 on the stress corrosion cracking (SCC) susceptibility was evaluated. Four repairs of the girth weld were evaluated through X-ray diffraction (XRD) on the internal face of the pipe to measure residual stresses in longitudinal and circumferential direction. Residual stresses in the circumferential and longitudinal direction reach values of about 77% and 58% of the UTS (460 MPa) respectively, approaching to the YS of the steel (360 MPa). It was observed that its magnitude increases as move away from weld center line. SCC susceptibility of X52 steel welded joints with the residual Original Research Article Contreras et al.; BJAST, 6(6): 621-634, 2015; Article no.BJAST.2015.117 622 stresses generated was evaluated through slow strain rate tests (SSRT) in a soil solution at low and high pH. Relation between mechanical properties and residual stresses on the SCC susceptibility was analyzed. SCC index obtained from the mechanical properties of SSRT indicate good SCC resistance of X52 steel exposed to soil solution at low and high pH. From these results, it is suggested that the region with high residual stresses before to generate cracks in the steel surface due to the combination of soil solution and the strain applied, should favor pitting formation and not cracking. Initiation of micro-cracks from these pits will depend on the geometrical form of the pit and the stresses state can be established at given pitting. It is suggested that initiation of micro-cracks from these pits may depend on the dissolution rate and morphology of the pitting and stresses on the bottom of the pitting. This favorable condition could appear increasing the soil exposition time of the steel and reducing the strain rate applied on the SSRT.

The Role of Residual Stresses in Circumferential Welding Repairs of Pipelines in SCC Susceptibility

The main objective of the present study is to measure the residual stresses in the circumferential welding joints of X52 pipeline steel with multiple welding repairs, and then relate these residual stresses to study the influence on the high pH stress corrosion cracking (SCC) susceptibility. Four conditions of shielded metal arc welding (SMAW) repairs of the girth weld were evaluated. The residual stresses were measured through X-ray diffraction (XRD) on the internal side of the pipe in longitudinal and circumferential direction. Residual stresses in the circumferential and longitudinal direction reach values of about 98 and 74% of the yielding strength (360 MPa) respectively. The effect of residuals stresses in the high pH-SCC susceptibility of X52 pipeline steel was evaluated through slow strain rate tests (SSRT) in a simulated soil solution. Relation between SCC index and residual stresses on the SCC susceptibility was analyzed. Results of SCC index taking account the ratios obtained from the mechanical properties of the welding joints evaluate (containing different levels of residual stresses) showed good SCC resistance. It was observed that increasing the magnitude of residual stresses, the SCC susceptibility increases. For all the SSRT specimens the failure occurs in the base metal and heat affected zone (HAZ) interface.

Residual Stress Assessment and its Effect on SCC of Pipelines Steel in Acidic Soil Environment

ABSTRACTEffect of residual stresses of multiple welding repairs on API 5L X52 pipeline steel on stress corrosion cracking (SCC) in a simulated acidic soil solution was studied. Four conditions of repairs of the girth weld were evaluated. The residual stresses were measured through X-ray diffraction (XRD) on the internal side of the pipe in longitudinal and circumferential direction. The circumferential and longitudinal residual stresses values are compressive on the inner surface of the welding joints. The highest residual stresses were measured in the hoop direction reaching values of about 98% of the yielding strength (360 MPa). It was observed that its magnitude increases as move away from weld center line. The effect of residuals stresses in the SCC susceptibility of X52 pipeline steel was evaluated through slow strain rate tests (SSRT) in a simulated acidic soil solution. Relation between mechanical properties obtained from SSRT and residual stresses on the SCC susceptibility was analyzed. Results of SCC index taking account the ratios obtained from the mechanical properties of the welding joints evaluate, showed good SCC resistance in acidic soil solution at low pH. Scanning electron microscopy (SEM) observations showed that the region with high residual stresses prior to generate cracks in the steel due to the combination of soil solution and the strain exerted, should favor pitting formation and not cracking.

Effect of Temperature and Chloride Content on the Stress Corrosion Cracking Susceptibility of 304 Stainless Steel Welded Joints Treated by Ultrasonic Impact Treatment

Effect of temperature and chloride content on the stress corrosion cracking (SCC) susceptibility of 304 stainless steel welded joints treated by ultrasonic impact treatment (UIT) is investigated in this study. High tensile weld residual stress is an important factor contributing to SCC. UIT can produce compressive stresses on the surface of welded joints that negate the tensile stresses to enhance the SCC resistance of welded joints. In the SCC testing, the specimens were immersed in sodium chloride solution at the temperatures of 200 °C–280 °C in the range of sodium chloride solution from 50 g/L to 200 g/L. During the testing, treated specimens show good SCC resistance with different temperature and consistency of chloride ion. The results show that the SCC susceptibility of 304 stainless steel welded joints reduces with increase of temperature and decrease of chloride ion consistency. The surface roughness of sample after UIT was investigated by portable surface roughness tester. The results reveal that surface of the samples becomes rougher than the original plate with the increase of the impact duration, which contribute to the pitting corrosion of treated specimens. And, the level of pitting corrosion is reduced with increase of temperature.

A Ni- and Cu-free Zr-based bulk metallic glass with excellent resistance to stress corrosion cracking in simulated body fluids

Abstract In order to evaluate stress corrosion cracking (SCC) susceptibility of a Ni- and Cu-free Zr 56 Al 16 Co 28 bulk metallic glass (BMG) for biomedical application, the SCC behaviour of the BMG in various simulated body fluids (SBFs) including Hanks’, PBS(−) and 0.9% NaCl solutions open to air at 37 °C has been investigated using a slow strain rate technique (SSRT) at various initial tensile strain rates in the region of 5 × 10 −7 to 5 × 10 −4 s −1 . It was found that the Zr–Al–Co BMG exhibited excellent resistance to SCC in all of tested conditions. The amounts of cytotoxic cobalt ions released from the BMG disks of 5 mm in diameter were lower than those from the currently used biomaterial Co–Cr–Mo alloy. XPS analysis revealed that zirconium and aluminium ions were enriched in both air-formed and passive films. Moreover, these films were composed of double oxyhydroxide of zirconium, aluminium and cobalt. The formation of the stable and homogeneous double oxyhydroxide film enriched with zirconium and aluminium cations seems to be responsible for the high corrosion resistance and hence good SCC resistance of the Zr–Al–Co glassy alloy in SBFs. Thus, the Zr 56 Al 16 Co 28 BMG can be potentially promising material for biomedical applications.

Microalloying of Sc, Ni, and Ce in an advanced Al-Zn-Mg-Cu alloy

Using transmission electron microscopy (TEM), scanning electron microscopy, X-ray diffraction (XRD), and optical microscopy, the effects of microalloying elements of Sc, Ni, and Ce on the microstructure of a new super-high-strength ingot metallurgy (IM)/Al-Zn-Mg-Cu alloy (C912) have been correlated with mechanical properties and stress corrosion cracking (SCC) behavior. Using microalloying with Sc, Ni, and Ce, the C912 alloy can exhibit very high strength and good SCC resistance. Compared to the baseline C912 alloy, Sc refines the microstructure and retards recrystallization, Ni promotes the development of matrix precipitates, which enhance the strength and SCC resistance, and Ce has little effect on alloy strengthening in the three microalloying additions studied. The Sc-containing alloy (C912S) is the most attractive and even exhibits higher strength (ultimate tensile strength (UTS) greather than 660MPa) than the new Alcoa aluminum alloy 7055 and the Russian alloy B96, which have the highest strengths of the commercial IM/Al-Zn-Mg-Cu alloys.

Ａｌ‐Ｚｎ‐Ｍｇ‐Ｃｕ‐Ｌａ系押出合金の引張強度特性と耐応力腐食割れ性に及ぼすＣｒ，ＭｎおよびＭｇ添加の影響

Two groups of the extruded high strength Al-Zn-Mg-Cu-La system alloys, including Al-10 wt.%Zn-1 wt.%Mg-1.5 wt.%Cu-3 wt.%La with various Cr and Mn contents and Al-8 wt.%Zn-1.2 wt.%Cu-4.0 wt.%La with various Mg contents, were developed as the mechanical materials with a good stress corrosion cracking (SCC) resistance. In these alloys, the effects of the additional elements were investigated on the mechanical properties and SCC life. The main results are as follows;(1) The second phase particles which contained Zn and La were observed in the matrix, and dispersed homogeneously. The size of the particles was 5 to 10μm. For the alloys with Cr, dispersoids including Cr were also observed in the matrix. Their size was over 10μm.(2) The maximum value of 568MPa in tensile strength was observed in Al-8 wt.%Zn-1.2 wt.%Cu-4.0 wt.%La with 2.5 wt.%Mg, which was nearly equal to the commercial aluminum alloys7075-T73 and 7475-T6.(3) The excellent resistance of SCC was obtained in these alloys. Their SCC lives were over 15 times as long as that of Al-8 wt.%Zn-1 wt.%Mg master alloy. In conclusion, we developed extruded Al-high Zn-low Mg system alloys with high strength and good SCC resistance.

応力腐食割れ特性に優れた高力Ａｌ‐Ｚｎ‐Ｍｇ‐Ｌａ系合金の開発とその評価 （第４報） 耐応力腐食割れ性に優れた高力Ａｌ‐Ｚｎ‐Ｍｇ‐Ｃｕ‐Ｌａ系押出合金の破壊じん性と第二相粒子の関係

Extruded Al-8wt.% Zn-1-2.5wt.% Mg-1.2wt.% Cu-4wt.% La alloys with high tensile strength and good stress corrosion cracking resistance were developed and their fracture toughness was investigated. The effect of metallurgical parameter on the fracture toughness value was examined. The main results are as follows;(1) The fracture toughness values of the extruded Al-8wt.% Zn-1-2.5wt.% Mg-1.2wt.% Cu-4wt.% La, which were about 20MPa√m without anisotropy, were not influenced by Mg content.(2) The second phase particles in the extruded alloys, which consisted of Zn and La, were estimated quantitatively. The mean diameter was about 4.7μm and the volume fraction of the particles was 1.6-2.3vol.%.(3) The second phase particles consisting of Zn and La in the extruded alloys cracked easily, and became the nucleus of voids when the matrix fractured. The fracture toughness of the extruded alloys was affected by the particles. The fracture toughness value, KIc, was related to the volume fraction of the second phase particles, fv, and the mean diameter of the particles, D, as follows:KIc≈[ζσ0.2E(π/6)1/3D]1/2·fv-1/6∝(DEσ0.2)1/2·fv-1/6where ζ is constant, σ0.2 is 0.2% proof stress and E is Young's modulus.

SCC Behavior of an Al-3.7wt%Zn-2.5wt%Mg Alloy Before and After Welding in 3.5% NaCl Solution

Abstract The behavior of stress corrosion cracking (SCC) of an overaged Al-3.7wt%Zn-2.5wt%Mg alloy including base metal, weldment, and heat-affected zone (HAZ) in 3.5% NaCl solution was investigated. This Al-Zn-Mg alloy loaded in longitudinal or long transverse direction has good SCC resistance and is maintained even after welding. Welding residual stress alone does not induce the SCC of the weldment. The result of the specially modified type I double cantilever beam (DCB) testing shows that the crack can be arrested by the weld metal because of the better SCC resistance of the filler metal ER5183. In addition, a specially designed type II DCB testing indicates that the SCC resistance of the HAZ is better than that of the base metal because of the re-overaging of the HAZ during welding.

Evaluation of the resistance of irradiated zirconium-liner cladding to iodine-induced stress corrosion cracking

An evaluation was made of irradiated zirconium-liner cladding for its resistance to iodine-induced stress corrosion cracking (SCC). Emphasis was put on irradiation-induced hardening in zirconium and SCC resistance in zirconium-liner cladding as compared with Zircaloy-2 cladding. The Vickers microhardness test revealed that crystal bar zirconium experienced less hardening than Zircaloy-2 during neutron exposure. The SCC resistance of zirconium-liner cladding was evaluated for failure strains under the tube pressurization SCC test, and compared with the results of Zircaloy-2 cladding. The failure strains of zirconium-liner cladding were significantly larger than those of Zircaloy-2 cladding over all neutron fluence ranges examined, e.g., more than ten times at 1.0 × 10 21 n/ cm 2 ( E > 1 MeV). Judging from our results on the Vickers microhardness and SCC tests, good SCC resistance of zirconium-liner cladding could be expected even at high fluences.