Susceptibility Of Stainless Steels Research Articles

Influence Mechanism of Solidification Mode on Solidification Cracking Susceptibility of Stainless Steels

Influence Mechanism of Solidification Mode on Solidification Cracking Susceptibility of Stainless Steels

Alumina lath-like structure-rGO–PVDF hybrid film formation with high-performance corrosion protection for 316L stainless-steel alloy

The susceptibility of stainless steel (SS) to corrosion can necessitate the use of an effective surface coating for application in various industries. In this study, the lath-like structure of aluminium oxide (Al2O3) has been successfully synthesized via a sol–gel process using the ionic liquid, 1-hexyl-3-methylimidazolium hexafluorophosphate. The uniform alumina lath-like structures with a diameter of 105 ± 22 nm and length of 340 ± 66 nm were characterized with various techniques, including X-ray diffraction (XRD), transmission electron microscope (TEM), field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS). Furthermore, the alumina nanoparticles were functionalized with a silane compound. Composite of reduced graphene oxide (rGO), functionalized Al2O3, and polyvinylidene fluoride (rGO/Al2O3–PVDF) with Al2O3 concentration of 1 wt.% was successfully prepared. The composites were then characterized and utilized for SS protection in a saline solution (3.5% NaCl). Excellent corrosion resistance was conferred to the SS surface using the rGO/Al2O3–PVDF coating with 1% Al2O3 (rGO/Al2O3–1.0–PVDF), which outperformed the other coatings, as indicated by electrochemical characterization using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). The water contact angle of rGO/Al2O3–1.0–PVDF-coated SS was 142.5°, demonstrating good hydrophobicity. The protection mechanism was clarified using both electrochemical and surface characterizations. The remarkable protection performance of rGO/Al2O3–1.0–PVDF is related to the control of charge transfer at the SS/electrolyte interface, which prevents alloy dissolution. Furthermore, the presence of Al2O3 passivates any graphene defects that may be present, which further reduces the corrosion rate, thus providing enhanced protection compared to the rGO/PVDF and neat PVDF coatings.

Thickness-dependent pitting corrosion behavior in Ni–Nb thin film metallic glass

Thin film metallic glasses (TFMGs) with a composition of Ni60Nb40 were magnetron sputtered on the substrate of austenitic stainless steel (SS). Potentiodynamic polarization measurements on TFMGs with different thicknesses in NaCl solution were conducted, and better corrosion resistance is achievable by increasing the film thickness. However, a critical film thickness exists, above which anti-pitting property cannot be significantly improved. The film density as a function of thickness has a similar tendency with the corrosion resistance, indicating the correlation of film density and corrosion resistance. Fossettes in the pits were observed in TFMGs deposited on SS rather than the bare SS, since pitting nuclei in TFMG can propagate more rapidly along depth than width due to the stronger pitting susceptibility of SS.

Steel Contamination of Biomedical Titanium Alloys during Hot Isostatic Pressing Treatments

Hot isostatic pressing (HIP) is an industrial treatment for the consolidation of metallic components. In the biomedical field, HIP processes are applied to titanium alloys fabricated by other sintering techniques to reduce residual porosity and improve the mechanical characteristics. Stainless steel sheet encased HIP processes are used when surface open porosities are present, in particular for powder metallurgy products or when nitrogen absorption is a major concern. In these circumstances, localized steel contamination may occur on the titanium surface. Contamination could be easily avoided using titanium encasing sheets, but these are rarely applied in industrial practice. In this work, Grade 2 and Grade 5 titanium have been treated with a standard HIP process. During treatment both alloys have been kept in contact with stainless steel casement, causing diffusion of elements inside the titanium. Samples have been investigated using two-dimensional profilometry and scanning electron microscopy. Qualitative and semi-quantitative compositional analyses have been performed using energy-dispersive x-ray spectroscopy and glow discharge optical emission spectrometry (GDOES). Microstructural analyses have been obtained after GDOES plasma etching in order to avoid any further surface preparation and easily obtain comparable results from the two different alloys. Localized potentiodynamic polarization curves were obtained on the different regions of the samples using microcell equipment. Both alloys were contaminated by stainless steel elements in the stained regions. A reduction in the corrosion resistance of the alloys has been observed due to the contamination. The experimental setting demonstrated the corrosion susceptibility of stainless steel contaminated biomedical titanium alloys after HIP, even if the passive behavior of titanium was not completely compromised.

IGSCC of Non-Sensitised Austenitic Stainless Steels in BWR Environment – Effect of Deformation Mode on Grain Boundary Susceptibility

Intergranular Stress Corrosion Cracking (IGSCC) of austenitic Stainless Steels (SS) in Boiling Water Reactor (BWR) environment is generic in nature in both the sensitised and the non-sensitized conditions. IGSCC in non-sensitized austenitic SS in the strain hardened condition has been reported without any grain boundary chromium depletion or impurity segregation. The present study ascertains the reason for IGSCC in BWR environment in non-sensitized condition and investigates the effect of nitrogen content in SS on the susceptibility to IGSCC. Two heats of type 304LN stainless steel with 0.08 and 0.16 wt. % nitrogen were used. Strain hardening was done by cross rolling at 200 °C to 20 % thickness reduction (warm rolling) to simulate the weld induced strain in constrained welds. Subsequently, Transmission Electron Microscopic (TEM) examination was carried out on the rolled SS. The deformation mode observed due to warm rolling was predominantly elongated twin and shear band (SB) formation in both the SS, terminating at the grain boundary regions. This resulted in higher stresses and strains making grain boundary susceptible to IGSCC. Presence of more dislocations at grain boundaries is a key feature for such enhancement in the susceptibility of non-sensitized SS to IGSCC. Formation of twins and SB occurred to a greater extent in the SS with higher nitrogen content indicating greater susceptibility to IGSCC in BWR environment. Crack growth studies done in simulated BWR environment at different Dissolved Oxygen (DO) levels showed higher crack growth rates in the SS with higher nitrogen content in the non-sensitised and strain hardened condition, confirming the higher susceptibility of SS with a higher level of nitrogen.

Fluxmeter for Measuring the Magnetic Susceptibility of Stainless Steel Samples

A portable device for measuring very low levels of the magnetic susceptibility of stainless steel is described. Taking into account that the magnetic susceptibility of stainless steel decreases with an increasing external magnetic field, the detector of the device is supplied with a small-size magnet producing a magnetic field of about 0.15 T at the measurement point. The device sensitivity χ is 0.001.

Application of electrochemical methods to the investigation of corrosion fatigue of metals

Using electrochemical methods, we investigate a process of corrosion fatigue fracture of stainless steels of various classes and LS59-1 brass in chloride-containing media. We establish the correlation between a change in electrochemical parameters in the process of corrosion fatigue and stages of fracture of specimens. We estimate the deformation activation of metals and its influence on the intensity of accumulation of corrosion fatigue damages, formation of pittings, and components of impedance. We show that cyclic stresses have different effects on dissolution of separate components of alloys, the intensity of which depends on the limiting stage of the electrode process (the diffusion stage or the electrochemical one). On the basis of the investigations performed, we conclude that the susceptibility of stainless steels to corrosion fatigue is determined by the efficiency of local activation and repassivation.

Application of the Modified Electrochemical Potentiodynamic Reactivation Method to Evaluate Intergranular Corrosion Susceptibility of Stainless Steels

Abstract A new activator was proposed to evaluate the susceptibility of type 304L (UNS S30403) stainless steel (SS) to intergranular corrosion (IGC) using the electrochemical potentiodynamic reactivation (EPR) technique. Thioacetamide (CH3CSNH2) was proven to be more suitable as an activator than other compounds containing sulfur. Use of the modified EPR test with the new activator was investigated on types 304L SS and 308L SS (UNS S30800) and on weld buildup type 308L SS. Results showed the modified EPR test differentiated the degree of sensitization (DOS) of steel mildly, slightly, or entirely free of sensitization. DOS of type 304L SS sensitized at 650°C for various time periods as determined by the modified EPR test with CH3CSNH2 was compared to the traditional EPR test with potassium thiocyanate (KSCN) as the activator and to the copper-accelerated Strauss test. The modified EPR test was more sensitive to detect sensitization than the traditional EPR test and was more capable of detecting and quantif...

The pitting susceptibility of stainless steels after a stay at open circuit in acidified chloride containing solution

In acidic chloride-containing solution, the passive film formed at open circuit becomes unstable over a certain period, as revealed by subsequent potentiostatic electrochemical noise measurements, showing specific current peaks. A hypothesis is made about the possible influence of a salt layer forming on pit walls during both the propagation and repassivation of unstable pits.

Cracking susceptibility of stainless steel subjected to plasma disruption

Cracking susceptibility of stainless steel subjected to plasma disruption

EM study of carbon content effects on carbide precipitation and chromium depletion in type 304 stainless steels

Carbon content is the most critical compositional variable in carbide precipitation and sensitization development in stainless steels (SS). Quantitative electrochemical test methods have conclusively demonstrated that an increase in carbon content enhances the susceptibility of SS to sensitization development. The increase in sensitization has been considered to be caused by the influence of carbon on the thermodynamics of the precipitation-depletion process. This has been supported by limited TEM work. In this research, we are using electron microscopy to quantify the effects of carbon content on carbide precipitation and chromium-depletion development in SS. Initial observations that compare precipitation characteristics and depletion profiles in 0.011% C, 0.025% C, 0.051% C, and 0.07% C-containing, 304 SS heat treated at 775°C for 0.1-500 h are presented in this paper, and will be enhanced by a statistical analysis of carbon content effects on precipitate sizes, densities, and depletion profiles, to provide a valuable insight into the precipitation-depletion phenomena.

Importance of microstructure in determining environmental susceptibility of stainless steels

Weight loss and stress corrosion studies on ASTM A304 stainless steels subjected to different degrees of cold working and exposed to magnesium chloride solutions at different pH levels revealed that environmental resistance is a sensitive function of microstructure. Slip bands are preferential regions of attack in cold worked structures, while sensitization alters the crack path to follow the grain boundaries. The similarities in the relative susceptibility of the various microstructural features under conditions of general corrosion, stress corrosion, and hydrogen embrittlement suggests that any mechanism that is developed must be able to comprehensively explain the observed phenomena under all three forms of environmental degradation.

ステンレス鋼の鋭敏化とBWR模擬環境中における粒界応力腐食割れ感受性との関係

ステンレス鋼の鋭敏化とBWR模擬環境中における粒界応力腐食割れ感受性との関係

Crevice Corrosion of Stainless Steels and Nickel Alloys under Marine Conditions

The susceptibility of stainless steels and high nickel alloys to crevice corrosion severely restricts their use for marine engineering applications. The development of crevice corrosion test procedures for alloy evaluation and development purposes is reviewed. As susceptibility to crevice corrosion is an inherent weakness of this type of alloy, it is suggested that it might in future be more rewarding to determine the design parameters required for the prevention of crevice corrosion by galvanic protection, rather than to pursue the continuing present investment in the quest for the development of an immune alloy.

The Application of Electrochemical Techniques to the Study of Corrosion of Automotive Trim Materials

Abstract De-icing salts are known to have a contributing effect on the corrosion of automotive trim materials. Various accelerated tests have been developed to evaluate the corrosion resistance of trim materials, but each test has its own limitations. Electrochemical techniques are a valuable supplement to these other methods, not only because they are fast and reproducible but also because they help in determining mechanisms of reactions. A potentiodynamic anodic polarization method was used to show the relative corrosion resistance of four different stainless steels and a chromium plated stainless steel used in trim applications, and the order of corrosion resistance compared favorably with that obtained by conventional chemical tests and by field exposure. Furthermore, the test was used to show distinct differences in the pitting susceptibility of stainless steels exposed to different concentrations of chloride ion. The thermographic test is commonly used to evaluate the corrosion resistance of stainless steels. The effect of specific ingredients in the solution on corrosion was determined by both chemical and electrochemical tests. Chemical tests showed that chloride and thiosulfate ions had the greatest effect on pit initiation, probably because the thiosulfate altered the redox potential of the solution. Potentiodynamic polarization measurements indicated that the chloride ion concentration was rate controlling after corrosion had begun, and the thiosulfate ion caused a shift in potential which placed the material in a corroding region.