Corrosion Study of Base Material and Welds of a Ni–Cr–Mo–W Alloy

Mishra, Ajit

doi:10.1007/s40195-017-0559-6

Cited by 12 publications

(4 citation statements)

References 17 publications

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“…According to the fitting parameters, n is a measure of the capacitance dispersion with values between 1 (ideal capacitance) and 0.7 (highly dispersed capacitance). The NiCr x Mo 0.1 coating with middle Mo content showed a better corrosion resistance than the other coatings, and the increase in the Cr content had a positive effect on the corrosion resistance of the NiCr x Mo y coatings [44]. The EIS results are consistent with the potentiodynamic polarization curve trend.…”

Section: Electrochemical Impedance Spectroscopysupporting

confidence: 74%

Synthetic Effect of Cr and Mo Elements on Microstructure and Properties of Laser Cladding NiCrxMoy Alloy Coatings

Zhang

Wang

et al. 2020

Acta Metall. Sin. (Engl. Lett.)

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NiCr x Mo y (x = 1, 1.5; y = 0, 0.1, 0.3) alloy coatings were prepared on the Q235 substrate by laser cladding under the protection of argon. The phase composition, microstructure, corrosion behavior, and mechanical properties of the NiCr x Mo y alloy coatings were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electrochemical tests, X-ray photoelectron spectroscopy, microhardness, and nanoindentation tests. As the Cr content increased, the phase composition of the coatings changed from a single face-centered cubic (FCC) structure to a dual-phase structure coexisting with body-centered cubic (BCC) and FCC structures, while the addition of Mo promoted the precipitation of σ phase. The appearance of a homogeneous dual-phase structure and some amount of σ phase played a positive role in the corrosion resistance of NiCr x Mo y coatings. Cr 3+ ions and Mo 6+ ions in the passive film enhanced the stability of the coatings. The nanoindentation tests showed that the nanohardness (6.71 GPa) and elastic modulus (184.40 GPa) of BCC phase were higher than those of the FCC phase (5.19 GPa and 155.26 GPa, respectively). Overall, the BCC phase and σ phase improved the mechanical properties of the coatings.

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Section: Electrochemical Impedance Spectroscopysupporting

confidence: 74%

Synthetic Effect of Cr and Mo Elements on Microstructure and Properties of Laser Cladding NiCrxMoy Alloy Coatings

Zhang

Wang

et al. 2020

Acta Metall. Sin. (Engl. Lett.)

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“…Several corrosion inhibitors have been adsorbed on Monel, and among them green corrosion inhibitors like sodium diethyl dithiocarbamates having a lone pair of electrons on their two sulfur atoms show strong adsorption on Monel [8]. The effect of hydrochloric acid concentration on the corrosion rate of Monel was reported by Mishra [9]. The corrosion resistance of Monel alloy at 923 K has been examined and was correlated to the metallic Li in the molten electrolyte [10].…”

Section: Introductionmentioning

confidence: 99%

Corrosion Protection of Monel Alloy Coated with Graphene Quantum Dots Starts with a Surge

Bopp

Santhanam

2019

ChemEngineering

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There has been an active interest in protecting metals and alloys using graphene coating. The mechanism by which corrosion protection occurs has not been well understood as the couple involved are both good electron conductors. In this work, we demonstrate that Monel alloy coated with graphene quantum dots (GQD) changes the corrosion rate with a surge (increase) caused by the galvanic coupling of the two materials. This surge results in the protective layer formation on Monel to inhibit the corrosion. X-ray fluorescence spectrum of Monel (400) alloy showed the composition of it as Ni (67.05%) and Cu (29.42%). The Tafel experiments carried out in NaCl and Na2SO4 electrolytes showed an initial enhancement of the corrosion rate followed by a decrease upon successive polarizations. Monel coated with graphene oxide (an insulator) shows no initial enhancement of corrosion rate; the coated samples showed a lower corrosion rate in comparison to the uncoated samples. X-ray fluorescence, Fourier Transform spectroscopy (FTIR) and Raman imaging studies have been carried out for understanding this transformation. Distinct peaks due to Ni-O stretching and Ni-O-H bending vibration were observed in the FTIR spectrum.

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“…Cr promotes excellent corrosion resistance in oxidizing environments by the formation of a stable passive layer. [9][10][11] Likewise, Mo protects the alloy in reducing environments (e.g., electrolytes containing HCl, H 2 SO 4 , and H 3 PO 4 ) and supports repassivation during localized corrosion. [9][10][11][12] Unfortunately, the literature on the corrosion performance of Alloy 725 is somewhat limited.…”

mentioning

confidence: 99%

“…[9][10][11] Likewise, Mo protects the alloy in reducing environments (e.g., electrolytes containing HCl, H 2 SO 4 , and H 3 PO 4 ) and supports repassivation during localized corrosion. [9][10][11][12] Unfortunately, the literature on the corrosion performance of Alloy 725 is somewhat limited. 2,3,13,14 Nonetheless, since Alloy 725 and Alloy 625 (UNS N06625) (Table I) have a comparable Cr and Mo content, their corrosion resistances are considered similar.…”

mentioning

confidence: 99%

Detecting Intergranular Phases in UNS N07725: Part I. Adapting the Double-Loop Electrochemical Potentiokinetic Reactivation Test

Hazarabedian

Lison-Pick

Quadir

et al. 2021

J. Electrochem. Soc.

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Precipitation hardened nickel-based Alloy 725 (UNS N07725) has been proven susceptible to hydrogen embrittlement in oil and gas production. Moreover, current standards cannot differentiate unequivocally between acceptable and affected microstructures, making the development of an appropriate quality control test a priority for the oil and gas industry. Recently, Alloy 725 failures were associated with the precipitation of nanoscale Cr- and Mo-rich phases at grain boundaries (GBs). Since these intergranular precipitates could lead to Cr- and Mo-depletion along the decorated GBs (i.e., sensitization), the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test was explored as an alternative approach to detect affected microstructures. Herein, the DL-EPR technique was optimized for Alloy 725 by testing three types of samples with different degrees of sensitization, including a full GB-decorated microstructure that was shown prone to hydrogen embrittlement in oil and gas service. The optimized DL-EPR test conditions were 2 M HCl + 1 M H2SO4 + 10−4 M KSCN aqueous solution at 30 °C with a 1.667 mV s−1 scan rate and a vertex potential of Ecorr + 700 mV. Results were reproducible and consistent with the degree of GB decoration determined using metallographic methods. The test procedure developed herein could lead to the standardization of the DL-EPR method for Alloy 725.

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Corrosion Study of Base Material and Welds of a Ni–Cr–Mo–W Alloy

Cited by 12 publications

References 17 publications

Synthetic Effect of Cr and Mo Elements on Microstructure and Properties of Laser Cladding NiCrxMoy Alloy Coatings

Synthetic Effect of Cr and Mo Elements on Microstructure and Properties of Laser Cladding NiCrxMoy Alloy Coatings

Corrosion Protection of Monel Alloy Coated with Graphene Quantum Dots Starts with a Surge

Detecting Intergranular Phases in UNS N07725: Part I. Adapting the Double-Loop Electrochemical Potentiokinetic Reactivation Test

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