Predicting the Effect of Applied Potential on Crack Tip Hydrogen Concentration in Low-Alloy Martensitic Steels

Kehler, B. A.; Scully, John R.

doi:10.5006/1.3278484

Cited by 47 publications

(37 citation statements)

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“…For Ni alloys, H production under cathodic polarization is greater on bold-exposed surfaces due to crack tip pH rise above bulk and less-cathodic crack tip potential from IR difference (Figure 2). [29,54] The decrease in crack tip vs bold surface production of C H-Diff is quantified as a function of E A in Figure 5. However, the intensified 3-dimensional stress state at the crack tip and mid-plane of the SENT specimen dominates HEAC over boldly exposed surface locations.…”

Section: Mechanism Informed Modeling Of Ig Heac Kineticsmentioning

confidence: 99%

“…It is assumed that H uptake in the Monel K-500 crack is insensitive to local pH, at constant g H for the expected pH levels above 6, as found elsewhere. [54] This data base was used to determine C H-Diff at each local potential for the value of x 2 /G pertinent to crack opening shape in Monel K-500.…”

Section: E Occluded Crevice Electrochemistry and Local Hydrogen Concmentioning

confidence: 99%

“…[1] through [3] requires determination of a microstructure-specific H uptake relationship, stated as C H-Diff vs the overpotential for H production (g H ), coupled with knowledge of crack tip pH and potential to yield crack tip g H ; all vs E A. [54] Crack-tip pH and potential were established for Monel K-500 using the artificial crevice geometry shown in Figure 1, coupled with the scaling-law approach to relate crevice and crack geometry difference. [68][69][70] The cell consisted of: (a) an acrylic bottom plate with six disk specimens embedded and shorted to form a continuous working electrode (WE), (b) a plastic shim to create the crevice gap (G), and (c) an acrylic top plate to form the crevice and hold micro-reference electrodes (REs) for local potential measurement.…”

Section: E Occluded Crevice Electrochemistry and Local Hydrogen Concmentioning

confidence: 99%

“…[54] Local potential was measured using a Ag/AgCl micro-reference electrode [54,71] calibrated vs a SCE. Local pH was measured using pH indicator paper.…”

Section: E Occluded Crevice Electrochemistry and Local Hydrogen Concmentioning

confidence: 99%

“…[29] This approach was applied to model HEAC in ultra-high strength steels. [42,54] The objectives of this research are to: (1) enhance an accelerated fracture mechanics test method for HEAC in moderate strength alloys, [42,55] (2) quantitatively characterize the HEAC kinetics of aged Monel K-500 in aqueous chloride solution with cathodic polarization, (3) establish C Hr vs applied cathodic potential for Monel K-500, and (4) model the applied potential dependencies of K TH and da/dt II based on crack tip H uptake using Eqs. [1] and [2].…”

Section: Introductionmentioning

confidence: 99%

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Measurement and Modeling of Hydrogen Environment-Assisted Cracking in Monel K-500

Gangloff

Burns

et al. 2014

Metall Mater Trans A

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Hydrogen environment-assisted cracking (HEAC) of Monel K-500 is quantified using slow-rising stress intensity loading with electrical potential monitoring of small crack propagation and elastoplastic J-integral analysis. For this loading, with concurrent crack tip plastic strain and H accumulation, aged Monel K-500 is susceptible to intergranular HEAC in NaCl solution when cathodically polarized at À800 mV SCE (E A , vs saturated calomel) and lower. Intergranular cracking is eliminated by reduced cathodic polarization more positive than À750 mV SCE . Crack tip diffusible H concentration rises, from near 0 wppm at E A of À765 mV SCE , with increasing cathodic polarization. This behavior is quantified by thermal desorption spectroscopy and barnacle cell measurements of hydrogen solubility vs overpotential for planar electrodes, plus measured-local crevice potential, and pH scaled to the crack tip. Using crack tip H concentration, excellent agreement is demonstrated between measurements and decohesion-based model predictions of the E A dependencies of threshold stress intensity and Stage II growth rate. A critical level of cathodic polarization must be exceeded for HEAC to occur in aged Monel K-500. The damaging-cathodic potential regime likely shifts more negative for quasi-static loading or increasing metallurgical resistance to HEAC.

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Section: Mechanism Informed Modeling Of Ig Heac Kineticsmentioning

confidence: 99%

Section: E Occluded Crevice Electrochemistry and Local Hydrogen Concmentioning

confidence: 99%

Section: E Occluded Crevice Electrochemistry and Local Hydrogen Concmentioning

confidence: 99%

“…[54] Local potential was measured using a Ag/AgCl micro-reference electrode [54,71] calibrated vs a SCE. Local pH was measured using pH indicator paper.…”

Section: E Occluded Crevice Electrochemistry and Local Hydrogen Concmentioning

confidence: 99%