Effect of Cl− and rust layer on stress corrosion cracking behavior of X100 steel base metal and heat-affected zone in marine alternating wet/dry environment

The effects of two temper conditions (T4 and T6 heat treatments) upon the stress corrosion cracking (SCC) of AA6061 plates have been investigated in this work. AA6061 alloys were double-side-welded by the tungsten inert gas (TIG) welding method. SCC behavior of both the as-welded and as-received alloys was reported. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to determine the precipitate structure of the thermal-altered zones and the base metal (BM), and also the hardness variations were examined using microhardness testing (Vickers hardness). The small-size precipitate structures in the T6 tempered alloy and the coarser precipitate structures in the T4 tempered alloy were found by microstructural investigations. As a result, T4 temper heat treatment of this alloy considerably reduced its susceptibility to stress corrosion cracks due to relatively coarse and more separate precipitate morphology. In welded specimens, SCC failure occurred in the area between the heat-affected zone (HAZ) and the base metal. Stress corrosion resistance in the fusion zone was strong in both temper conditions. The aim of this work was to obtain the effects of heat treatment and welding on SCC behavior of the age-hardenable aluminum alloy. The authors conclude that a deep insight into the SCC resistance of AA6061 alloy indicates the precipitate particle distributions and they are the key point for AA6061 alloy joints in chloride solution.

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Stress Corrosion Cracking of Friction Stir-Welded AA-2024 T3 Alloy

Materials ◽

10.3390/ma13112610 ◽

2020 ◽

Vol 13 (11) ◽

pp. 2610 ◽

Cited By ~ 3

Author(s):

Marina Cabrini ◽

Sara Bocchi ◽

Gianluca D'Urso ◽

Claudio Giardini ◽

Sergio Lorenzi ◽

...

Keyword(s):

Friction Stir Welding ◽

Strain Rate ◽

Stress Corrosion ◽

Base Metal ◽

Stress Corrosion Cracking ◽

Heat Affected Zone ◽

Corrosion Cracking ◽

Slow Strain Rate ◽

Friction Stir ◽

Aa 2024

The paper is devoted to the study of stress corrosion cracking phenomena in friction stir welding AA-2024 T3 joints. Constant load (CL) cell and slow strain rate (SSR) tests were carried out in aerated NaCl 35 g/L solution. During the tests, open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were measured in the different zones of the welding. The results evidenced initial practical nobilty of the nugget lower compared to both heat-affected zone and the base metal. This effect can be mainly ascribed to the aluminum matrix depletion in copper, which precipitates in form of copper-rich second phases. In this zones, no stress corrosion cracking was noticed, but well-evident stress-enhanced intergranular corrosion occurred. This is due to the uneven distribution of platic deformation during the slow strain rate tests. Higher strain values are localized at the heat affected zone, where softening occurs. On the contrary, stress values at the nugget are not sufficient to favor both the initiation and propagation of stress corrosion cracks. In the range of processing parameter studied in this experimental work, the stress corrosion cracking susceptibility of the friction stir welding (FSW)-ed alloy is then similar to that of the base metal.

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Studies on the influence of sodium hydroxide concentration on stress corrosion cracking behavior of P91 steel weldment

CORROSION ◽

10.5006/3860 ◽

2021 ◽

Author(s):

Anita Toppo ◽

Sivai Bharasi N ◽

C Das ◽

R.P. George

Keyword(s):

Weld Metal ◽

Stress Corrosion ◽

Sodium Hydroxide ◽

Base Metal ◽

Stress Corrosion Cracking ◽

Corrosion Cracking ◽

Shielded Metal Arc Welding ◽

P91 Steel ◽

Cracking Behavior ◽

Steel Weldment

Influence of sodium hydroxide (NaOH) concentration on the behavior of modified 9Cr- 1Mo (P91) steel weldment with respect to stress corrosion cracking (SCC) resistance was studied in this work. Weldment of P91 steel was prepared by shielded metal arc welding (SMAW) process using modified 9Cr- 1Mo electrode followed by weld heat treatment at 1033 K/1h. SCC experiments were carried out at 473 K at a strain rate (SR) of 1 × 10-6 s-1 in Millipore water (MP) (inert medium) as well as in 1, 2, 3 and 4 M sodium hydroxide (NaOH) medium. Ultimate tensile strength (UTS), yield strength (YS) and % total elongation (%TE) determined from stress-strain plots were found to decrease with increasing concentration of NaOH. SCC susceptibility index (Iscc) evaluated using UTS and % TE was highest for specimen tested in 4M NaOH. Number density of cracks determined by optical microscopy increased with the concentration of NaOH. Also, number of cracks was higher in the base metal than in the weld metal. At highest concentration of 4M NaOH, cracks were also observed in the heat affected zone (HAZ) of the weldmetal. Fractographic studies by Scanning electron microscopic (SEM) showed mixed mode from intergranular to transgranular cracking and vice versa at all concentrations of NaOH. Failure in the base metal was attributed to coarse precipitates, facilitating easy pitting at the precipitate /matrix interface. From the studies it was inferred that weld metal showed better resistance than base metal to SCC in 1-4 M NaOH concentrations.

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