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Pitting Biocorrosion in Internal Pipeline Welds
Published in Richard B. Eckert, Torben Lund Skovhus, Failure Analysis of Microbiologically Influenced Corrosion, 2021
Vitor Liduino, João Payão-Filho, Márcia Lutterbach, Eliana Sérvulo
The surface roughness of the weld beads was characterized in three different positions of each coupon to calculate the average value using a profilometer (Bruker Contour GT-K1). The welded joints were sectioned by wet abrasion for microstructural analysis of the BM, HAZ, and WM. The surfaces underwent abrasion using sandpaper with different granulometries (100, 220, 320, 400, 600, and 1,200 grit) and then were polished with diamond paste (sequence 6 µm, 3 µm, and 1 µm). To reveal the microstructure, nital 2% (2% nitric acid in ethyl alcohol) was used according to standard metallography procedures. The microstructure and nonmetallic inclusions were observed using a Zeiss Axio Imager M2m optical microscope coupled to an AxioCam 503 digital camera. Pitting corrosion was investigated according to ASTM G-46/94 (2005) standard employing a 3D measurement system (Zeiss Smartzoom 5 microscope). The evolution of pitting was assessed by quantifying pitting parameters including the: (i) density (the total number of pits per m2) and (ii) average depth of five random pits present in each weld zone (BM, HAZ, and WM).
Metallography and Material Characterization
Published in Zainul Huda, Metallurgy for Physicists and Engineers, 2020
Etching. Metallographic etching involves revealing the microstructure of the metal through selective chemical attack. In alloys with more than one phase, etching creates contrast between different regions through differences in the reflectivity of the different phases. In pure metals or solid-solution alloys, the rate of etching is affected by crystallographic orientation resulting in contrast between grains. The etching reagent preferentially etches high-energy sites such as grain boundaries; which results in a surface relief that enables different crystal orientations, grain boundaries, phases, and precipitates to be easily distinguished. For etching carbon steels, nital (2% nitric acid-98% alcohol) solution is used. For etching stainless steel or copper alloys, a saturated aqueous solution of ferric chloride (Fe3Cl) containing a few drops of HCl is used. Metallographic etching is applied using a grit-free cotton bud wiped over the surface a few times; the specimen should then immediately be washed in alcohol and dried.
Deformed Steel Fiber Pull-Out Mechanics: Influence of Steel Properties
Published in R. N. Swamy, Fibre Reinforced Cement and Concrete, 1992
M. R. Krishnadev, S. Berrada, N. Banthia, J.-F. Fortier
Standard metallographic techniques were used for preparing fiber specimens for microscopic observations. Normally, 2% nital was used for etching samples to reveal microstructural features. For observing the surface of the fiber after pull-out, a part of pulled-out fiber was mounted in plexiglass and finely polished. These samples were examined in a JEOL SEM II scanning electron microscope operating at 25 kV. To reveal dislocation substructure and copper precipitation, transmission electron microscopy was employed. Thin foils were prepared by electrochemical polishing method (7).
Experimental study on application of gas metal arc welding based regulated metal deposition technique for low alloy steel
Published in Materials and Manufacturing Processes, 2022
Din Bandhu, Jay J. Vora, Subhash Das, Ashish Thakur, Soni Kumari, Kumar Abhishek, M. Nagaphani Sastry
The welded specimens were pulled out in such a way that the entire region surrounding the weld bead could be investigated for metallurgical analysis. Metallographic inspections namely optical microscopy and scanning electron microscopy (SEM) were accomplished to divulge the microscopic details. The specimens were made ready through the traditional polishing method that includes polishing using SiC emery sheets (with a varying grit size of 220–1000) accompanied by disc polishing for the mirror-finish surface. As an etchant, 2% Nital was used to divulge the desired microstructures. The etched samples were held individually beneath the inverted microscope (Model: GX-51, Olympus, Tokyo, Japan) to illustrate and assess distinct microstructures present in the BM, HAZ, and WZ. Scanning electron microscopy (Model: JSM-6380A, JEOL Ltd, Tokyo, Japan) equipped with a unit for energy dispersive x-ray (EDX) spectroscopy was also performed for a better understanding of precipitates in different zones of weldments.
Tribological behaviour of the hardfacing alloys utilised to fabricate the wear parts of an excavator bucket
Published in Transactions of the IMF, 2021
Biswajit Das, Kumar Sawrav, Shiv Brat Singh, P. P. Bandyopadhyay
Small pieces of dimension 1 × 1 mm2 were cut off from the hardfaced coupons for further investigation. Cross sections of test coupons were cold mounted first, and polished subsequently using SiC papers and diamond pastes for microstructural investigation. Next, the polished surfaces were etched using 5% nital etchant. Finally, the cross-sections were observed under an optical microscope (Zeiss, Jena, Germany) and a scanning electron microscope (SEM) (Zeiss, EVO 15, Jena, Germany) equipped with energy dispersive X-ray spectroscopy (EDX) facility. The hardness of the bulk samples was measured using a hardness tester under a load of 100 g, and 15 s dwell time. An average of ten readings together with standard deviation was obtained. The hardnesses of individual phases present in the samples were measured using another hardness tester (ZHµ Zwick Roell, Ulm, Germany) under a load of 25 g, and 15 s dwell time. In this case, too, an average of ten readings was also obtained.
Development of submerged arc welding flux from rice straw ash
Published in Materials and Manufacturing Processes, 2023
Jatinder Garg, Kulwant Singh, Love Kumar, Lalta Prasad
To study and compare the metallurgical properties of the weld metal deposited with the original and developed flux, the specimen used for bead geometry studies was further polished to a mirror finish following the standard metallurgical procedures. The polished surfaces were etched with 2% nital solution to reveal their microstructure. The specimens were observed under the optical microscope, and the image micrographs were captured from various zones at 200X magnification. It was followed by the Field-emission scanning electron microscopy (FESEM) at 400X and Energy dispersive spectroscopy (EDS) analyses. The results obtained are presented in the next section and discussed in detail.