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Characterization of deposit layers formed on grey cast iron

Gwoździk Monika

Technical Sciences / University of Warmia and Mazury in Olsztyn

2022

nr 25(1)

107--115

This paper presents the results of diagnostic examinations conducted on the water pipe made of grey cast iron that were operated in conditions for 260 thousand hours. The tube was exposed in a soil. The phase composition of the deposit layers formed on both sides of the tube walls (outside and inside) was examined using optical and confocal microscopy and X-ray diffraction. The obtained XRD test results showed that mainly -FeOOH) and γ-FeOOH is formed on the inside of the pipe wall. In turn, on the outside, in addition to the above-mentioned compounds, also SiO2 is formed. The results of these examinations have shown a higher degradation of pipe on the outer side. The arithmetic mean deviation of the profile from the mean line was 6.23 µm and 8.07 µm for the inner and outer side of the pipe wall, respectively. The work demonstrates the usefulness of material science, especially X-ray structure, topography and surface studies, in characterizing the degradation processes of layers formed on gray cast iron exploited in the water supply industry.

Characterization of oxide layers formed on 10CrMo9-10 steel operated for a long time in the power industry

Gwoździk Monika, Ullrich Christiane, Schimpf Christian, Rafaja David, Kulesza Sławomir, Bramowicz Mirosław

Bulletin of the Polish Academy of Sciences. Technical Sciences

2021

Vol. 69, nr 4

art. no. e137730

This paper presents the results of diagnostic examinations conducted on the coils of super-heaters made of 10CrMo9‒10 steel that were operated in industrial conditions at 480°C for 130 thousand hours. The tube was exposed in a coal-fired boiler. The chemical and phase composition of the oxide/deposit layers formed on both sides of the tube walls (outside – flue-gas side and inside – steam side) and their sequence was examined using optical microscopy, scanning electron microscopy with electron backscatter diffraction and energy-dispersive X-ray spectroscopy, and X-ray diffraction. The changes in the mechanical properties caused by corrosion and aging processes were concluded from the hardness measurements. In addition, the nature of cracks in the oxide layers caused by pressing a Vickers indenter was determined. The results of these examinations have shown a high degradation of steel on the flue-gas inflow side and identified the main corrosion products and mechanisms.