Consideration of intrastructural stresses in the processes connected with the effect of structural nonuniformity on corrosion damages inflicted to heat-transfer tubes

• Published in: Thermal engineering Vol. 61; no. 8; pp. 600 - 605
• Main Authors: Lyubimova, L. L., Makeev, A. A., Zavorin, A. S., Tashlykov, A. A., Artamontsev, A. I., Lebedev, B. V., Fisenko, R. N.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-08-2014
• Subjects: Engineering; Engineering Thermodynamics; Heat and Mass Transfer; Metals and Strength Analysis; inner structural stresses of the first and second kind; density of dislocations; relaxation; passivation; microhardness; profile of X-ray diffraction line; crystallites
• ISSN: 0040-6015; 1555-6301
• DOI: 10.1134/S0040601514060068

The article presents information on local structural nonuniformities in the tube wall metal due to which its individual zones have different susceptibility to corrosion damage processes. The presented information is based on experimental data about the structure of material (microhardness, crystallite size distribution function, and inner structural stresses of the first and second kind depending on the structural flaws density and temperature) obtained using the high-temperature X-radiography method. For a sample made of Grade 20 steel, the temperature range (350–370°C) is experimentally substantiated and determined based on the conditions of relaxing inner structural stresses of the first and second kind in which the crack surface is passivated by oxide film, which prevents the occurrence of stress concentration at the crack edge and crack propagation.