Influence of Austenitizing And tempering Temperature on Microstructure, Substructure and Mechanical Properties of Creep Resistant 9crnb Steel

Bekeč, Pavel; Parilák, Ľudovít; Beraxa, Pavol; Fujda, Martin; Matvija, Miloš

doi:10.37904/metal.2019.705

Cited by 1 publication

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“…Their resistance to oxidation in the flue gas environment is comparable [ 5 , 6 ]. For demanding operating conditions where high corrosion resistance is required while maintaining strength in the creep area, heat-resistant steels P91, P92, or martensitic 9Cr MarBN steels are used [ 7 ]. The failure-free operation conditions of the evaporator are related to: the properties of the steel material of the evaporator tubes (strength at elevated temperature); the temperature and the composition of flue gases acting on the outer surface of tubes; heat transfer conditions through tube walls; and last but not least the properties of feed (boiler) water, which affects the condition of the inner surface.…”

Section: Introductionmentioning

confidence: 99%

Effect of Flue Gases’ Corrosive Components on the Degradation Process of Evaporator Tubes

et al. 2021

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Corrosion of boiler tubes remains an operational and economic limitation in municipal waste power plants. The understanding of the nature, mechanism, and related factors can help reduce the degradation process caused by corrosion. The chlorine content in the fuel has a significant effect on the production of gaseous components (e.g., HCl) and condensed phases on the chloride base. This study aimed to analyze the effects of flue gases on the outer surface and saturated steam on the inner surface of the evaporator tube. The influence of gaseous chlorides and sulfates or their deposits on the course and intensity of corrosion was observed. The salt melts reacted with the steel surface facing the flue gas flow and increased the thickness of the oxide layer up to a maximum of 30 mm. On the surface not facing the flue gas flow, they disrupted the corrosive layer, reduced its adhesion, and exposed the metal surface. Beneath the massive deposits, a local overheating of the inner surface of the evaporator tubes occurred, which resulted in the release of the protective magnetite layer from the surface. Ash deposits reduce the boiler’s thermal efficiency because they act as a thermal resistor for heat transfer between the flue gases and the working medium in the pipes. The effect of insufficient feedwater treatment was evinced in the presence of mineral salts in the corrosion layer on the inner surface of the tube.

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Section: Introductionmentioning

confidence: 99%