RAPOUCH Jiří VŠCHT v Praze

Spoluautoři BYSTRIANSKÝ Jaroslav

Use of creep-resistant steel P92 in modern power plants enables increase of service temperature up to 650 °C. Some alloying elements (Cr, W) can easily increase their oxidation states and form volatile compounds in high steam parameters environments. Very similar degradation mechanism is observed in strongly oxidizing aqueous environments, where these alloys are subject to transpassive dissolution. Model melts containing constant chromium content (9 wt.%) and variable amount of carbon (0.01 - 0.63 wt. %) and tungsten (1.5 - 4.0 wt. %) were used for study of the influence of alloying elements. Structure of these alloys was characterized using optical and scanning electron microscope. Electrochemical behaviour was evaluated by potentiodynamic method. Model alloys showed to have dissimilar structure compared to industrial melts of P92, however, shapes of their potentiodynamic curves are very similar. The curve in transpassive area is accompanied by formation of substantial local peaks whose position differ according to chemical composition and heat treatment of the alloy. The model alloys were potentiostatically etched in local peaks areas and characterized using scanning electron microscope equipped by EDS analyser.

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