• S Prakash

      Articles written in Sadhana

    • The aeronomy experiment

      S Prakash B H Subbaraya V Kumar P N Pareek J S Shirke R N Misra K K Goswami R S Singh A Banerjee

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      The experiments described here were flown onAryabhata and were mainly designed to study the global distribution of suprathermal electrons, ionosphere-magnetosphere coupling, theF-region anomaly and the hydrogen geocorona. The experiments consisted of a retarding potential analyser and two ultraviolet ion chambers. The former was designed for the measurement of the flux of suprathermal electrons in the earth’s atmosphere while the latter was for measuring the intensity of the resonantly scattered hydrogen Lyman alpha (1216 Å) and photoelectronically excited OI (1304 Å) emissions.

    • Erosion–corrosion behaviour of Ni-based superalloy Superni-75 in the real service environment of the boiler

      T S Sidhu S Prakash R D Agrawal Ramesh Bhagat

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      The super-heater and re-heater tubes of the boilers used in thermal power plants are subjected to unacceptable levels of surface degradation by the combined effect of erosion–corrosion mechanism, resulting in the tube wall thinning and premature failure. The nickel-based superalloys can be used as boiler tube materials to increase the service life of the boilers, especially for the new generation tra-supercritical boilers.

      The aim of the present investigation is to evaluate the erosion–corrosion behaviour of Ni-based superalloy Superni-75 in the real service environment of the coal-fired boiler of a thermal power plant. The cyclic experimental study was performed for 1000 h in the platen superheater zone of the coal-fired boiler where the temperature was around 900°C. The corrosion products have been characterized with respect to surface morphology, phase composition and element concentration using the combined techniques of X-ray diffractometry (XRD), scanning electron microscopy/energy-dispersive analysis (SEM/EDAX) and electron probe micro analyser (EPMA). The Superni-75 performed well in the coal-fired boiler environment, which has been attributed mainly to the formation of a thick band of chromium in scale due to selective oxidation of the chromium.

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