Journal Articles

Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884

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Author: search.filters.author.Prabhu, K.N.Subject: search.filters.subject.Temperature range

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    Investigation into creep behaviour of Sn-40%Pb alloy using impression creep method
    (2009) Udaya Prasanna, H.U.; Udupa, K.R.; Prabhu, K.N.
    The creep behaviour of Sn-40%Pb hypereutectic alloys cast in the molds made of different materials was investigated using impression creep technique in the temperature range from zero to 32 °C and under the punching stress of 50 MPa. The creep curves.ie, profiles of indentation depth against time are generated and steady state creep rates (SSCRs) are determined. Activation energy was calculated knowing creep rates at different temperature levels. Standard metallographic technique was used to determine the grain size of alloys which were poured into different molds. It was found that SSCR, at all the temperature levels of testing, is a function of grain size of the material. The activation energy being in the range of 10kJ/mol -12 kJ/mol, suggests that the probable creep mechanism is dislocation glide aided by vacancy diffusion. Results of the experiments are discussed.
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    Effect of Bath Temperature on Cooling Performance of Molten Eutectic NaNO3-KNO3 Quench Medium for Martempering of Steels
    (Springer Boston, 2017) Pranesh Rao, K.M.; Prabhu, K.N.
    Martempering is an industrial heat treatment process that requires a quench bath that can operate without undergoing degradation in the temperature range of 423 K to 873 K (150 °C to 600 °C). The quench bath is expected to cool the steel part from the austenizing temperature to quench bath temperature rapidly and uniformly. Molten eutectic NaNO3-KNO3 mixture has been widely used in industry to martemper steel parts. In the present work, the effect of quench bath temperature on the cooling performance of a molten eutectic NaNO3-KNO3 mixture has been studied. An Inconel ASTM D-6200 probe was heated to 1133 K (860 °C) and subsequently quenched in the quench bath maintained at different temperatures. Spatially dependent transient heat flux at the metal–quenchant interface for each bath temperature was calculated using inverse heat conduction technique. Heat transfer occurred only in two stages, namely, nucleate boiling and convective cooling. The mean peak heat flux (qmax) decreased with increase in quench bath temperature, whereas the mean surface temperature corresponding to qmax and mean surface temperature at the start of convective cooling stage increased with increase in quench bath temperature. The variation in normalized cooling parameter t85 along the length of the probe increased with increase in quench bath temperature. © 2017, The Minerals, Metals & Materials Society and ASM International.