Conference Papers
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/28506
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Item Heat transfer during immersion quenching in MWCNT nanofluids(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Nayak, U.; Prabhu, K.Quench heat treatment consists of rapid cooling of steel alloys after austenetization by subjecting them to cooling in a suitable cooling medium. At the heart of quench treatment is the transient heat transfer that occurs between the metal surface and the quenchant at their interface. This governs the quality of the component as it influences phase transformation, residual quench stresses and mechanical properties developed. In the present research work, spatially dependent transient heat flux in the axial direction was estimated using cooling curve analyses coupled with inverse heat conduction technique. A standard Inconel 600 probe instrumented with multiple thermocouples and heated to 865°C was quenched in distilled water (DW) and DW based multi walled carbon nanotubes (MWCNT) quench media. For evaluating the cooling performance, nanoquenchants with concentrations of 0.01, 0.1 and 1.0g/lt. were prepared. The cooling rate curve calculated from the measured temperature at the geometric center of the probe and the estimation of spatially dependent heat fluxes showed that the heat extraction during quenching with MWCNT nanoquenchant (0.1g/lt.) was higher than the other quenchants. The measured values of thermal conductivity and viscosities of quenchants did not show any significant variation. © (2015) Trans Tech Publications, Switzerland.Item Wetting kinetics and cooling performance of PAG polymer quenchants(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Pai, A.; Nayak, U.; Pranesh Rao, K.M.; Prabhu, K.The present research work is aimed at the estimation of quench severity Polyalkylene Glycol (PAG) polymer quenchants having varying concentrations. An Inconel600 probe instrumented with thermocouples was used for this purpose. The thermal history at various locations in the probe was used as an input to the inverse heat conduction model. The inverse analysis yields spatially dependent heat flux transients. The quench severity was assessed using the Grossmann technique. The wetting kinematics of quenching was studied by cooling curve analysis. The severity of quenching as measured by the Grossmann’s technique was found to be higher for polymer quenchants. However, the heat flux transients estimated by the inverse technique and rewetting times measured form the cooling curve analysis suggested comparable and uniform heat transfer with polymer quenchants compared to water quenchants. © (2015) Trans Tech Publications, Switzerland.Item Comparative study of the effect of section thickness of steel during quenching in neem and mineral oil(ASM International joanne.miller@asminternational.org, 2017) Nayak, U.; Prabhu, K.N.The cooling behavior of neem and mineral oil was obtained using instrumented ISO 9950 inconel probe. Flash, fire points and the viscosity of quenching media were measured. These oils were used to quench harden AISI 1045 and AISI 1090 grade steel probes of section diameters 25 and 50 mm. (The top and bottom faces of steel probes were coated with insulating paste to minimize end effects of heat transfer during quenching.) The measured temperature data in steel probes were used to estimate spatiotemporal heat flux by solving inverse heat conduction problem at the interface of the probe/quenching medium The estimated heat flux transients, microstructure, and hardness measurements were found to be similar for both oils indicating the potential application of neem oil as quenchant for heat treatment of steels. © © 2017 ASM Internationale All rights reserved.