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Compositional and Bath Temperature Effects on Heat Transfer During Quenching in Molten NaNO3–KNO3 Salt Mixtures
- Source :
- Journal of Materials Engineering and Performance. 29:1860-1868
- Publication Year :
- 2020
- Publisher :
- Springer Science and Business Media LLC, 2020.
-
Abstract
- The present study involved the assessment of cooling severity of molten NaNO3–KNO3 mixtures which are widely used as quench media for austempering and martempering operations. An Inconel probe instrumented with thermocouples was quenched in molten NaNO3–KNO3 binary mixtures of varying concentration maintained at different quench bath temperatures. The temperature data acquired at various locations in the Inconel probe during quenching was used to calculate the spatially dependent transient heat flux at the metal–quenchant interface. Two critical points corresponding to peak heat extraction rates during the nucleate boiling stage and transition from boiling to convection stage were identified for each quench medium. The variation of average heat flux and average surface temperature corresponding to these critical points was mapped with variation in bath temperature and composition of the quench medium. AISI 4140 steel probes were quenched in these quench media maintained at 300 and 350 °C. The average hardness values measured in steel probes agreed with the cooling performance of these quench media determined using Inconel probe. The degree of uniformity in heat transfer as indicated by the spatial variation of normalized heat energy decreased with the increase in the concentration of KNO3 in the quench medium. A mechanism of boiling heat transfer during quenching based on thermochemical decomposition of the salt was proposed.
- Subjects :
- 010302 applied physics
Quenching
Materials science
Martempering
High Energy Physics::Lattice
Mechanical Engineering
Thermodynamics
02 engineering and technology
021001 nanoscience & nanotechnology
01 natural sciences
Heat flux
Mechanics of Materials
Boiling
0103 physical sciences
Heat transfer
General Materials Science
Molten salt
0210 nano-technology
Inconel
Nucleate boiling
Subjects
Details
- ISSN :
- 15441024 and 10599495
- Volume :
- 29
- Database :
- OpenAIRE
- Journal :
- Journal of Materials Engineering and Performance
- Accession number :
- edsair.doi...........dfb72741cdefa21a9c68bfb16c1998d9