Browsing by Author "Samuel, A."

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A Phase Transformation Enthalpy Parameter for Modeling Quench Hardening of Steels
(Springer, 2024) Samuel, A.; Pranesh Rao, K.M.P.; Prabhu, K.N.
The effect of phase transformations on the steel/quenchant interfacial heat flux during quench hardening heat treatment is investigated in the present work. Experimental and modeling approaches comprising the inverse heat conduction problem (IHCP) were employed to analyze the thermal behavior of different steel grades with varying section thicknesses. The results revealed that phase transformation led to a distinctive pattern of the interfacial heat flux, characterized by a dip and subsequent rise. We observed that increasing the section thickness increases the surface heat flux for stainless steel probes without phase transformation. In contrast, the surface heat flux decreased with thicker sections in phase transformation. The increased heat evolved due to the latent heat liberation during phase transformation, and a reduction in thermal diffusivity due to increased specific heat caused a fall in the heat flow rates. Furthermore, the study proposed a phase transformation enthalpy parameter (ΔQ) to access the enthalpy change during quenching. ΔQ was consistent for a specific steel grade and independent of section thickness but varied with the cooling rate or quench media. The incorporation of phase transformation in the quenching heat transfer model is complex due to the required material data, including TTT/CCT diagrams and thermophysical properties that vary with steel grade. The study suggests directly incorporating the ΔQ values into the heat conduction equation or the IHCP model with phase transformation, simplifying the simulation process and minimizing data inputs. A database on ΔQ as a function of temperature and cooling rate would facilitate heat transfer modeling during quench hardening. © 2023, The Minerals, Metals & Materials Society and ASM International.
Assessment of Heat Transfer Characteristics of Transesterified Waste Sunflower Cooking Oil Blends for Quench Hardening
(Springer, 2022) Samuel, A.; Prabhu, K.N.
Mineral oils used in the heat treatment industry are derivatives of non-renewable petroleum fuel and are toxic and non-biodegradable. Vegetable oils are an ideal substitute for mineral oil due to their superior heat transfer characteristics and eco-friendliness. However, the initial cost of vegetable oils is very high. In addition, the maintenance cost of vegetable oils would be higher due to their poor thermal and oxidative stability than mineral oil. In this context, recycling and reusing waste cooking oil could be a cheaper and eco-friendly alternative. In this study, the fatty acid methyl ester (FAME) produced from the waste sunflower cooking oil through transesterification was blended with sunflower and mineral oils at various proportions. The cooling characteristics of the FAME/oil blends were assessed using the cooling curve analysis according to ASTM D6200 and ISO9950 standards. A solution to the inverse heat conduction problem was used to estimate the spatiotemporal metal/quenchant interfacial heat flux. The uniformity of heat flux was analyzed. The results indicated that blending waste cooking oil-derived FAME in sunflower oil up to 60 vol.% and mineral oil up to 50 vol.% provided comparable cooling characteristics to pure oils. The estimated heat flux transients showed a marginal decrease in peak heat flux for FAME blends in sunflower oil, whereas an increased peak heat flux with mineral oil. The FAME blends less than 60 vol.% in sunflower oil showed higher cooling uniformity. With mineral oil, the blend proportion of up to 50 vol.% increased cooling uniformities compared to pure oil. The characteristic cooling time (t85) increased with the increase in FAME blends in oils. However, the distribution of t85 in the quench probe was uniform for FAME/oil blends. © 2022, ASM International.
Assessment of the Performance of Sn 3.5Ag/Cu Solder Joint Under Multiple Reflows, Thermal Cycling and Corrosive Environment
(2018) Samuel, A.; Tikale, S.; Prabhu, K.N.
The solder joint performance of Sn 3.5Ag/Cu combination was studied under multiple reflows, thermal cycling and exposure to the corrosive environment. Factorial experiment was carried out to assess the effect of individual parameters and the interaction of parameters on the shear strength of the solder joint. The results showed that the combination of thermal cycling and immersion in corrosive media resulted in the maximum decrease in the shear strength followed by the combination of multiple reflows and corrosive media. The shear strength reduced with the increase in immersion duration in corrosion medium. Factorial experiment was analyzed using analyis of variance (ANOVA). The results indicated that the individual parameters had a significant effect, whereas the effect of interaction of these parameters was less significant on the performance of the solder joint. Fracture surface indicated mixed mode of failure and the occurrence of fracture predominantly in the bulk solder. 2018, The Indian Institute of Metals - IIM.
Assessment of the Performance of Sn–3.5Ag/Cu Solder Joint Under Multiple Reflows, Thermal Cycling and Corrosive Environment
(Springer, 2018) Samuel, A.; Tikale, S.; Prabhu, K.N.
The solder joint performance of Sn–3.5Ag/Cu combination was studied under multiple reflows, thermal cycling and exposure to the corrosive environment. Factorial experiment was carried out to assess the effect of individual parameters and the interaction of parameters on the shear strength of the solder joint. The results showed that the combination of thermal cycling and immersion in corrosive media resulted in the maximum decrease in the shear strength followed by the combination of multiple reflows and corrosive media. The shear strength reduced with the increase in immersion duration in corrosion medium. Factorial experiment was analyzed using analyis of variance (ANOVA). The results indicated that the individual parameters had a significant effect, whereas the effect of interaction of these parameters was less significant on the performance of the solder joint. Fracture surface indicated mixed mode of failure and the occurrence of fracture predominantly in the bulk solder. © 2018, The Indian Institute of Metals - IIM.
Critical Heat Transfer Coefficients for Selection of Quench Media during Heat Treatment of Steels
(Springer, 2025) Samuel, A.; Pranesh Rao, K.M.; Prabhu, K.N.
The depth of hardness in during quench hardening of steels depends on the steel composition, section thickness, and the boundary heat transfer coefficient. A simulation study is performed in the present work to optimize the heat transfer coefficients for selecting quenchants for a particular grade of steel and section thickness. The simulation study is performed by solving phase transformation coupled transient heat conduction equation using the finite element method. The finite element model adopted in this work uses the one-dimensional radially symmetric model with a constant heat transfer coefficient boundary condition at the surface. The variables in the simulation study are the carbon content, the diameter of steel, and the heat transfer coefficients. The effect of these variables on the martensite formation is studied. A critical heat transfer coefficient is defined corresponding to a 50 pct. martensite transformation at the core of the steel cylindrical specimens. The critical heat transfer coefficient increased with the increase in the diameter; whereas, it showed a parabolic relation with the carbon content. The usefulness of the study in selecting a suitable quenchant for quench hardening of plain carbon steels with varying carbon content is illustrated. © ASM International 2024.
Effect of process variables on heat transfer and the product quality during layer deposition of Al4043 alloy by wire arc additive manufacturing
(John Wiley and Sons Inc, 2025) Raghavendra Pai, K.; Vijayan, V.; Samuel, A.; Prabhu, K.N.
In the present work, heat transfer dynamics between the substrate and the deposited metal is investigated to assess its effect on the evolution of defects and the quality of the product. A series of experiments involving the deposition of Al4043 wire were conducted on Al4043 aluminum alloy substrate at a voltage range of 13–19 V. A one-dimensional inverse computational model was adopted to estimate the heat flux transients. The metal/substrate interfacial heat flux was correlated with the microstructure evolution during the solidification of the metal. The experimental results clearly indicated that heat transfer plays a dominant role in the final finish and quality of the product and is controlled by variables, such as voltage, gas flow rate (GFR), wire feed rate (WFR), and forward traversal speed. At an integral heat flow (HF) in the range of 3000–5000 kJ/m2 corresponding to voltages between 13.8 and 14.5 V, argon GFR of 12–15 L/min, and a WFR of 4.1 mm/min, the porosity in the additively manufactured component was found to be minimum. The ultimate tensile strength was found to be 65 and 76 MPa, corresponding to the voltage of 13.5 and 14.5 V, respectively, and decreased to 25 MPa for a higher voltage of 19 V. At the GFR range of 8–10 L/min, the HF was in the range of 450–510 kJ/m2 with increased porosity (33%–42%). Porosity was found to decrease (15%–22%) with 12–15 L/min range of GFR and the corresponding HF was in the range of 700–950 kJ/m2. The specimens fabricated under these optimal parameters exhibited superior mechanical properties. © 2024 Wiley Periodicals LLC.
Estimation of Heat Flux Transient During Quench Hardening of Varying Diameter Steel Probes Using IHCP-Phase Transformation Coupled Model
(ASM International, 2023) Samuel, A.; Nayak, U.V.; Pranesh Rao, K.M.P.; Prabhu, K.N.
The phase transformation model is coupled with the inverse heat conduction problem (IHCP) to estimate the steel/quenchant interfacial heat flux. Cylindrical steel probes having section thicknesses 25 and 50mm, respectively, and lengths 30mm were made from medium and high carbon steels (AISI 1045 and 52100). The probes were quenched in mineral, neem, and sunflower oils. The cooling curves at the centre and near the surface of steel probes were recorded. The near-surface cooling curve was used as a reference temperature data in the IHCP algorithm for the estimation of surface heat flux, whereas the cooling curve at the centre was used as the boundary condition of the axisymmetric model of the probe. The effect of phase transformation on the metal/quenchant interfacial heat flux was indicated by a kink and rise of heat flux. The increase in the section thickness of the probe from 25 to 50mm decreased the magnitude of the heat flux. Increasing section thickness increases the phase transformation, increasing the resistance to heat flow at the metal/quenchant interface. Â© Â© 2023 ASM InternationalÂ®
Experimental investigation of heat transfer characteristics of polyethylene glycol (PEG) based quench media for industrial heat treatment
(Elsevier Inc., 2023) Soni, A.; Samuel, A.; Prabhu, K.
Aqueous polymer quenchants are now increasingly used in the quench hardening of steels. The inverse solubility property of polymer media leads to polymer film encapsulation of the quenched component, followed by an instantaneous rupture of the polymer film. The film boiling stage is absent, thus improving heat transfer uniformity. In the present investigation, the effect of molecular weight of Polyethylene glycol (PEG) on heat transfer characteristics of PEG/water quenchants with concentrations of 5, 10, and 20 vol% was studied. The cooling curve analysis is performed to assess the cooling characteristics. Spatially dependent surface heat flux transients are estimated using the inverse heat conduction method. The rewetting kinematics is analyzed by videography and acoustic analysis of polymer film rupture during quenching. The results indicated that an increase in the molecular weight of PEG from 200 to 6000 changed the rewetting kinematics from a local wetting front movement to an instantaneous rupture of the polymer film. The change in the rewetting kinematics is reflected in the surface heat flux, indicating an increased uniformity of heat transfer. The film rupture acoustics showed that the polymer film's instantaneous breakup had a higher sound intensity than the one showing wetting front motion. © 2023 Elsevier Inc.
Heat Transfer and Deposition Strategies for Enhanced Mechanical Performance of Wire Arc Additively Manufactured SS316L Alloy
(Springer, 2025) Pai, K.R.; Vijayan, V.; Samuel, A.; Prabhu, K.N.
The work investigates the effect of various deposition strategies for wire arc additive manufacturing of SS316L on an SS304 substrate for industrial applications. Droplet deposition of SS316L on an SS304 substrate at varying current values (60–130 A) identifies the operational range for line deposition. The wettability, contact angle and spread area are evaluated along with heat flux transients for each current value. Heat flow calculated during line deposition at 90 A for horizontal and vertical substrates was 34297 kJ/m2 and 24137 kJ/m2 respectively. The corresponding values of porosity and micro-hardness indicate superior deposition at 90 A. Further investigation on deposition strategies such as interlayer current change with and without dwell time, deposition at 90 A with a dwell time of 30 s for five cycles, preheated substrates and Continuous Multi-Pass Deposition with 2 s is explored. Heat flux transients are computed for every deposition cycle using an inverse solver. Heat flow was found to be 63260 kJ/m2 and 58863 kJ/m2 for the 15th layer of interlayer current change of 90 ± 10 A and constant current of 90 A with dwell time respectively. By altering deposition parameters such as interlayer time gap and current the chromium content achieved through high-current density deposition significantly increased from 17.2% to 26% and 25.4% respectively. The ultimate tensile strength for the 80A sample without deposition strategies was found to be lower. Columnar grain morphology with dendritic structure was observed at higher currents. Finer equiaxed grains with lower interlayer fusion were observed at lower currents. Finer grain growth across the layers was achieved by adjusting the current between cycles in response to observed heat flux transients. EBSD analysis reveals the formation of brass texture with {110} in deposition strategies involving time gap and interlayer current change, indicating directional solidification thereby enhancing the overall mechanical performance of the as-deposited SS316L. © ASM International 2025.
Heat Transfer Characteristics and Cooling Performance of Treated Kitchen Coconut Oil
(ASM International, 2021) Roy, S.S.; Samuel, A.; Prabhu, K.N.
Quenching is one of the most basic and widely used heat-treatment processes. Mineral Oil or petroleum oil base stocks are the conventional quench media used for quench hardening heat treatment since the 19th century. However, mineral oils are not environment friendly as they are toxic, non-biodegradable, and non-renewable. Many alternative ecofriendly quenchants have been developed to replace mineral oil such as vegetable oils, polymer quenchants, and nanofluids. Although most of the vegetable oils show superior cooling performance to mineral oil, their practical application is limited owing to their high cost of production and low thermal stability. In this study, the kitchen coconut oil was chemically treated and its cooling performance and heat transfer characteristics were assessed and compared with that of refined coconut oil and mineral oil. The thermophysical properties of chemically treated waste cooking oil were found to be higher than refined and mineral oils. Chemically treated oil showed better wettability. The quenching experiments were conducted using an Inconel 600 standard probe according to ISO 9950 and ASTM D 6200 standards. The vapor blanket stage was shorter for the chemically treated oil as compared with refined and mineral oils. Inverse heat conduction problem (IHCP) was solved for estimating heat flux transients from the temperature data and thermo-physical properties of the Inconel probe. The average peak heat flux was highest for chemically treated oil compared to both refined coconut oil and mineral oil. Â© Â© 2021 ASM InternationalÂ® All rights reserved.
Reprocessed waste sunflower cooking oil as quenchant for heat treatment
(Elsevier Ltd, 2020) Prathviraj, M.P.; Samuel, A.; Prabhu, K.N.
The growing concern to minimize the use of petroleum derived mineral oil in heat treatment industries has led to the search for alternative eco-friendly quenchants. Although vegetable oils seem to be a viable option, the higher cost and inferior thermal and oxidation stability have limited their application in the heat treatment industry. The reuse of waste cooking oils for industrial heat treatment would not only make quenchants cost-efficient but also environment friendly. In this study, the cooling performance of waste sunflower cooking oil was assessed and compared with that of unused sunflower cooking and mineral oils. The waste sunflower oil was made suitable for quenching by cleaning and chemical treatment. The experiment to assess the suitability of reprocessed oil for quenching was conducted using an Inconel 600 standard probe according to ISO 9950 and ASTM D 6200 standards. The thermal history acquired while quenching of the probe was used to estimate the surface heat flux transients. The results indicated that the chemically treated waste sunflower cooking oil had a higher cooling performance than that of unused sunflower and the mineral oils. A good agreement was found between the heat flux transients and hardness data obtained with the quenched AISI 4140 steel probe. The simulation of temperature and hardness distribution indicated more uniformity along the length of the probe indicating more uniform cooling with chemically treated waste sunflower cooking oil. © 2020 Elsevier Ltd
Residual Stress and Distortion during Quench Hardening of Steels: A Review
(Springer, 2022) Samuel, A.; Prabhu, K.N.
Quench hardening is a widely used heat treatment process for achievingÂ better mechanical properties in carbon steels. However, when high quench-sensitivity steel components having thin sections are quenched, they may get distorted due to thermal and phase transformation stresses. Appropriate steps have to be taken to minimize residual stresses and distortion during quenching operationÂ in the heat-treating industry. Many factors such as quenchant type, quench severity, quenching process variables, the geometry of the component, and material properties significantly affect the evolution of residual stresses.Â The heat transfer from the metal surface to the quench medium is the critical physical phenomenon that drives the microstructure evolution and residual stresses during quenching. The nonuniformity in heat transfer between the heated metal and the quench medium is the key source of residual stress development in the quenched material. Modeling and simulation of the quenching process can predict the residual stress distribution in the quenched sample andÂ the evolution of quench cracks and component failure. Optimizing quenching process conditions and selecting appropriate quenchants minimize residual stresses and distortion. One of the requirements for improving the accuracy of simulation models is theÂ use of reliable spatiotemporal heat transfer boundary conditions. The present review addresses the evolution of residual stresses during quenching, factors affecting residual stresses such as geometry and section thickness of the quenched part, cooling uniformity, quenchant selection, and the interrelation between heat transfer and residual stresses. The methods to minimize residual stress and distortionÂ in quenched parts are discussed. Â© 2022, ASM International.
Residual Stress and Distortion during Quench Hardening of Steels: A Review
(Springer, 2022) Samuel, A.; Prabhu, K.N.
Quench hardening is a widely used heat treatment process for achieving better mechanical properties in carbon steels. However, when high quench-sensitivity steel components having thin sections are quenched, they may get distorted due to thermal and phase transformation stresses. Appropriate steps have to be taken to minimize residual stresses and distortion during quenching operation in the heat-treating industry. Many factors such as quenchant type, quench severity, quenching process variables, the geometry of the component, and material properties significantly affect the evolution of residual stresses. The heat transfer from the metal surface to the quench medium is the critical physical phenomenon that drives the microstructure evolution and residual stresses during quenching. The nonuniformity in heat transfer between the heated metal and the quench medium is the key source of residual stress development in the quenched material. Modeling and simulation of the quenching process can predict the residual stress distribution in the quenched sample and the evolution of quench cracks and component failure. Optimizing quenching process conditions and selecting appropriate quenchants minimize residual stresses and distortion. One of the requirements for improving the accuracy of simulation models is the use of reliable spatiotemporal heat transfer boundary conditions. The present review addresses the evolution of residual stresses during quenching, factors affecting residual stresses such as geometry and section thickness of the quenched part, cooling uniformity, quenchant selection, and the interrelation between heat transfer and residual stresses. The methods to minimize residual stress and distortion in quenched parts are discussed. © 2022, ASM International.
The Effect of Thermal Quench Cycling on the Stability and Heat Transfer Characteristics of Transesterified-Epoxidized Used Cooking Oil Blended Quench Medium
(Springer, 2024) Samuel, A.; Prabhu, K.N.
Mineral oil is a widely used quench media in the heat treatment industries. They are derived from petroleum crude oil, and are toxic, and non-biodegradable. Therefore, in order to minimize the use of mineral oil, the fatty acid methyl esters (FAME) derived from the used cooking oil through the transesterification process can be blended with mineral oil. However, due to the high amount of unsaturation, blending of FAME in mineral oil would decrease the thermal-oxidative stability of the oil. Therefore, in the present work, to improve the stability of the mineral/FAME blend quenchant, the unsaturation in the FAME is decreased through epoxidation. The stability of epoxidized FAME/mineral blended oil is assessed by thermogravimetric analysis and thermal quench cycling. The quench cycles were performed using an ISO 9950 Inconel 600 standard probe. The viscosity and cooling performance of the oil were assessed periodically after the 1st, 10th, 50th, and 100th quench cycle. Investigation of cooling performance was performed by carrying out cooling curve analysis and estimating metal/quenchant interfacial heat flux tranisents. The results indicated that the thermal stability of the blend quenchant was improved with the epoxidation of FAME. The relative increase in viscosity was lower for blend quenchants than that for the mineral oil. The epoxidized FAME/mineral oil blend showed comparable cooling performance as that of mineral oil as the number of quench cycles were increased. © ASM International 2023.
Thermal conformance parameters for assessment of heat transfer between similar and dissimilar metal contacts
(John Wiley and Sons Inc, 2024) Pathumudy, R.D.; Samuel, A.; Prabhu, K.N.
A novel approach to assess the thermal conformance between two metallic materials under transient conditions was proposed in the present investigation. Thermal conformance parameters (ƞ, ϴ, tg) were defined to quantify the contact condition between a metal–metal interface. To assess the effect of load and thermophysical properties of the sink and source materials on the degree of thermal conformance, a thermal conformance assessment parameter (TCAP) was proposed. Heat flux transients at the thermal interface was estimated by using an inverse heat conduction approach for various similar and dissimilar metallic surfaces in contact such as Cu─Cu, Al─Al, Al─Cu, and Cu─Al under both load and no load conditions. Commercially available silicone grease (SG) and thermal grease (CTG) were used as thermal interface materials (TIMs). The thermal conformance parameters increased with the increase in load for all the combinations of interfaces with and without TIMs. It was observed that, except for the copper–copper combination, thermal conformance parameters showed a linear relation with the TCAP. The enhancement in the heat transfer due to the application of load and TIM was validated by determining the maximum temperature difference (∆Tmax) across the interface. The experimental study revealed that the ∆Tmax decreases with the application of load and application of TIM leading to enhanced heat transfer. For the copper–copper combination, the thermal conformance depended solely on the load applied. Due to the lower thermal resistance offered by copper source/sink materials, the interfacial resistance between them becomes a dominant factor. The effect of TIM on heat absorbed by the sink was significant for the Cu/Cu interface. © 2024 Wiley Periodicals LLC.