As-received (AsRec) EN24 steel was treated with conventional heat treatment (ConHeatTreat) without tempering followed by deep cryogenic treatment (DeepCryoTreat) as a supplemental treatment to study ...its tribological behaviour against alumina without or with mineral oil (MO) under different normal loads of 1 N and 5 N. The ConHeatTreat of the AsRec-EN24 obtained an 218.5% improvement in its hardness as the supplemental DeepCryoTreat of the ConHeatTreat-EN24 resulted in a 11.7% further improvement in its hardness. As a result, the ConHeatTreat-EN24 had the 67.5% and 56.3% lower wear volumes for 1 N and 5 N under dry condition and the 53.6% lower wear volume for 5 N under MO lubrication condition compared to those of the AsRec-EN24, respectively. The DeepCryoTreat-EN24 had the 11.5% and 39.7% lower wear volumes for 1 N and 5 N under dry condition and the unmeasurable wear volume for 5 N under MO lubrication condition compared to those of the ConHeatTreat-EN24, respectively. It could be concluded that the supplemental DeepCryoTreat further improved the hardness and thereby the abrasive wear resistance of the ConHeatTreat-EN24 under both dry and lubrication conditions.
In this work, the impact of deep cryogenic and tempering treatment on the corrosion behavior of AISI 420 (UNS S42000) and AISI 52100 (UNS G52986) steel in 3.5% sodium chloride (NaCl) and sodium ...bicarbonate (NaHCO3) + 0.25% NaCl solution was studied using open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) measurements. The relationship of microstructure and the electrochemical response of differently treated samples was discussed. The results indicated that, compared with the conventional treatment, no significant modification of the electrochemical corrosion behavior after cryogenic treatments was observed. No passive behavior was observed for either AISI 420 or AISI 52100 in 3.5% NaCl, whereas it was observed in NaHCO3 + 0.25% NaCl solution. Different effects of tempering treatment on the corrosion behavior between AISI 420 and AISI 52100 were observed due to different modifications of the microstructure during the tempering process. The amount of retained austenite has a critical role in determining the pitting resistance. The pitting resistance increased with the amount of retained austenite.
Experimental investigation of parallel plate fin and the crosscut pin fin heat sinks where the heating element placed asymmetrically is performed. Theoretical calculations were done and compared with ...the experimental results. A comparative study was made based on their efficiencies, heat transfer coefficient, and the thermal performance. From the experimental results it was found that the average heat transfer coefficient of parallel plate fins is higher than that of crosscut pin fins with many perforations. However the performance efficiency of both the crosscut pin fins and parallel plate fins is similar. A hybrid approach was employed to significantly optimize the distance between the fan and heat sink for parallel plate and crosscut pin fins. Parallel plate heat sink with an average heat transfer coefficient of 46 W/m?K placed at an optimum fan distance of 40-60 mm is selected as the suitable choice for the micro-electronic cooling when the heating element is placed asymmetrically.
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In this study, the effects of deep cryogenic treatment (DCT) on the mechanical and tribological properties of AISI D3 tool steel were investigated together with a systematic correlation between their ...hardness and wear resistance. It was found that conventionally heat treated AISI D3 tool steel samples were significantly hardened via an additional DCT, which was attributed to the more retained austenite elimination, more homogenized carbide distribution and more reduction in carbide size in the samples. As a result, the hardened AISI D3 samples exhibited reductions in their friction and wear during rubbing against alumina and 100Cr6 steel balls under different normal loads due to the effectively hindered removal of surface materials. The results clearly showed that the DCT was an effective way to improve the mechanical and tribological properties of the AISI D3 tool steel samples as the tribological performance of the tool steel samples was significantly influenced by their hardness.
Three types of nanolayered Pd-based metal/p-4H SiC systems, Au/Pd, Au/Pd/Al and Au/Pd/Ti/Pd have been investigated and compared to Pd monolayered metallization regarding the electrical and thermal ...properties. The lowest contact resistivity of 2.8x10-5 .cm2 has been achieved with the Au/Pd/Ti/Pd contact. This contact exhibits excellent thermal stability during long-term heating at temperature of 700oC and at operating temperatures up to 450oC. The surface morphology investigation has shown that despite the observed decrease, the palladium agglomeration has been not avoided completely in the same contact. The dominated surface roughness was measured to be 75 nm. However, the formation of dendrites in certain places leads to increase the surface roughness to 125 nm. The structural analysis revealed that palladium silicides are formed at the interface metal/p-4H SiC which affects on decrease of the barrier height in more than two times and conversion of the contact from Schottky into ohmic.
A developing country like India encounters challenges like exponential increase in population and rising per capita energy consumption which demands an optimum usage of available energy resources. ...Currently the energy demands are mostly met by non renewable energy sources, a system that puts a tremendous pressure on the economy and causes a serious threat to the environment, flora and fauna. Hence, the government and other state nodal agencies in India are taking initiatives to promote the use of the renewable energy sources. In the present study, an attempt has been made to arrive at the overall priorities of the renewable energy sources available in India using Analytical Hierarchy Process (AHP). The important parameters like Cost, Efficiency, Environmental impact, Installed capacity, Estimated potential, Reliability and Social acceptance are considered in this model to identify and rank the renewable energy sources like solar, wind and biomass. A survey based on Delphi technique was conducted in the previous work from which the scales for the aforementioned parameters are fixed. For each attribute, and each pair of alternatives, the outcome of the survey specifies their preference in the form of a fraction between 1/9 and 9. The results show the order of merit as Wind energy (0.501), Biomass energy (0.288), and Solar energy (0.2056) with respect to Indian policies and conditions to meet the future energy demand.
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