The Response of Nitriding Chemistry to Different Initial Gas Compositions

Özdemir, I. Bedii; Akar, Fırat

doi:10.1007/s11665-015-1585-z

Cited by 6 publications

(1 citation statement)

References 15 publications

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“…The nitriding thickness of the nitriding layer speci cally may change with a change of location in the furnace. This is one of the serious aws in the nitrocarburizing process, as the non-uniform thickness of the nitriding layer, which could lead to deterioration of quality, is affected by local ow conditions as well as the temperature and composition of the atmosphere gas 14,15) . There has, however, been limited research on how ow and heat characteristics in the furnace affect material characteristics.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on Influence of Fan Speed and Swirling Gas Injection on Thermal-Flow Characteristics in Nitrocarburizing Furnace

2017

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This study was carried out to analyze the ow and heat transfer characteristics in a furnace, and to evaluate the in uence of the two major design factors for improving the ow mixing and heat transfer. The grid system was constructed using ANSYS ICEM (V.17.0), and numerical simulations were conducted using the commercial CFD code (ANSYS Fluent V.17.0). The fan plays an important role in ow mixing and convective heat transfer in the furnace. Accordingly, temperature uniformity was improved with an increase in the fan speed owing to an enhancement of the convective heat transfer. Moreover, when swirl ow was applied to the inlet gas, temperature uniformity was improved in the lower section of the furnace. This is because the swirl ow of the inlet gas improved the ow mixing in the vicinity of the gas inlet where it is not affected by the rotational force of the fan. Controlling the swirl intensity of the inlet gas with lower fan speeds is more energy ef cient because ow mixing and temperature uniformity could be improved suf ciently.

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Section: Introductionmentioning

confidence: 99%

Numerical Investigation on Influence of Fan Speed and Swirling Gas Injection on Thermal-Flow Characteristics in Nitrocarburizing Furnace

2017

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Parameter Optimization of Nitriding Process Using Chemical Kinetics

Özdemir

Akar

Lippmann³

2016

Metall Mater Trans A

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Local Dynamics of Chemical Kinetics at Different Phases of Nitriding Process

Özdemir

Akar

2015

J. of Materi Eng and Perform

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The local dynamics of chemical kinetics at different phases of the nitriding process have been studied. The calculations are performed under the conditions where the temperature and composition data are provided experimentally from an in-service furnace. Results are presented in temporal variations of gas concentrations and the nitrogen coverage on the surface. It is shown that if it is available in the furnace, the adsorption of the N 2 gas can seemingly start at temperatures as low as 200°C. However, at such low temperatures, as the diffusion into the material is very unlikely, this results in the surface poisoning. It becomes clear that, contrary to common knowledge, the nitriding heat treatment with ammonia as a nitrogen-providing medium is possible at temperatures like 400°C. Under these conditions, however, the presence of excess amounts of product gas N 2 in the furnace atmosphere suppresses the forward kinetics in the nitriding process. It seems that the best operating point in the nitriding heat treatment is achieved with a mixture of 6% N 2 . When the major nitriding species NH 3 is substituted by N 2 and the N 2 fraction increases above 30%, the rate of the forward reaction decreases drastically, so that there is no point to continue the furnace operation any further. Hence, during the initial heating phase, the N 2 gas must be purged from the furnace to keep its fraction less than 30% before the furnace reaches the temperature where the reaction starts.

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The Response of Nitriding Chemistry to Different Initial Gas Compositions

Cited by 6 publications

References 15 publications

Numerical Investigation on Influence of Fan Speed and Swirling Gas Injection on Thermal-Flow Characteristics in Nitrocarburizing Furnace

Numerical Investigation on Influence of Fan Speed and Swirling Gas Injection on Thermal-Flow Characteristics in Nitrocarburizing Furnace

Parameter Optimization of Nitriding Process Using Chemical Kinetics

Local Dynamics of Chemical Kinetics at Different Phases of Nitriding Process

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