Influence of Oxygen Admixture on Plasma Nitrocarburizing Process and Monitoring of an Active Screen Plasma Treatment
The effect of a controlled oxygen admixture to a plasma nitrocarburizing process using active screen technology and an active screen made of carbon was investigated to control the carburizing potential within the plasma-assisted process. Laser absorption spectroscopy was used to determine the result...
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| Autores principales: | , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/699bf55818fa43778266e4a0b4fead19 |
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| Sumario: | The effect of a controlled oxygen admixture to a plasma nitrocarburizing process using active screen technology and an active screen made of carbon was investigated to control the carburizing potential within the plasma-assisted process. Laser absorption spectroscopy was used to determine the resulting process gas composition at different levels of oxygen admixture using O<sub>2</sub> and CO<sub>2</sub>, respectively, as well as the long-term trends of the concentration of major reaction products over the duration of a material treatment of ARMCO<sup>®</sup> iron. The short-term studies of the resulting process gas composition, as a function of oxygen addition to the process feed gases N<sub>2</sub> and H<sub>2,</sub> showed that a stepwise increase in oxygen addition led to the formation of oxygen-containing species, such as CO, CO<sub>2</sub>, and H<sub>2</sub>O, and to a significant decrease in the concentrations of hydrocarbons and HCN. Despite increased oxygen concentration within the process gas, no oxygen enrichment was observed in the compound layer of ARMCO<sup>®</sup> iron; however, the diffusion depth of nitrogen and carbon increased significantly. Increasing the local nitrogen concentration changed the stoichiometry of the ε-Fe<sub>3</sub>(N,C)<sub>1+x</sub> phase in the compound layer and opens up additional degrees of freedom for improved process control. |
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