1. Spectroscopic study of plasma nitrocarburizing processes with an industrial-scale carbon active screen.
- Author
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Puth, A, Kusýn, L, Pipa, A V, Burlacov, I, Dalke, A, Hamann, S, van Helden, J H, Biermann, H, and Röpcke, J
- Subjects
QUANTUM cascade lasers ,INFRARED lasers ,PLASMA materials processing ,TEMPERATURE distribution ,SEMICONDUCTOR lasers ,GAS flow ,CHEMICAL processes - Abstract
The active screen plasma nitrocarburizing technology is an improvement of conventional plasma nitrocarburizing by providing a homogeneous temperature distribution within the workload and reducing soot formation. In this study, an industrial-scale active screen (AS) made of carbon-fibre-reinforced carbon serves as the cathode as well as the carbon source for the plasma-chemical processes taking place. The pulsed dc discharge was maintained at a few mbar of pressure while simultaneously being fed with a mixed gas flow of hydrogen and nitrogen ranging from 10 to 100 slh. Using in situ infrared laser absorption spectroscopy with lead salt tuneable diode lasers and external-cavity quantum cascade lasers, the temperatures and concentrations of HCN, NH
3 , CH4 , C2 H2 , and CO have been monitored as a function of pressure and total gas flow. To simulate industrial treatment conditions the temperature of the sample workload in the centre of the reactor volume was kept at 773 K by varying the plasma power at the AS between 6 and 8.5 kW. The resulting spectroscopically measured temperatures in the plasma agreed well with this value. Concentrations of the various species ranged from 6 × 1013 to 1 × 1016 cm−3 with HCN being the most abundant species. [ABSTRACT FROM AUTHOR]- Published
- 2020
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