Plasma Characteristics of Supersonic Nitrogen/Hydrogen-Mixture and Ammonia Plasma Jets and Nitrided Material Properties

Abstract:

Spectroscopic and electrostatic probe measurements were made to examine plasma characteristics under nitriding for a 10-kW-class direct-current arc plasma jet generator with a supersonic expansion nozzle in a low pressure environment. Heat fluxes into the plate from the plasma were also evaluated. Ammonia and mixtures of nitrogen and hydrogen were used as the working gas. The H-atom electronic excitation temperature and the N₂ molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. As approaching the titanium plate, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one. Both the electron number density near the plate and the heat flux increased with H₂ mole fraction for mixtures gases. In cases with mixtures of N₂ and H₂, a radical of NH with a radially wide distribution is considered to contribute to the better nitriding as a chemically active and non heating process.

• Periodical: Materials Science Forum (Volumes 449-452)
• Pages: 373-376
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.449-452.373
• Online since: March 2004
• Authors: Hirokazu Tahara, Yasutaka Ando, Takao Yoshikawa
• Keywords: Ammonia, Mixture of Nitrogen and Hydrogen, Nitriding, Plasma Processing, Supersonic Flow, Surface Treatment, Thermodynamical Nonequilibrium Flow

References

[1] F. Gitzhofer et al.: Proc. 15th Int. Thermal Spray Conf., 2 (1998) 1283.

[2] K. Mailhot et al.: Proc. 15th Int. Thermal Spray Conf., 2 (1998) 1419.

[3] H. Tahara et al.: Proc. Int. Symp. Designing, Processing and Properties of Advanced Engineering Materials, 1997, p.523.

[4] Y. Andoh et al.: Proc. United Thermal Spray Conf., 1999, p.234.

[5] H. Tahara et al.: IEEE Trans. Plasma Sci., 24 (1996) 218.

[6] H. Tahara et al.: IEEE Trans. Plasma Sci., 26 (1998) 1307.

[7] H. Tahara et al.: Proc. United Thermal Spray Conf., 1999, p.720.

[8] H. Tahara et al.: Proc. 1st Int. Thermal Spray Conf., 2000, p.21.