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Progress in Plasma Processing of Materials, 2001

ISBN:
1-56700-165-3 (Print)

TITANIUM POWDER NITRIDATION BY REACTIVE PLASMA SPRAYING

C. Ponticaud
SPCTS UMR-CNRS 6638, 123 Avenue A. Thomas 87060 Limoges, France

Alain Grimaud
L.E.T.P., Faculté des Sciences, 2 Bd Lavoisier 49045 Angers Cedex, France

Alain Denoirjean
Equipe Plasma Laser Matériaux, ESA CNRS 6015, 87060 Limoges Cedex, France

Pierre Lefort
Laboratoire Science des Precedes Ceramiques et Traitements de Surface UMR CNRS 6638 123 Avenue Albert-Thomas F-87060 Limoges Cedex, France

Pierre Fauchais
Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface UMR CNRS 6638 University of Limoges 123 avenue Albert Thomas, 87060 LIMOGES - France

Abstract

Titanium powder has been sprayed with nitrogen or Ar/H2 d.c. plasma jets flowing in air. Particles have been collected at several distances downstream of the nozzle exit. In the first 40-50 mm, convective movements created within the droplets entrain homogeneously nitrogen and oxygen in the particle cores. Farther downstream, convection is less important and absorption of nitrogen and oxygen is controlled by diffusion from the particles surface. After solidification induced by high quenching rates (in the order of 105 K/s) due to different cooling means, particles are composed by a superficial layer which is an oxi-nitride of titanium and in their core by a solid solution α-Ti containing both nitrogen and oxygen.