Epitaxial growth of tantalum carbides by low carbon flow carburizing

Dominique Cotton (1, 2, 3) , Philippe Jacquet (3, 4) , Sébastien Faure (2) , Vincent Vignal (1)

1 ICB - Laboratoire Interdisciplinaire Carnot de Bourgogne
2 DAM/VALDUC - VALDUC
3 ECAM Lyon - ECAM Lyon
4 LABOMAP - Laboratoire Bourguignon des Matériaux et Procédés

The carburizing of tantalum samples under different carbon flow rates has highlighted the influence of the carbon flow rate on the structure of tantalum carbides. XRD analyses enabled the identification of surface structures that were revealed by optical micrographs. Four carbon flow rates were tested. The lowest carbon flow rate produced a Ta2C layer that grew epitaxially on the tantalum substrate according to the relationship: {View the MathML source101¯}Ta// View the MathML source{1¯101}Ta2C; View the MathML source〈101¯〉Ta// View the MathML source〈17¯17010〉Ta2C. An increase in the carbon flow rate resulted in the appearance of TaC nuclei through the carbon enrichment of the Ta2C layer. These nuclei appeared in the form of islets and highly oriented needles. EBSD (Electron Back Scattered Diffraction) analyses and pole figures revealed that the carbide layers grew epitaxially towards their substrates. The Ta2C layer grew according to the relationship View the MathML source{101¯}Ta// View the MathML source{1¯101}Ta2C while the TaC structures nucleated according to the following relationships: {111}TaC//{0001}Ta2C; 〈111〉TaC//〈0001〉Ta2C; {100}TaC// View the MathML source{202¯3}Ta2C; 〈100〉TaC// View the MathML source〈909¯8〉Ta2C and {110}TaC// View the MathML source{101¯3}Ta2C; 〈110〉TaC// View the MathML source〈909¯16〉Ta2C. The highest carbon flow produced stoichiometric TaC grains at the surface, which appeared to be equiaxed. The diversity of the TaC crystallographic orientations stems from the underlying Ta2C layer, the TaC grains having nucleated epitaxially from the Ta2C layer. This misorientation of the Ta2C grains with respect to Ta is governed by the exceeding of a carbon flow limit.

Mots clés: Epitaxial growth; Electron diffraction; Carbides; Multilayers; Coatings; Diffusion

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Matériaux

Dominique Cotton, Philippe Jacquet, Sébastien Faure, Vincent Vignal. Epitaxial growth of tantalum carbides by low carbon flow carburizing. Materials Chemistry and Physics, 2017, 192, pp.170-180. ⟨10.1016/j.matchemphys.2016.12.063⟩. ⟨hal-01484824⟩