Epitaxial growth of tantalum carbides by low carbon flow carburizing

Abstract

International audienceThe 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

Structure, mechanical and tribological properties, and oxidation resistance of TaC/a-C:H films deposited by high power impulse magnetron sputtering

“…Among transition metal carbides, tantalum carbide (TaC) has attracted considerable attention since it has high hardness, good thermal stability, high melting temperature (3880 • C), low contact resistance, and excellent tribological performance. Based on its superior performance and promising applications in industry, nanocomposite TaC coatings have been prepared and studied by a variety of modern surface modification technologies, such as hot pressing [17], magnetron sputtering [1] [18][19] [20][21] [22] [23], in situ reaction (ISR) technique [24] [25], carburization [26] [27], pulsed laser ablation deposition [28][29] [30], chemical vapor deposition [31] [32], electrodeposition [33] and so on. Among them, one of the most widely used techniques to grow TaC films is direct current (DC) magnetron sputtering.…”