Characteristics of (Mo-Ta-W)-C and (Nb-Ta-W)-C refractory multi-principal element carbide thin films by non-reactive direct current magnetron co-sputtering

Abstract

The (Mo-Ta-W)-C and (Nb-Ta-W)-C carbide thin films were prepared by non-reactive magnetron co-sputtering. The (Mo-Ta-W)-C thin films exhibited the simple BCC structure with the strip-like surface morphologies and a double-layer structure for cross sections with a columnar upper layer and an featureless lower layer. In the (Mo-Ta-W)-C thin films, the metal-metal and metal-oxygen bonds were observed with no metal-carbon bonds. The carbon-carbon bonds were observed, indicating free carbon phases existed in the (Mo-Ta-W)-C thin films. The surface roughness of (Mo-Ta-W)-C thin films was small with Ra value of 3.11–3.74 nm. The hardness of (Mo-Ta-W)-C thin films was 32.6–33.5 GPa. The (Nb-Ta-W)-C thin films formed the amorphous structure. Different from (Mo-Ta-W)-C thin films, the metal-carbon bonds existed in the (Nb-Ta-W)-C thin films, except the metal-metal and metal-oxygen bonds. The C-C bonds were also observed, indicating free carbon phases existed in the (Nb-Ta-W)-C thin films. The surfaces of (Nb-Ta-W)-C thin films displayed a granular structure with Ra of 0.86–1.00 nm, and the cross sections exhibited a fine fibrous structure. The hardness values of (Nb-Ta-W)-C thin films ranged from 34.5 to 36.1 GPa with elastic modulus of 319.6–349.5 GPa. The corrosion current density and polarization resistance of (Nb-Ta-W)-C thin films were better than 304 stainless steel, indicating good anti-corrosive performance of (Nb-Ta-W)-C thin films. The (Nb23Ta21W23)C33 thin film had low reflectivity in the visible light band (300–800 nm), and high reflectivity in the near-infrared band (800–2500 nm), with the solar absorption ratio αs of 0.4577 and the infrared emissivity εH of 0.178.