Mechanical and tribological behaviors of hard and tough TaxHf1-xN films with various Ta contents

The hardness and toughness of HfN films alloying with Ta element is crucial for their wear resistance when they are applied in the harsh environment. In this study, TaxHf1-xN (x= 0-1) thin films with various Ta contents were deposited on silicon wafer and TC4 alloy substrates by DC reactive magnetron sputtering, respectively. The relationship between structure, mechanical and tribological properties of TaxHf1-xN films was investigated. TaxHf1-xN films are presented as the solid solutions with B1-NaCl rock salt structure. As the content of tantalum increases, the grain size and residual compressive stress of TaxHf1-xN films increases firstly then decreases, while the preferred orientation transfers from (111) to (200) and then back to (111). The hardness and H/E increases initially and then decreases with the Ta contents, which is also consistent with the fracture toughness. When x is 0.58, TaxHf1-xN film shows the maximum hardness value (44 GPa), H/E (0.15), H-3/E-2 (1.02 GPa), fracture toughness (3.48 MPa.m(1/2)) and lower wear rate (5.6x10(-6)mm(3)/Nm). It is found that the wear resistance of TaxHf1-xN films is directly related to the H/E and fracture toughness.