Investigating the influence of B, C, and N on the tribo-mechanical properties of the chemically complex TiSiBCN thin films using design of experiments

Abstract

TiSiBCN thin films show promising properties like high hardness and improved tribological behavior. Adjusting the chemical composition can tailor the properties of these thin films. To investigate this influence, usually one element is varied. However, the interplay and influence of especially the light elements B, C, and N on the tribo-mechanical properties of chemical complex TiSiBCN thin films remain unclear. Therefore, a design of experiment using a central composite design (CCD) was employed to investigate the influences of these light elements on the tribo-mechanical properties of TiSiBCN thin films. TiSiBCN with varying chemical compositions were grown in a magnetron sputtering process by adjusting the cathode power of TiB2/TiSi2 composite targets and the gas flow rates of C2H2 and N2. X-ray diffraction (XRD) analysis revealed crystalline phases based on Ti, TiN, TiC, and TiB, with varying degrees of crystallinity dependent on the chemical composition, where the TiSiBCN thin films demonstrate a broad spectrum of mechanical properties, with hardness and elastic modulus ranging from 20.2 to 39.7 GPa and from 222.3 to 405.0 GPa, respectively. Notably, the B content significantly affects the mechanical properties, with the highest hardness and elastic modulus observed at 46.0 at.-% B. In tribometer tests against an Al2O3 ball under dry friction at room temperature, the TiSiBCN thin films also exhibit a broad spectrum of tribological properties, with the coefficients of friction (CoF) between 0.62 and 0.89 and wear rates between 6.4 × 10−5 and 12.2 × 10−5 mm3/Nm. The lowest CoF of 0.62 with a wear rate of 7.7 × 10−5 mm3/Nm is obtained for TiSiBCN with high amounts of 31.1 at.-% C and 33.5 at.-% N, while high 31.7 at.-% C and low 11.2 at.-% N contents favor the lowest wear rate of 6.4 × 10−5 mm3/Nm with a CoF of 0.74. The tribological results reveal the significant influence of C and N on friction and wear, with TiSiBCN displaying reduced friction and wear tending to have lower hardness. Consequently, TiSiBCN thin films with either high hardness or enhanced friction and wear performance are attainable by adjusting the chemical composition. Depending on the application requirements, the content of the light elements is decisive for the properties of TiSiBCN thin films. The CCD provides insights into the intricate interplay between the chemical composition and tribo-mechanical performance of TiSiBCN. Adjusting the concentrations of B, C, and N within TiSiBCN is crucial for tailoring the tribo-mechanical behavior to meet the specific requirements of applications.