Evaluation of bias voltage-dependent mechanical properties of amorphous TiSi2 thin films on PEEK by nano-characterization techniques

Thin films on PEEK have been designing by magnetron sputtering, using bias voltages ranging from −31 to −157 V. The X-ray diffraction and EDX show how the amorphous films resulting have an elemental composition very close to the stoichiometry TiSi. The AFM and SEM performed on top and cross-section, respectively, of film reveal a smooth and uniform surface, free of pores and cracks, and a compact microstructure. The evaluation of the resolved shear stress, yield strength, hardness, scratch resistance, and fracture toughness show how these values increase in the TiSi/PEEK system as the bias voltage increase. The development of these hard and tough thin films has enabled the fracture toughness achieved by the TiSi/PEEK system increase when a bias voltage equal to or higher than −108 V is used during the deposition process. For these bias conditions, the compressive residual stresses generated are large enough to prevent crack nucleation. The increase of the crack resistance gives as a result that K reaches values above 32 MPa*m. This value is much greater than those values corresponding to the classic ceramic coatings, such as AlO (4.6 MPa*m) and ZrO (7.6 MPa*m).