Laser treatments of titanium surfaces In different atmospheres for Improved adhesion properties

We present a first study on the effects of the ambient gases of a laser pre-treatment on the interface and bond strength to a thermoplastic polymer, polyetheretherketone (PEEK). The pretreatments of titanium TiAl3V2.5 surfaces were performed with a pulsed Nd:YAG laser in air, oxygen, nitrogen and argon. SEM investigations showed macro-structuring at the micron scale and superimposed fine nanostructuring. We characterized the initial and residual bond strengths by means of single-lap shear experiments prior and after degradation for 7 days in 80°C hot H2O, respectively. The initial strengths of the surfaces laser treated in air, oxygen and nitrogen were comparable at around 77 MPa, whereas for samples pretreated in Argon slightly lower strengths of 676 MPa were obtained. After degradation, the absolute strength loss varied from 11% (air) to 24% (Ar). While laser treatment in reactive gases still led to comparably high strengths (~64 MPa), the pre-treatment in Ar caused a significant loss of the residual strength (52 MPa). The shear strengths and degradation results correlated with changes in the nanostructures created by the laser irradiation, which was substantially less in case of argon compared to those obtained in reactive gases. The presence of titanium oxides was detected by EDX on all four surfaces