Wear-resistance, lubricity, and adhesion of femtosecond pulsed laser deposited AlMgB14-based thin films

Abstract

Ultrahard, wear-resistant coatings of thin-film AlMgB14 coatings could extend the service life of wear-prone components such as cutting tools and hydraulic pump vanes. Previous work with AlMgB14 has shown that it can have a hardness up to 46 GPa if alloyed with TiB2, and it can be coated as a thin film using pulsed laser deposition (PLD). These films have already shown promise in various industrial applications. Vane blades coated with AlMgB14 films via magnetron sputtering have significantly reduced the wear rate of the pump blades. Some research has been done on production of these films using nanosecond laser PLD, but this project was the first to use femtosecond pulsed laser deposition of coatings. In this work, research was conducted into methods to optimize the thin films’ wear resistance and lubricity. The addition of 70wt%TiB2 and/or a titanium interlayer was investigated to improve three parameters: wear-resistance, the steady-state coefficient of friction, and adhesion. The addition of TiB2 lowered the adhesion and increased the wear rate of the film. However, the films with the TiB2 addition did decrease the run-in time it took for the films to reach a steady-state coefficient of friction value. Films produced with a titanium interlayer were found to adhere to the M2 steel substrate better than films without the interlayer. The adhesion of the thin films to M2 tool steel substrates, assessed using the Rockwell C indentation adhesion test, was found to be substantially improved by the deposition of a titanium interlayer. The addition of the interlayer also lowered the steady-state coefficient of friction of the films. Ultimately, it was concluded that the film with the best properties was the pure AlMgB14 deposited for 20 minutes with a Ti interlayer.