New coating method cuts energy use in protective film production
Researchers have developed a way to grow dense titanium boride coatings—used to protect cutting tools—without heating substrates, reducing energy consumption during manufacturing. The technique uses ion bombardment instead of heat, offering manufacturers a path to lower production costs while meeting sustainability goals.
Originaltitel: W-ion irradiation promotes dense TiB<sub>x</sub> film growth during magnetron sputtering without substrate heating
<p>Lowering energy consumption during thin film growth by magnetron sputtering techniques is essential for future industry as a step towards reaching the United Nations (UN) sustainable development goals. Large potential for energy savings has been shown by employing high-mass metal ion irradiation from targets operated in highpower impulse magnetron sputtering (HiPIMS) mode. With this approach, demonstrated for transition metal (TM) nitrides, thermally-induced adatom mobility is replaced with that supplied by overlapping collisions cascades of low-energy recoils, resulting in a strong reduction of the necessary external heating. Here, the novel method is tested for TiB<sub>x</sub>, which is a model system for TM-based diborides, another class of promising materials to be used as protective coatings for cutting tools. We show that such films grown with no external substrate heating develop porosity over a wide range of B/Ti ratios. However, (Ti<sub>1-y</sub>W<sub>y</sub>)B<sub>x</sub> films grown by the hybrid W<sub>2</sub>B<sub>5</sub>-HiPIMS/Ti-TiB<sub>2</sub>-DCMS co-sputtering with substrate bias synchronized to W<sup>+</sup>/W<sup>2+</sup>-rich ion fluxes, are dense (without porosity), irrespective of x. Nanoindentation hardness increases from ∼20 GPa for TiB<sub>x</sub> to ∼40 GPa for (Ti<sub>1-y</sub>W<sub>y</sub>)B<sub>x</sub>. The slightly understoichiometric (Ti<sub>0.86</sub>W<sub>0.14</sub>)B<sub>1.91</sub> film exhibits super-hardness and is nearly stress-free. These results prove that selected heavy ion irradiation is beneficial for low-temperature growth of hard diboride films, which demonstrates the versatility of this approach and calls for evaluation in other material systems.</p>