Effect of Hf on the microstructure, mechanical properties, and oxidation behavior of sputtered CrAlN films

Research paper by Wolfgang Tillmann, Nelson Filipe Lopes Dias; Dominic Stangier

Indexed on: 01 Jun '18Published on: 28 May '18Published in: Vacuum


Publication date: August 2018 Source:Vacuum, Volume 154 Author(s): Wolfgang Tillmann, Nelson Filipe Lopes Dias, Dominic Stangier Al-rich CrAlN films with a varying Hf content between 0 and 11.6 at.-% were synthetized by dc magnetron sputtering. The structural changes in the morphology and topography caused by Hf were evaluated by scanning electron microscopy. In addition, the phase composition of the Hf-alloyed CrAlN films was determined utilizing X-ray diffraction. The hardness and indentation modulus were determined using nanoindentation. In order to evaluate the effect of Hf on the oxidation behavior, the films were tempered in ambient air at 800 °C and subsequently analyzed. The incorporation of Hf leads to a morphological change from a fully-dense structure with small columns to a structure with more pronounced columns, which are visible as larger column tops on the surface. The Al-rich CrAlHfN films consist of the Wurtzite structure of AlN. A hardness decrease from 22.2 to 18.6 GPa is observed with an increasing Hf content and ascribed to the structural changes. When exposed to higher temperatures, the Hf-alloyed CrAlN films form an oxide layer, whose thickness is affected by the Hf content. An improved oxidation resistance is already achieved by a small amount of 2.0 at.-% of Hf. Graphical abstract