High throughput optimization of hard and tough TiN/Ni nanocomposite coatings by reactive magnetron sputter deposition

Abstract

A combinatorial thin-film synthesis approach together with a high throughput analysis methodology was successfully applied to synthetize TiN/Ni coatings with optimum mechanical properties. The synthesis approach consists of the deposition of TiN/Ni coatings with the Ni content ranging from around 0 to 20 at.% by reactive magnetron sputtering with a well-defined composition gradient, so that almost all possible compositions are produced in one single coating under identical conditions, removing uncertainties from processing conditions. The analysis methodology continuously screened the microstructure, residual stresses, hardness and fracture toughness of TiN/Ni coatings. The results show that a nanocomposite microstructure of equiaxed nanograins of crystalline δ-TiN embedded in a Ni rich amorphous phase is formed in the composition window between 8 and 12 Ni at.%. This microstructure offers a superior combination of hardness and toughness and a simultaneous reduction of residual stresses with respect to TiN coatings grown in the same conditions. Higher Ni contents are however detrimental because they compromise the integrity of the coatings.