High-rate deposition of AlTiN and related coatings with dense morphology by central cylindrical direct current magnetron sputtering

An industrial coating equipment, routinely used for the deposition of wear protection coatings on tools by means of vacuum arc evaporation with rotating cylindrical cathodes, has been modified for direct current (DC) reactive magnetron sputtering. We use a central cylindrical magnetron to achieve high-rate deposition of dense hard AlxTi1 − xN, AlxCr1 − xN, TiN and related coatings. With a DC power of 25 kW and one-fold rotation of the tools, the resulting deposition rate is 10 μm/h over a total area of 0.3 m2, resulting in the high throwing power of more than 3 μm·m2/h. Scanning electron microscopy studies show no columnar morphology, but instead a dense fibrous one. Investigations with transmission electron microscopy at higher resolutions revealed a fine fibrous-like (diameter of about 25 nm) and extremely dense microstructure, with the axis of the fibers oriented in the direction of the film growth. Atom probe tomography studies confirmed the dense microstructure exhibiting no change in the Al/Ti ratio across the column boundaries over an investigated length of about 200 nm. The load-invariant hardness of the Al0.57Ti0.43N coatings reached a value of 33.4 ± 1.5 GPa, and the elastic modulus amounted to 466 ± 15 GPa. The surface of the deposited coatings is very smooth with average roughness Ra = 0.06 μm and maximum roughness Rz = 0.72 μm. The coatings deposited on tools show excellent cutting performance.