Pulsed enhanced electron emission is a new approach in PVD technology for the deposition of metal oxides. The process is dedicated to the formation of alumina-based and other metallic oxide layers and comprises high current pulse technology for the arc sources as well as for the substrate bias. The technology allows a deposition of hard alumina-based coatings at substrate temperatures of about 550°C and even below. Reproducibility and deposition rates were demonstrated in a production system and proved to be comparable with arc ion plating processes for standard PVD nitride coatings.

The high flexibility of the process allows an easy control of the reactive gases, smooth and abrupt transitions between the layers in multi layer structures and the combination of metals, oxides and nitrides in layer systems deposited in one single process in a batch-system. Layers of up to 15 µm thickness and above have been deposited showing an excellent adhesion. Cutting tests for inserts with respect to turning and milling show promising results compared to standard PVD layers as well as in comparison with CVD deposited layers.

A number of different oxide layers were prepared with this new technology illustrating the enormous potential for the design of layer systems in wear resistant coatings. The layers were characterized with respect to mechanical properties, film morphology, crystal structure, stoichiometry and chemical stability.

The phase formation and microstructure evolution of magnetron-sputtered coatings was examined for the Cr-Al-N-O material system. A combinatorial material science based approach by sputtering from a segmented target with a Leybold Z 550 machine was applied for the deposition experiments. The target was composed of two pieces, one made of bulk, hot pressed (Cr, Al)N and the other of a commercial Al₂O₃ plate. Both non-reactive and reactive deposition was applied. In each experiment six coatings of different composition and microstucture were obtained simultaneously by placing 6 substrate samples in individual positions below the target. The coatings, as-deposited and thermally annealed in vacuum up to 750°C, were characterized by Electron Probe Micro Analysis, X-Ray Diffraction, and Transmission Electron Microscopy. The microhardness was measured by the Vickers method.

Non-reactively as-deposited coatings exhibited a nanocrystalline structure independent of the chemical composition and moderate hardness values between 1000 and 1200 HV0.05. A strong increase in the crystallite sizes of these coatings was observed at annealing temperatures above 600°C. This crystallization was accompanied by a significant increase in the microhardness up to 1500 HV0.05 at lower Cr:Al and higher O:N concentration, and up to 2000 HV0.05 at higher Cr:Al and lower O:N concentration. The brittle, ceramic behaviour of these coatings increased clearly with increasing annealing temperature. The reactive deposition in nitrogen atmospheres resulted in the synthesis of nanocrystalline coatings with a significantly higher hardness and ductility. The Vickers microhardness of as-deposited films was in the range of 2250 to 2500 HV0.05 and no brittle cracking of the coatings was observed. Annealing in vacuum however did not result in a remarkable change of the hardness values but in a change of the crystalline structure of the coatings.