High power pulsed magnetron sputtering (HPPMS) is an emerging technology that has gained substantial interest among academics and industrials alike. HPPMS, also known as HIPIMS (high power impulse ...

High power pulsed magnetron sputtering: A review on scientific and engineering state of the art

Stability of W-Al2O3 cermet based solar coating for receiver tube operating at high temperature

Al2O3 has a high potential as a hard compound for wear and corrosion protection because of its chemical inertness, high corrosion resistance and hardness. This work focuses on the influence of ion bombardment on the thermal stability of sputtered Al2O3 films. An industrial scale sputter system equipped with bipolar pulsed magnetrons was used to grow coatings at 640 °C in an argon-/oxygen atmosphere under different ion bombardment conditions. To evaluate the thermal stability, heat treatments were done in vacuum combined with differential scanning calorimetry. The crystal structure was examined by X-ray diffraction and nanoindentation was used to determine coating hardness. The structure of the coatings grown on silicon substrates is either predominantly X-ray amorphous for low ion bombardment conditions or γ-Al2O3 structured for enhanced ion bombardment. For iron substrates, the formation of γ-Al2O3 is fostered. Two different transformation sequences were found, both ending in the formation of the thermodynamically stable α-Al2O3. While the γ to α-transformation on coatings deposited on iron foil occurs via the transition phase δ-Al2O3, coatings deposited on silicon transform directly into α-Al2O3. The amorphous coatings transform at lower temperatures than the coatings with γ-Al2O3 structure in the as deposited state. Hardness values of 10 GPa for the amorphous coating, 14 GPa for γ-Al2O3 and 22 GPa for α-Al2O3 were measured.

Thermal stability of sputtered Al2O3 coatings

Pulse enhanced electron emission (P3e (TM)) 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 technique for the arc sources. The method allows a deposition of hard alumina-based coatings at substrate temperatures below 600 degrees C. Different oxide layers and layer combinations were prepared with this new technique illustrating the enormous potential for the design of wear resistant coatings. The layers were characterized with respect to hardness, stress, composition, crystal structure, and thermal stability. Solid solutions of (Al1-xCrx)(2)O-3 could be synthesized for a composition range of 0.3 <= 5x<l. The growth of the solid solutions has also been demonstrated at TiCN and TiAlN interfaces. (c) 2007 Elsevier B.V. All rights reserved.

Pulse enhanced electron emission (P3e™) arc evaporation and the synthesis of wear resistant Al–Cr–O coatings in corundum structure

Thermal stability of alumina thin films containing γ-Al2O3 phase prepared by reactive magnetron sputtering

Alumina coatings were reactively deposited on steel substrates by pulsed magnetron sputtering at substrate temperatures (Ts) of 330–760 °C. Investigations into the structure and morphology of the layers were made via XRD and SEM techniques, respectively. As to the layer properties, the hardness was determined by nanoindentation, and the residual stresses were derived from the bending of the coated substrates. At substrate temperatures of less than 330 °C the Al2O3 layers are amorphous to X-rays, whereas γ-Al2O3 is detected at a substrate temperature Ts ≈ 480 °C. A further increase in substrate temperature to 560 °C results in the formation of a pronounced texture of γ-Al2O3. A phase mixture of textured γ- and α-Al2O3 is deposited at Ts ≈ 690 °C. At Ts ≈ 760 °C the layer consists completely of α-Al2O3 with crystallite sizes of about 1 μm. The occurrence of the crystalline γ phase at 480 °C is linked with a pronounced increase in hardness from 10 to 19 GPa. The layer hardness of pure α-Al2O3 amounts to 22 GPa and corresponds to the hardness of the bulk material.

G. Hoetzsch

Papers

Effect of the substrate temperature on the structure and properties of Al2O3 layers reactively deposited by pulsed magnetron sputtering