Coated tools constitute the majority of the tools applied in material removal processes, rendering the employment of uncoated ones as an exception. A broad growing market of coated cutting tools has been developed. Moreover, numerous material- and manufacturing-engineers have joint their expertise, aiming at developing coatings meeting the needs for processing the most difficult-to-cut materials at the most extreme cutting conditions. The emerging of new workpiece, tool and film materials, the evolution of sophisticated coatings’ characterization methods and the continuous need for higher productivity rates, maintain vivid the industrial and scientific interest for further advancing this field.

Cutting with coated tools: Coating technologies, characterization methods and performance optimization

Plasma technology has been widely applied in the ozone production, material modification, gas/water cleaning, etc. Various nanomaterials were produced by thermal plasma technology. However, the high temperature process and low uniformity products limit their application for the high value added chemicals synthesis, for example the functional materials or the temperature sensitive materials. Microplasma has attracted significant attentions from various fields owing to its unique characteristics, like the high-pressure operation, non-equilibrium chemistry, continuous-flow, microscale geometry and self-organization phenomenon. Its application on the functional nanomaterial synthesis was elaborately discussed in this review paper. Firstly, the main physical parameters were reviewed, which include the electron temperature, electron energy distribution function, electron density and the gas temperature. Then four representative microplasma configurations were categorized, and the proper selection of configuration was summarized in light of different conditions. Finally the synthesis, mechanism and application of some typical nanomaterials were introduced.

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Microplasma: A New Generation of Technology for Functional Nanomaterial Synthesis

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

α-Al2O3 coatings with (1012), (1014), (0001) and (1010) textures were obtained using chemical vapour deposition. The textured coatings were compared with α-Al2O3 obtained through the κ→α phase transformation. The coating microstructures were studied by scanning electron microscopy and transmission electron microscopy and residual stress and texture were determined by X-ray diffraction using Cr Kα and Cu Kα radiation, respectively. Microtexture was investigated using electron back-scatter diffraction. Wear properties of the α-Al2O3 coatings were evaluated in turning of cast iron and steel. All the studied coatings were under a tensile stress of the order of 0.2–0.7 GPa. The cutting tests confirmed substantial texture effects especially in cutting of steel. The best performance was exhibited by the (0001) textured coatings i.e. when the basal planes of α-Al2O3 grains were nearly parallel to the coating surface. As compared with the other textured coatings, the (0001) textured coating showed a clearly enhanced ability to undergo uniform plastic deformation. The present work also established that the texture of α-Al2O3 coatings could be controlled by process data during deposition.

Enhanced performance of α-Al2O3 coatings by control of crystal orientation

α-alumina coatings have been deposited directly onto cemented-carbide and Mo substrates at a temperature as low as 650 °C using reactive high-power impulse magnetron sputtering (HiPIMS) of Al in an ...

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Synthesis of α-Al2O3 thin films using reactive high-power impulse magnetron sputtering

The influence of nucleation on the microstructure and properties of CVD Al2O3 was investigated. The experimental α-Al2O3 layers were deposited (a) without nucleation control and (b) with nucleation steps resulting in pronounced 〈101¯2〉, 〈101¯4〉 and 〈101¯0〉 growth textures. The experimental layers were characterised using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Wear properties of the textured coatings were evaluated in turning. The chemistry of the nucleation surface appeared to be an important factor in pre-determining the phase content and growth textures of the Al2O3 layers. Optimised nucleation resulted in substantially improved wear properties and these kinds of α-Al2O3 layers were typically composed of relatively small, defect-free grains exhibiting no porosity. The 〈101¯4〉 textured α-Al2O3 layer showed the best wear resistance.

S. Ruppi

Papers

Deposition, microstructure and properties of texture-controlled CVD α-Al2O3 coatings