Cathodic arc deposition of (Al,Cr)2O3: Macroparticles and cathode surface modifications

Pohler, Markus; Franz, Robert; Ramm, J.; Polcik, P.; Mitterer, Christian

doi:10.1016/j.surfcoat.2011.09.028

Cited by 79 publications

(33 citation statements)

References 29 publications

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“…Moreover, generation of two types of droplets with district differences have been observed when arcing from an Al0.7Cr0.3 compound cathode in an O2 atmosphere. 7 In the present work, we show that even for a relatively high decomposition/melting point material such as tungsten carbide (~ 3100 K), arcing is accompanied by intensive generation of macroparticles. Through visual observation of the cathode surface during and after arcing, and by close examination of the generated macroparticles, a new mechanism for macroparticle generation is suggested.…”

Section: Introductionmentioning

confidence: 50%

Macroparticle generation in DC arc discharge from a WC cathode

Zhirkov

Polcik

Kolozsvári

et al. 2017

Journal of Applied Physics

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We have studied macroparticle generation from a tungsten carbide (WC) cathode used in a dc vacuum arc discharge. Despite a relatively high decomposition/melting point (~ 3100 K), there is an intensive generation of visible particles with sizes in the range 20-35 µm. Visual observations during the discharge and scanning electron microscopy of the cathode surface as well as of collected macroparticles indicate a new mechanism for particle formation and acceleration. Based on the W-C phase diagram there is an intensive sublimation of carbon from the melt resulting from the cathode spot. The sublimation supports the formation of a sphere, which is accelerated upon an explosion initiated by Joule heating at the critical contact area between the sphere and the cathode body. The explosive nature of the particle acceleration is confirmed by surface features resembling the remains of a splash on the droplet surface.a Corresponding author: igozh@ifm.liu.se, phone +46 730 52 10 12, fax +46 13 137568 2

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Section: Introductionmentioning

confidence: 50%

Macroparticle generation in DC arc discharge from a WC cathode

Zhirkov

Polcik

Kolozsvári

et al. 2017

Journal of Applied Physics

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“…Apart from these smaller particles, also larger spherical and flat-shaped droplets are incorporated into the coatings [16]. These, however, mostly lead to nucleation of finecrystalline cubic structures.…”

Section: Resultsmentioning

confidence: 99%

Triggering the Phase Evolution Within (Al,Cr)2O3-based Coatings by Alloying and Microstructural Concepts

Koller

Hahn

Widrig

et al. 2016

Berg Huettenmaenn Monatsh

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Abstract:The synthesis of (Al,Cr)2O3 coatings by PVD frequently results in metastable cubic structures next to the thermodynamically stable and mechanically favourable hexagonal corundum phase. By alloying small amounts of Fe to powder-metallurgically produced Al0.7Cr0.3 targets -used to synthesise (Al,Cr)2O3 films by cathodic arc evaporation -a considerable increase of the hexagonal phase fraction is observed. Detailed transmission electron microscopy studies show that the growth of hexagonal crystallites of a solid solution (Al,Cr,Fe)2O3 can be triggered by small Cr-and Fe-enriched spherical particles, so-called droplets. In contrast, larger spherical or flat-shaped Alrich droplets induce re-nucleation of undesired cubic film growth. Extending these studies to additional (Al,Cr)2O3 coating systems revealed similar mechanisms, albeit by far less frequent than in the case of Fe-alloyed films. Modifications of the chemical composition of the target by small amounts of dopants may reduce droplet generation and contribute to controlled coating nucleation. Therefore, the cathode surface used is compared with particles, intentionally selected from the plasma stream. Keywords

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“…29 -32 Based on this background, arcing from Al-Cr containing cathodes in an oxygen atmosphere is of high technological importance. However, the process can result in formation of Al-rich oxide islands on the cathode surface, and formation of metallic droplets in the coating, 10,22,33,34 which may limit the cathode utilization, and influence the coating properties. However, for an isotropic plasma expansion, the average coating composition matches the virgin cathode composition even when having oxide islands on the cathode.…”

Section: Introductionmentioning

confidence: 99%

“…However, for an isotropic plasma expansion, the average coating composition matches the virgin cathode composition even when having oxide islands on the cathode. 34,35 Cathode contaminations in reactive arc processes typically include three main phenomena: 1) A change in melting point and cohesive energy of the contaminated surface layer. This may lead to altered properties of the material flux from the cathode.…”

Section: Introductionmentioning

confidence: 99%

Effect of Si on DC arc plasma generation from Al-Cr and Al-Cr-Si cathodes used in oxygen

Zhirkov

Landälv

Göthelid

et al. 2017

Journal of Applied Physics

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Al2O3 alloyed with Cr is an important material for the tooling industry. It can be synthesized from an arc discharge using Al-Cr cathodes in an oxygen atmosphere. Due to formation of Al-rich oxide islands on the cathode surface, the arc process stability is highly sensitive to the oxygen pressure. For improved stability, the use of Al0.70Cr0.25Si0.05 cathodes has previously been suggested, where Si may reduce island formation. Here, we have investigated the effect of Si by comparing plasma generation and thin film deposition from Al0.7Cr0.3 and Al0.7Cr0.25Si0.05 cathodes. Plasma ion composition, ion energies, ion charge states, neutral species, droplet formation and film composition have been characterized at different O2 flow rate for arc currents of 60 and 90 A. Si and related compounds are detected in plasma ions and in plasma neutrals. Scanning electron microscopy and energy dispersive X-ray analysis show that the cathode composition and the film composition are the same, with Si present in droplets as well. The effect of Si on the process stability, ion energies, and ion charge states is found to be negligible compared to that of the arc current. The latter is identified as the most relevant parameter for tuning the properties of the reactive discharge. The present work increases the fundamental a Corresponding author: igozh@ifm.liu.se, phone +46 730 52 10 12, fax +46 13 137568 2 understanding of plasma generation in a reactive atmosphere, and provides input for the choice of cathode composition and process parameters in reactive DC arc synthesis.

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Cathodic arc deposition of (Al,Cr)2O3: Macroparticles and cathode surface modifications

Cited by 79 publications

References 29 publications

Macroparticle generation in DC arc discharge from a WC cathode

Macroparticle generation in DC arc discharge from a WC cathode

Triggering the Phase Evolution Within (Al,Cr)2O3-based Coatings by Alloying and Microstructural Concepts

Effect of Si on DC arc plasma generation from Al-Cr and Al-Cr-Si cathodes used in oxygen

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