Influence of Si doping and O2-flow on arc deposited (Al,Cr)2O3 coatings

TL;DR

This study investigates how silicon doping and oxygen flow influence the structure, composition, and properties of arc-deposited (Al,Cr)2O3 coatings, revealing that Si promotes metastable cubic phases and slightly reduces hardness.

Contribution

It provides new insights into the effects of Si doping and oxygen flow on the phase structure and hardness of (Al,Cr)2O3 coatings deposited by arc methods.

Findings

Si doping promotes metastable B1-like cubic structure.

Si incorporation slightly reduces coating hardness.

Oxygen flow has minimal effect on Si content.

Abstract

(Al,Cr)2O3 coatings with Al/(Al+Cr) = 0.5 or Al = 70 at.%, doped with 0, 5 or 10 at.% Si, were deposited on hard metal and Si(100) substrates to elucidate the influence of Si on the resulting coatings. The chemical analysis of the coatings showed between 3.3 and 7.4 at.% metal fraction Si incorporated into all studied coatings depending on cathode Si-composition. The incorporated Si content does not change significantly with different oxygen flow covering a wide range of deposition conditions from low to high O2 flow during growth. The addition of Si promotes the metastable B1-like cubic structure over the thermodynamically stable corundum structure. The hardness determined by nanoindentation of the as-deposited coatings is slightly reduced upon Si-incorporation as well as upon increased Al-content. Si is found enriched in droplets but can also be found at a lower content, evenly spread, without visible segregation on the ~5 nm scale, in the actual oxide coating. The positive effect of improved cathode erosion upon Si-incorporation has to be balanced against the promotion of the metastable B1-like structure, having lower room temperature hardness and inferior thermal stability compared to the corundum structure.