Erosion behaviour of composite Al-Cr cathodes in cathodic arc plasmas in inert and reactive atmospheres

TL;DR

This study investigates the erosion behavior of Al-Cr composite cathodes with varying aluminum content in different atmospheres, revealing formation of intermetallic phases and non-uniform poisoning effects in reactive gases.

Contribution

It provides new insights into the erosion mechanisms and surface modifications of Al-Cr cathodes in inert and reactive atmospheres, including formation of intermetallics and effects of magnetic field configuration.

Findings

Intermetallic Al-Cr phases form in heat-affected zones.

Reactive layers are absent in the erosion zone except for oxide islands.

Poisoning effects are non-uniform due to magnetic field influence.

Abstract

Al$_{x}$Cr$_{1-x}$ composite cathodes with Al contents of x = 0.75, 0.5 and 0.25 were exposed to cathodic arc plasmas in Ar, N$_2$ and O$_2$ atmospheres and their erosion behaviour was studied. Cross-sectional analysis of the elemental distribution of the near-surface zone in the cathodes by scanning electron microscopy revealed the formation of a modified layer for all cathodes and atmospheres. Due to intermixing of Al and Cr in the heat-affected zone, intermetallic Al-Cr phases formed as evidenced by X-ray diffraction analysis. Cathode poisoning effects in the reactive N$_2$ and O$_2$ atmospheres were non-uniform as a result of the applied magnetic field configuration. With the exception of oxide islands on Al-rich cathodes, reactive layers were absent in the circular erosion zone, while nitrides and oxides formed in the less eroded centre region of the cathodes.