Precise spectral directional infrared emissivity of a Cantor high-entropy alloy

Abstract

The multicomponent equiatomic CrMnFeCoNi alloy was proposed by B. Cantor almost 20 years ago and was the first in the family of so-called multiprincipal or high-entropy alloys (HEAs). Various mechanical properties of the Cantor alloy and its derivatives, such as corrosion behaviour, oxidation resistance, irradiation response, diffusion bonding, and weldability have been studied these past years. Unfortunately, data on their thermo-physical properties are scarce and the information about infrared emissivity is completely absent. Having reliable infrared emissivity data at working conditions is very important for non-contact temperature measurements and for modelling heat transfer by radiation during manufacturing. In this work a Cantor alloy, as a typical example of HEAs was manufactured with levitation melting in vacuum. The alloy contains mainly one phase with face-centered cubic lattice and small amount of oxide precipitates. The angle-dependent spectral directional emissivity was measured between 200 and 700 ºC. Reproducible data were obtained upon several thermal cycles. The total directional emissivity is almost constant from 10º to 50º and it increases up until it reaches a maximum around 70º. Integrating these data total hemispherical emissivity were determined and it was observed that this property remains almost constant at 0.28 in a wide temperature range, showing a minor increase with increasing temperature. Spectral directional emissivity measurements allow detecting incipient oxidation processes. These data show the necessity of measuring emissivity at working temperatures to achieve a precise quantification of radiative heat transfer.