Elemental distribution in carbon-supersaturated high entropy alloycoatings: A synchrotron-based study

• The properties of high entropy alloys (HEAs) are strongly affected by the addition of carbon past the solubility limit. Despite this is the local chemistry in these meta-stable materials not well-characterized. To better understand how carbon affects the elemental distribution of alloys whose constituent elements have widely varying carbon affinities, this paper studies amorphous sputter-deposited coatings of CoCrFeMnNi with concentrations of up to 11\% carbon. Hard x-ray photoelectron spectroscopy (HAXPES), near-edge x-ray absorption fine structure (NEXAFS), and transmission electron microscopy (TEM) were used to determine how each metallic element is affected by the presence of carbon. As-deposited samples are also compared to annealed samples to study the thermal stability and the Calphad method was used to predict the thermodynamic equilibrium state. All five component metals had weak interaction with carbon, including Ni which had a less metallic character in the carbon-containing samples. While elemental segregation is expected at all temperatures at thermodynamic equilibrium, carbon did not promote segregation in the as-deposited samples. During annealing, however, the elements rearranged and formed a mixture of alloy phases and crystalline Cr-rich carbides. Rearrangement of the elements also occurred in the surface oxide, where Mn became dominant. The combination of techniques to characterize HEAs revealed promising trends for future research into these important materials.

Ämnesord

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

Nyckelord

hard x-ray photoelectron spectroscopy

synchrotron

x-ray absorption

high entropy alloy

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vet (ämneskategori)

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