Abstract
The surface hardening of single-face-centred cubic (fcc)-phase CrMnFeCoNi and the manganese-free CrFeCoNi alloy was conducted using low-temperature nitrocarburisation. The microstructural investigations reveal the successful formation of a homogeneous diffusion layer with a thickness of approximately 16 µm. The interstitial solution of carbon and nitrogen causes an anisotropic lattice expansion. The increase in microhardness is in accordance to the graded concentration profile of the interstitial elements. Wear tests show a significantly enhanced resistance at different loads. The electrochemical tests reveal no deterioration in the corrosion resistance. The absence of precipitates is proven by microstructural investigations. The results prove the applicability of the concept of solution hardening by the formation of supersaturated solutions for the material group of high-entropy alloys. Hence, an increase of entropy with the consideration of lattice interstices provides new development approaches.
Highlights
In recent years, the multi-component alloy concept of high-entropy alloys (HEAs) has received considerable attention [1]
Single-phase HEAs like the CrMnFeCoNi HEA system with a face-centred-cubic structure reveal good ductility and corrosion resistance, while a sufficient wear resistance is often associated to other compositions with body-centred-cubic- or multi-phase constitution [7,8]
The two single-phase HEA-systems CrMnFeCoNi and CrFeCoNi were produced in equimolar composition using arc-melting of elemental granulates
Summary
The multi-component alloy concept of high-entropy alloys (HEAs) has received considerable attention [1]. The demands of superimposed loading require a complex profile of functional surface properties, resulting in a challenge for recent research activities in surface technology [5,6]. Single-phase HEAs like the CrMnFeCoNi HEA system with a face-centred-cubic (fcc) structure reveal good ductility and corrosion resistance, while a sufficient wear resistance is often associated to other compositions with body-centred-cubic (bcc)- or multi-phase constitution [7,8]. An improvement of the relatively poor wear resistance of single-phase HEAs requires a functional division between surface and constructive properties. In this case, surface technologies are an appropriate opportunity to adjust the surface functionality
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