AbstractMany industrial processes require materials with high erosion properties, e.g. a material must be both corrosion and wear resistant. Therefore, the work presented aimed to find novel alloys with high erosion resistance in the form of High Entropy Materials while preferably utilising common, widely available elements. Furthermore, it was planned from the beginning that additional corrosion resistance might be achieved if the alloys could be produced as an amorphous material.
Vacuum arc melting was used in search of complex multielement alloys with minimal or absent phase separation. The thin film production was seen as a step to reduce the material cost of the found promising alloys and to further increase alloy mechanical properties by creating the alloy in the slight deviation from the thermodynamical equilibrium.
Electron microscopy (Scanning and Transmitting) in combination with X-Ray Diffraction was employed to get insides into crystalline arrangements. At the same time, Energy Dispersive XRay (EDX) spectroscopy allowed us to determine phase compositions.
The main finding in bulk alloys results showed that the FeCrMnNiCx (x=2 at. %) had a singlephase structure with no evidence of elemental segregation, thereby confirming that the synthesized alloy is a single-phase high entropy alloy. The results of FeCrMnNiC and FeCrSiNb high entropy thin film alloys deposited on silicon and steel substrates exhibited that the alloys are equiatomic and single-phase with no element separation or segregation. As well as the FeCrMnNiC and FeCrSiNb thin film alloys showed amorphous structure.
Both materials coated with the material samples (on silicon and steel) showed corrosion resistance exceeding one of the 304 SS in 0.6 M NaCl, H2SO4 solutions, and crude oil at standard temperature and pressure.
The novel materials also show very high hardness for metallic/metalloid composition. The exceptional properties of the alloys allow us to designate them for use in highly erosive environments.
|Date of Award
|30 Mar 2023
|Vladimir Vishnyakov (Main Supervisor) & John Allport (Co-Supervisor)