High Entropy Alloys: Prospective Materials for Tribo‐Corrosion Applications

Abstract

Tribo-corrosion is an issue of concern for marine and other fluid machinery. High entropy alloys (HEAs) represent a new category of materials possessing exceptional properties. We investigated the erosion-corrosion behavior of Al 0.1 CoCrFeNi HEA. For comparison, stainless steel SS316L is also evaluated. Results indicate that despite low hardness and yield strength, HEA exhibits high erosion-corrosion resistance compared to steel. The HEA also shows high pitting and passive potentials compared to steel. The superior erosioncorrosion resistance of HEA is due to high corrosion resistance, and work hardenability. The degradation mechanism investigated using SEM show ploughing as the primary material removal mode (MRM) for HEA at an oblique angle compared to micro-cutting for SS316L steel. At normal impingement, platelet mechanism is observed to be the dominant MRM.

Correlating Strength and Hardness of High‐Entropy Alloys

“… General plots of HV against a,c) tensile yield strength and b,d) ultimate tensile strength of single‐phase FCC HEAs including Al 0.1 CoCrFeNi, [ 74–79 ] Al 0.25 CoCrFeNi, [ 28 ] Al 0.3 CoCrFeMnNi, [ 80 ] Al 0.3 CoCrFeNi, [ 81–84 ] CoCrFeMnNi, [ 35–48 ] (CoCrFeMnNi) x Al 100– x , [ 47 ] Co 20 Cr 26 Fe 20 Mn 20 Ni 14 , [ 45 ] CoCrFeNi, [ 45,48,53–58 ] CoCrNi, [ 49–52 ] Co 26 Cr 18.5 Fe 18.5 Mn 18.5 Ni 18.5 , [ 45 ] CoCuFeMnNi, [ 85,86 ] CoCuFeNi, [ 87 ] CoFeMnNi, [ 85 ] FeCoCrNi, [ 45,58 ] FeMnNi, [ 85 ] and 316 stainless steels. [ 59–66 ] The referenced three‐time line is included in each image.…”

Bio‐electrochemical response to sense implant degradation

“…Orthopaedic implants are typically based on three material classes namely, metals, ceramics and polyethylene. Tribo‐corrosion predominantly affects the surfaces of metals, and ceramics to a lesser extent (Nair, Arora, Ayyagari, Mukherjee, & Grewal, 2018). Over the past century, some of the most common biomaterials implanted are metals such as stainless steel, titanium and its alloys (Ti6Al4V, TiNbZrTa) (Long & Rack, 1998), cobalt and its alloys (CoCrMo, CoNiCrMo) (Disegi, Kennedy, & Pilliar, 1999; Gurappa, 2002) and ceramics such as alumina (Al 2 O 3 ) (Kluess, Bergschmidt, Mittelmeier, & Bader, 2014), zirconia (ZrO 2 ) (Piconi & Maccauro, 1999) and silicon carbide (SiC) (Kailer et al., 2011).…”

Erosion-corrosion behaviour of CoCrFeNiMo0.85 and Al0.5CoCrFeNi complex concentrated alloys produced by laser metal deposition

“…The slurry erosion resistance of CCA Al0.1CoCrFeNi was found [17] to be superior to that of mild steel but lower than UNS S31603 stainless steel but these comparisons relate mainly to mechanical damage as the test programme was carried out in a tapwater slurry. A detailed comparison [18], of the corrosion and erosion-corrosion behaviour of a Al0.1CoCrFeNi CCA alloy and conventional UNS S31603 stainless steel in a 3.5% NaCl slurry, revealed that the material loss of the CCA alloy was slightly greater than that of the stainless steel at an impingement angle of 90° but much less at 30° impact -mainly on account of a considerable increase in material loss of the stainless steel at the oblique angle.…”

“…Although the work described in this paper [18] covered an interesting range of aspects, the paper suffers somewhat in a number of respects such as corrosion monitoring exercises not including in-situ measurements, failure to separate synergy into its two erosive and corrosive components and a misinterpretation of the role of the squeeze film in erosion-corrosion systems.…”