Improvement ductility and corrosion resistance of CoCrFeNi and AlCoCrFeNi HEAs by electroless copper technique

In this study, the effect of copper coated particles on the properties of CoCrFeNi and AlCoCrFeNi high entropy alloys (HEAs) was studied. Mechanical milling is applied to achieve a good homogeneous distribution of an equiatomic CoCrFeNi and AlCoCrFeNi HEAs for 25 h milling time, followed by an electroless copper plating with 5-20 wt.% Cu by 5 wt.%, have been established. The prepared powder alloys were compacted at 800 MPa, then sintered at 1150 degrees C, 1200 degrees C, 1250 degrees C for Cu-x/(CoCrFeNi)(1-x) HEA and 900 degrees C, 950 degrees C, and 1000 degrees C for Cu-x/(AlCoCrFeNi)(1-x) HEA in a vacuum furnace for 90 min. The correlation between the microstructure, density, hardness, wear behavior and corrosion resistance of the fabricated CoCrFeNi, Cu-x/(CoCrFeNi)(1-x) and Cu-x/(AlCoCrFeNi)(1-x) HEAs were investigated. The results revealed that, alloys which sintered at 1200 degrees C for (CoCrFeNi - Cu-x/(CoCrFeNi)(1-x) HEAs) and at 950 degrees C for (Cu-x/(AlCoCrFeNi)(1-x) HEA) exhibit the highest relative density. Densification was enhanced as a result of increasing the nano Cu wt.% content. A dramatic decrease in the produced samples' hardness was observed where it decreased from 189.1 HV to 134.5 HV for Cu-x/(CoCrFeNi)(1-x) and from 403 HV to 191 HV for Cu-x/(AlCoCrFeNi)(1-x) HEAs by the addition of the nano Cu wt.% content. In addition, Wear rate is increased gradually by the addition of the nano Cu wt.% content. The electrochemical results indicate that an increased nano Cu wt.% content corresponds to an increased corrosion rate from 0.297 mm/year to 1.84 mm/year for Cu-x/(CoCrFeNi)(1-x) and from 0.03 mm/year to 0.093 mm/year for Cu-x/(AlCoCrFeNi)(1-x) HEAs. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

In this study, the effect of copper coated particles on the properties of CoCrFeNi and AlCoCrFeNi high entropy alloys was investigated. The results showed that an increase in nano copper content led to higher density and wear rate, while hardness and corrosion resistance decreased gradually.