The impressive improvement of CoCrFeMnNi high entropy alloy mechanical properties and pitting corrosion resistance by incorporation of carbon nanotube reinforcement

Abstract

CoCrFeMnNi high entropy alloy without carbon nanotube (referred to as HEA) and with 0.2 wt% CNT (called HEA + CNT) were successfully synthesized through mechanical alloying and subsequent spark plasma sintering. The samples' phase composition, microstructure, mechanical properties, and corrosion performance were investigated. XRD results showed that the addition of CNT leads to a decrease in crystallite size, reducing it from 209 nm in HEA to 190 nm in HEA + CNT. FESEM results revealed a relatively uniform distribution of smaller carbide phases in the structure of HEA + CNT sample. The addition of CNT increased the ultimate compressive stress (UCS) from 1850 MPa for HEA to 2510 MPa for HEA + CNT. Cyclic polarization results demonstrated higher pitting corrosion resistance in HEA + CNT nanocomposite, where the pitting potentials for HEA and HEA + CNT were equal to 0.127 and 0.201 V vs. SCE, respectively. The CNT addition promoted the repassivation process of the pits in HEA + CNT sample.