Microstructure and corrosion resistance of high entropy alloy (AlNiCoCrFe) coatings prepared by TIG process

Corrosion resistance, hardness and other mechanical properties of high entropy alloys are enhanced due to the addition of the proper elements. In this study, an equimolar powder mixture of AlNiCoCrFe was prepared as a coating material on plain carbon steel. It was produced by gas tungsten arc welding with the electrical currents of 90, 110 and 130 A. Experimental results demonstrated that at the electrical current of 110 A, the AlNiCoCrFe layer contained two-phase structures of BCC and FCC. The layer exhibited improved hardness from about 180 to 650 HVN. The potentiodynamic polarisation and electrochemical impedance spectroscopy of the AlNiCoCrFe alloys, obtained in 1M HCl solutions, showed that corrosion resistance of steel substrate could be considerably improved by preparing an AlNiCoCrFe coating on its surface. Polarisation resistance increased from 62.5 to 834 Ωcm². Furthermore, electrochemical measurements revealed that optimum corrosion resistance were obtained at 110 A electrical current.