Corrosion Resistance of AlxCoCrFeNiM (M = Ti, V, Si, Mn, Cu) High Entropy Alloys in NaCl and H2SO4 Solutions

Corrosion Resistance of Al0.5CoCrFeNiCuxAgy (x = 0.25, 0.5; y = 0, 0.1) High-Entropy Alloys in 0.5M H2SO4 Solution

The electrochemical behavior of the as-cast Al_0.5CoCrFeNiCu_xAg_y (x = 0.25, 0.5; y = 0, 0.1) high-entropy alloys (HEAs) in a 0.5M H₂SO₄ solution was studied. Polarization measurements were carried out in a standard three-electrode electrochemical cell at room temperature using a platinum counter electrode and a saturated silver chloride reference electrode. For Al_0.5CoCrFeNiCu_0.5 and Al_0.5CoCrFeNiCu_0.5Ag_0.1, copper segregation along the grain boundaries was observed, which highly dissolved in the sulfuric acid solution and resulted in low corrosion resistance of the samples. Introducing Ag into Al_0.5CoCrFeNiCu_0.25 HEA led to the precipitation of a copper-silver eutectic structure, in which the copper regions were selectively dissolved in the sulfuric acid solution. Al_0.5CoCrFeNiCu_0.25 exhibited the best corrosion resistance with the corrosion current density of I_corr = 3.52 ± 0.02 μA/cm², significantly superior to that of the Al_0.5CoCrFeNi sample without copper and silver (I_corr = 6.05 ± 0.05 μA/cm²). Finally, the results indicated that suppressing elemental segregation by annealing or tailoring chemical composition is essential to improve the corrosion resistance of Al_0.5CoCrFeNiCu_xAg_y HEAs.

Al0.25CoCrFeNiV High Entropy Alloy Coating Deposited by Laser Cladding on Stainless Steel

This paper studies the microstructure, composition and properties of a Al_0.25CoCrFeNiV high entropy alloy coating (HEAC) deposited by laser cladding on austenitic-grade stainless steel. Laser cladding was carried out in an argon atmosphere on a FL-Clad-R-4 laser metal deposition complex with the following parameters: the laser power was 1400 W, the spot diameter was 3 mm, the track displacement was 1.2 mm, and the scanning speed was set to 10 mm/s. A change in the microstructure of the coating after laser cladding was revealed in comparison with as-cast high entropy alloy (HEA) Al_0.25CoCrFeNiV. A significant decrease was found in the size of vanadium precipitates, from 20-40 µm in the as-cast state to 1-3 µm after laser cladding. A change in microhardness over the thickness of the coating from 370 HV_0.3 at the outer surface to 270 HV_0.3 at the boundary with the substrate was established, which may be due to the diffusion of Fe from the stainless steel into the coating material during laser cladding. Despite these features, the resulting coating adheres tightly to the substrate, and has no cracks or other defects, which indicates the possibility of using laser cladding to create coatings from high entropy alloys.