High Temperature Chloride Corrosion Behavior of 904L:AlFeNiMoNb High-Entropy Alloy

In order to obtain high cost-effective coating materials working in chlorine-containing environment at high temperature, a 904L super austenitic alloy modified by an AlFeNiMoNb alloy (904L:AlFeNiMoNb) was obtained by vacuum arc melting process. The 904L:AlFeNiMoNb high-entropy alloy has a similar phase component with the AlFeNiMoNb alloy, but a more homogenous microstructure than that of the AlFeNiMoNb alloy. High-temperature chloride corrosion tests for 904L, AlFeNiMoNb, and 904L:AlFeNiMoNb high-entropy alloy were carried out under N-2-2.6 vol.% CO2-1.3 vol.% O-2-2,700 vppm HCl gaseous environment at 700 degrees C and 800 degrees C for 55 h, respectively. Due to the volatilization of FeCl2, weight change curves of the 904L alloy at 700 degrees C and 800 degrees C showed obvious weight loss. Especially at 800 degrees C, the weight loss of the corroded 904L sample was 10 times that of the corroded sample at 700 degrees C. Different from the weight loss situation of the 904L sample, both AlFeNiMoNb and 904L:AlFeNiMoNb high-entropy alloy showed small weight gains under the corrosion temperature of 700 degrees C, while the latter gained half as much weight as the former. When the corrosion temperature was raised to 800 degrees C, the AlFeNiMoNb and 904L:AlFeNiMoNb high-entropy alloy showed flat weight change curves with little weight loss. Weight loss for the AlFeNiMoNb and 904L:AlFeNiMoNb high-entropy alloy were 1.35138 and 0.0118 mg/cm(2), respectively. The high temperature chloride corrosion resistance of 904L:AlFeNiMoNb high-entropy alloy is higher than that of 904L and AlFeNiMoNb at both 700 degrees C and 800 degrees C. Meanwhile, on the basis of the morphology and composition results of the corroded samples, combined with thermodynamic calculation, the high-temperature chloride corrosion mechanics of the tested alloys were discussed.