Abstract
For this study, aimed at proposing a potential direction to prevent sulfuric acid dew point corrosion, a Ni–Cr–Mo alloy Hastelloy C22 coating was fabricated by coaxial laser cladding technology. The phase composition, microstructure, and corrosion behavior in a simulated sulfuric acid dew point corrosion environment were investigated and compared with a Hastelloy C22 alloy, a titanium alloy TC4, and 09CrCuSb steel (ND). The results showed that the phase composition of the C22 coating is essentially similar to that of the C22 alloy, consisting of a γ-Ni solid solution and Ni6Mo6C1.06. The finer microstructure of the C22 coating mainly contains eutectic and dentrite, presenting a typical solidification feature of laser cladding. The corrosion resistance of the C22 coating is very close to that of the C22 alloy, and outclasses that of TC4 and ND. The corrosion behavior of the C22 coating is intergranular corrosion resulting from the segregation of molybdenum, chromium containing corrosion products, and smaller anode micro-batteries.
Highlights
Sulfuric acid dew point corrosion caused by low-temperature flue gas exists extensively in the backend of coal-fired boilers and gives rise to the severe failure of components [1,2,3,4,5,6]
Serious corrosion caused by concentrated sulfuric acid in low temperature (
There is a difference in the phase content between C22 bulk and the C22 coating according to the diffraction peak intensity of the two specimens
Summary
Sulfuric acid dew point corrosion caused by low-temperature flue gas exists extensively in the backend of coal-fired boilers and gives rise to the severe failure of components [1,2,3,4,5,6]. After contacting with the low-temperature surfaces of devices, the sulfuric acid vapor in the flue gas condenses into sulfuric acid droplets because of the temperature’s sharp decrease [7,8,9,10]. China [16,17,18,19], the flue gas is sharply cooled down to only 50 ◦ C or lower and mixed with a larger amount of water vapor and droplets in the WFGD system. Employing anti-corrosion materials and surface treatment technology is considered as an effective solution from the standpoint of economic efficiency and complete reliability of the facilities [24,25,26,27]
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