Microstructure evolution and corrosion behavior of Fe-Al-based intermetallic aluminide coatings under acidic condition
(1. College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China;
2. School of Materials Science and Engineering, North University of China, Taiyuan 030051, China;
3. College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 211800, China;
4. School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China)
2. School of Materials Science and Engineering, North University of China, Taiyuan 030051, China;
3. College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 211800, China;
4. School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China)
Abstract: Two Fe-Al-based intermetallic aluminide coatings were fabricated on 430-SS (Fe-Cr) and 304-SS (Fe-Cr-Ni) substrates by pressure-assisted solid diffusion bonding with coating on pure Fe as control. The microstructure and intermetallic phases of the coatings were characterized by SEM, EDS and EBSD. A network of Cr2Al13 with matrix of Fe4Al13 was formed by inter-diffusing of Al with the substrates. The corrosion behavior of intermetallic coatings was investigated in 0.5 mol/L HCl solution by mass-loss, OCP, Tafel plot and EIS. It was found that corrosion resistance was greatly enhanced by dozens of times after the addition of Cr and Ni compared with that on pure Fe. The presence of cracks in the coating on 430-SS provided a pathway for corrosion media to penetrate to the substrate and accelerated the corrosion rate. Moreover, the corrosion product was analyzed by XRD, demonstrating that the addition of Cr and Ni facilitated the formation of more corrosion resistant phases, and therefore improved corrosion resistance.
Key words: intermetallic; iron aluminide; stainless steel; hydrogen chloride; corrosion