Effects of laser remelting speeds on microstructure, immersion corrosion, and electrochemical corrosion of arc-sprayed amorphous Al-Ti-Ni coatings

An arc-sprayed amorphous Al-Ti-Ni coating on S355 structural steel was processed using a laser remelting (LR). The surface and cross-section morphologies, chemical compositions, phases and residual stresses of obtained Al-Ti-Ni coatings at the LR speeds of 5, 10, and 15 mm/s were analyzed using a field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), and X-ray diffraction stress tester, respectively, and the effects of LR speeds on their immersion corrosion and potentiodynamic polarization curves of Al-Ti-Ni coatings in 3.5% NaCl solution were also investigated to analyze the mechanism of corrosion resistance. The results show that the metallurgical bonding is formed at the Al-Ti-Ni coating interface due to the interdiffusions and recombinations of Al, Ti, Ni, Fe, Cr and Mn. The Al-Ti-Ni coatings at the different LR speeds obtain a certain amount of amorphous phases, which are detected as AlFe, AlFe3, AlCrFe2, Ni2MnAl, and AlNi phases. The residual stresses of as-obtained Al-Ti-Ni coatings at the LR speeds of 5, 10, and 15 mm/s are −12 ± 8, 43.9 ± 3, and −34.4 ± 8 MPa, respectively, of which the tensile residual stress exacerbates the immersion corrosion and the compressive stress restrains the crack expansion. The corrosion potentials of Al-Ti-Ni coatings at the LR speeds of 5, 10, and 15 mm/s are −1.046, −1.106, and −0.986 V, respectively, which shift positively than S355 steel and effectively increase the corrosion resistance of substrate, the electrochemical corrosion resistance of Al-Ti-Ni coating at the LR speed of 15 mm/s is the best among the three kinds of coating.