Surface and cross-section characteristics and immersion corrosion behavior of laser thermal sprayed amorphous AlNiCoCrY2O3 coatings

Amorphous AlNiCoCrY2O3 coatings were fabricated on S355 structural steel using a laser thermal spraying (LTS) at the laser powers of 1100, 1300 and 1500 W. The surface and cross-section morphologies, distributions of chemical elements, phases and residual stresses of as-obtained AlNiCoCrY2O3 coatings were analyzed using a scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), and X-ray stress tester, and X-ray photoelectron spectroscopy (XPS), respectively. The immersion corrosion behaviors of AlNiCoCrY2O3 coatings in 3.5% NaCl solution for 720 h and electrochemical corrosions were investigated to analyze their corrosion resistance. The results show that the laser thermal sprayed AlNiCoCrY2O3 coatings are composed of crystal NiCrCoMo and AlNi phases, accompanied with the amorphous NiCrFe and AlFeNi, the Al exists in the binding state of Al3Ni, Al2O3 and AlNi. The residual stress of AlNiCoCrY2O3 coatings fabricated at the laser powers of 1100, 1300 and 1500 W induced by LTS is 0 ± 0, −123.1 ± 62, 0 ± 0 MPa, respectively, of which compressive stress comes from elastic anisotropy. After the immersing corrosion test, the Cl− is attached on the atoms-zones of NiCrFe and NiCrCoMo, and easily forms the corrosion products of Al2O3 film on the atoms-zones of AlNi and AlFeNi, which prevent the Cl− from entering into the substrate. The corrosion speed of AlNiCoCrY2O3 coating fabricated at the laser power of 1100 W is 0.0045 mm/a, which is lower than those fabricated at the laser powers of 1300 and 1500 W, effectively improving its electrochemical corrosion resistance.