Microstructure and corrosion properties of plasma-sprayed NiCr-Cr3C2 coatings comparison with different post treatment

The effects of laser and plasma arc remelting on the microstructure and properties of plasma-sprayed NiCr-Cr3C2 coatings on steel substrates have been investigated. The microstructure of the coatings has been analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM), It is found that the Cr3C2, delta-(CrNi), Cr7C3 and Cr23C6 phases were obtained for both coatings, before and after remelting treatment. The laser remelting was operated in a continuous way with 800 W power in different scan speed, while the plasma arc remelting was operated with plasma cladding machine under different scan currents. However, the denser microstructure of both remelted coatings can be obtained, especially for the plasma arc remelted coating. The Vickers microhardness measurement showed certain enhancement values for both remelted coatings. The corrosion behavior was evaluated through salt spray corrosion (SSC) method. Energy-dispersive spectroscopy (EDS) showed that the chloride was produced during SSC process. The higher corrosion resistance for plasma arc remelted coating may be due to the more compact microstructure, less porosity rate and tensile residual stress. Compared with laser remelting method, plasma arc remelting is a cheap, convenient and effective remelting method. (C) 2007 Elsevier B.V. All rights reserved.