Effects of chromium addition on microstructure and properties of TiC–VC reinforced Fe-based laser cladding coatings

• In situ TiC–VC reinforced Fe-based coatings with different Cr addition were obtained.
• Some long strip Cr3C2 synthesized while the Cr addition was 12.0% or more.
• A moderate amount of Cr improved hardness and corrosion resistance significantly.
• The cladding layer microhardness could reach as high as 1090HV0.2 with 3.0% Cr.
• The corrosion resistance could improve 4.5 times with 12.0% Cr.

Effects of different addition of Cr on microstructure and properties (especially the corrosion resistance) of cladding layers were investigated by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), potentio-dynamic polarization and electrochemical impedance spectroscopy (EIS). Results showed that Fe–Ti–V–C alloy powders with different addition of Cr formed good cladding layers without defects such as cracking and porosity. Phases of the cladding layers were α-Fe, γ-Fe, TiC, VC and TiVC2. A certain amount of long strip Cr3C2 synthesized while the addition of Cr was 12.0% or more. Microhardness and corrosion resistance of cladding layer both improved greatly with a moderate amount of Cr. The cladding layer with 3.0% Cr showed a highest microhardness 1090HV0.2, and the variation tendency of the hardness is not a linearly relationship with increasing the chromium addition. The cladding layer with 12.0% Cr addition showed the best corrosion resistance, which was about 4.5 times than that of the cladding layer without Cr. EIS spectrum of the cladding layer without Cr was composed of an inductive arc at low frequency and a capacitive arc at high frequency. However, the inductive arc at low frequency transformed into a capacitive arc gradually with the addition of Cr increasing.