Evaluating the metallurgical and corrosion characteristics of HVOF-sprayed Ni and Ni-TiB2 coatings on duplex stainless steel

This study investigates the influence of nickel (Ni) and nickel-titanium diboride (Ni-TiB2) coatings on corrosion resistance properties. The coatings were applied to a duplex stainless steel (DSS) 2205 substrate via high velocity oxygen fuel (HVOF) spraying with ball milled Ni and Ni-TiB2 powder. The microstructure, phase distribution, and phase structure of the HVOF coatings were analysed using scanning electron microscopy (SEM), Electron Backscatter Diffraction (EBSD), and X-ray diffraction (XRD). The corrosion properties of the Ni and Ni-TiB2 composite coatings were systematically evaluated at both room and high temperature conditions, compared with those of uncoated DSS2205 substrates. The Ni-TiB2 coating demonstrated superior corrosion resistance, performing 6.5 times better than the Ni coating and 11.6 times better than untreated samples due to its protective passivation layer. In high-temperature corrosion tests, after 50 cycles, uncoated DSS2205 steel showed a mass change of 62.4 mg, whereas Ni coating reduced this to 43.4 mg, and Ni-TiB2 coating further reduced to 35.6 mg. The corrosion mechanisms at both room temperature and high temperatures were examined, revealing that the Ni-TiB2 composite coating demonstrated significantly superior corrosion resistance compared to the uncoated DSS2205 and Ni coated samples. The SEM morphological analysis supported this.