Corrosion Resistance of Niobium and Vanadium Carbide Layers Produced by Thermoreactive Diffusion Treatments on Spheroidal Cast Iron

Sample composition was 0.03C-0.22Si-17.86Cr-3.91Ni-2.14Mo-1.96Nb (in wt%). Samples of those materials were treated in salt bath (a composite of sodium borate, aluminum, iron-niobium or iron-vanadium or iron-chromium) at 1000 °C for 2 hours after a powder carburizing treatment at 1000 °C for 2 hours, used to increase the surface carbon content and enable such treatment. The objective of this study was to evaluate the possibility of using TRD process in stainless steel to improve its tribological characteristics through the production of carbide layers. Characterization of this layers was obtained by SEM, EDX, XRD, hardness Vickers tests, micro-abrasive wear tests (fixed ball) and corrosion tests by potentiodynamic polarization in aqueous solutions of NaCl (3.5 % by weight). The efficiency of the layered surface in increasing wear and corrosion resistance was demonstrated by submitting it to micro-abrasive wear tests and potentiodynamic polarization corrosion tests.