Abstract:ABSTRACT The effect of V on hot corrosion behavior of cast Ni-base superalloy K417G exposed to 75%Na2SO4+25%NaCl at 900℃ for 100h has been investigated by means of thermogravimetry(TG) and scanning electron microscopy equipped with energy dispersive X-ray spectrum(EDS), corrosion resistance obtained by measuring the polarization curve at 900℃.the results showed that The hot corrosion rate of the alloy with 0.016 v content is almost unchanged, the hot corrosion rate of alloy increased with the increase of V content. but the hot corrosion rate of alloy with 1.19 V content is more 100 times than the low V alloy. The corrosion product on the surface of K417G alloys is found to be composed of oxide and sulfides is still made up of three layer, that is the external oxide layer consists of Al、Cr、Ti and Ni, sulfides formed in different layer of NiS、MoS and NiCrS. With the content of V content, S element diffusion toward to interlayer, and the layer of Al2o3 and Cr2o3 become thinner, hence the inner sulfides layer formed in the alloy with 1.19 V which can decreased the corrosion resistance. Com pared with the alloy with 1.19 V, the results of the polarization curve showed that the corrosion potential shift 0.4V toward positive direction, the corrosion resistance of the alloy with 0.016 V is better than that alloy with high V content.