Nickel Chrome Molybdenum Seawater Corrosion Resistant Materials Research

Two new fabrication route and its process parameters about the seawater corrosion resistant Ni-Cr-Mo alloy had been investigated by means of optical microscopy Scanning electron microscopy(SEM), X-ray diffraction(XRD), mechanical test and corrosive test.Ni-Cr-Mo alloy prepared by the route of common mold -vacuum-sintering, the result showed that when sintering temperature not higher than 1330℃ , relative density , line shrinkage rate, tensile strengths, hardness and corrosion-resistance of alloy increased slowly with the ascension of sintering temperature; when sintered at 1360℃, these properties increase quickly; when sintered at 1390℃, the shape of samples were distorted. So in the route of common mold and vacuum-sintering, properties of alloy sintered in vacuum at 1360℃ /2h were best, its ob was 504MPa, was 8.8 % corrosion rate was 0.123mm/a.Ni-Cr-Mo alloy prepared by the route of hot-pressing -solid-solution treatment, the result showed that the properties of alloy after solid-solution treatment were better than before solid-solution treatment; ductility, strength and corrosion-resistance of alloy increased with the ascension of solid-solution temperature; when solid-solution temperature at 1300℃, synthetic properties of alloy was best excellent; increasing sequentially solid-solution temperature, these properties descended, alloy properties increased after solid-solution treatment mainly because solid-solution degree of Cr and Mo in Ni were strengthened, and some intermetallic compounds which were not benefit to property were eliminated.Compared with the route of common mold -vacuum-sintering(1360℃ /2h), the route of hot-pressing(1225℃/40min) -solid-solution treatment(1300℃/4h)could obtain Ni -Cr-Mo alloy with better mechanical and corrosion resistant properties, its ob was 715MPa, was 17.2% corrosion rate was 0.051 mm/a . So the best route was hot-pressing(1225℃/40min) -solid-solution treatment(1300℃/4h).The effect of W and Cu on the mechanical and corrosion resistant properties of Ni-Cr-Mo alloy had also been investigated in this dissertation. The study showed that Synthetic properties of alloy adding both W and Cu were best excellent, its ob was 694MPa, was 15.8%, corrosion rate was 0.002mm/a. Because the alloy element W have strong function of solid-solution and made Nickel-base alloy having good blindside and point corrosion resistance in Cl-. Cu is a kind of alloy element having pluser electric potential, so in the process of corrosion, it can be accumulated in large quantity on alloy surface, and can make further corrosion resistance increasing.