Reviewing the history of corrosion resistant alloys, it is not difficult to conclude that the development of Ni-Fe-Cr-Mo alloys stems from the conclusions of two technical ideas. One is to replace some of the Ni and Mo in the alloy on the basis of the alloy, and to increase the Cr content of the alloy accordingly. The alloy formed not only maintains the oxidation resistance, reduction and corrosion properties of the oxidation-reduction medium of the alloy. , which reduces costs. The second is to alloy Ni-Fe-Cr-Mo alloy with Mo to improve the corrosion resistance of the Ni-Fe-Cr alloy and improve its pitting corrosion resistance and crevice corrosion resistance. Regardless of the technical idea developed by Ni-Fe-Cr-Mo alloy, the common feature is that the mass fraction is 18%~25%Cr, 5%~13%Mo. In order to obtain a stable austenite structure and good thermal stability of the structure, the nickel content is adjusted according to the chromium and molybdenum contents in the alloy. Since the composite effect of Mo and Cu is higher than that of pure Mo in improving corrosion resistance, the development and application of Ni-Fe-Cr-Mo alloy is far less than that of Ni-Fe-Cr-Mo-Cu alloy.
The results of a study on a boiling Niflex solution (1 mol/L HNO3-2 mol/L HF acid) dissolved in a Zr alloy and a stainless steel cladding and a boiling Sulfex solution (4-6 mol/L H2SO4) in a stainless steel cladding showed that for 45Ni-22Cr -Fe and 50Ni-25Cr-Fe alloys, only when the molybdenum content reaches 6%, the corrosion rate of such alloys is reduced to the lowest point, and then the increased molybdenum content has no significant effect on the corrosion resistance of the alloy. The effective data in the wet process phosphoric acid indicates that the molybdenum content of the alloy plays an important role in the corrosion resistance of the Ni-Fe-Cr alloy containing 30% to 40% Ni and 20% to 29% Cr. In order to provide suitable corrosion resistance, the molybdenum content in the alloy increases as the phosphoric acid concentration and the Cl- content increase. In 38% H3PO4, when the Cl – content is 3000 x 10~6, an alloy containing 8% Mo is required. When the Cl – content is 100 X 10~6, the mass fraction is 6% Mo. Alloy; in 28% H3PO4, an alloy with a mass fraction of 4% Mo is used when the Cl- content is 3000 x 10 -6, and an alloy with a mass fraction of 2% Mo is used when the Cl – content is 100 X 10 -6 To meet the requirements of use. In the oxidation-reduction composite medium containing p-etching and crevice corrosion containing CI-, Cu2+, Fe3+ and being acidic, Mo has a significant effect on the corrosion resistance of 43% Ni-20Cr-Fe alloy. Corrosion resistance The molybdenum content is increased and increased. When the molybdenum content Mo reaches 13.5%, the corrosion rate is zero. In the case of pitting, in this environment, the mass fraction of 12.5% Mo is a limit below which pitting is generated, above which no pitting occurs.
Typical materials for Ni-Fe-Cr-Mo iron-nickel based corrosion resistant alloys are: N06002, N06060, N08320, N08135
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Post time: Mar-13-2019