Effect of molybdenum, iron and chromium on the properties of Ni-Mo alloy

a: Effect of molybdenum on nickel properties
The effect of molybdenum on the electrochemical behavior of nickel in acidic media such as sulfuric acid and hydrochloric acid is extremely important. Adding molybdenum to nickel makes the electrochemical behavior of the alloy change the corrosion resistance of the alloy in hydrochloric acid and sulfuric acid. The actual corrosion test results confirmed that the corrosion resistance increased as the molybdenum content increased.
It can be seen from the corrosion experiment results that in the hydrochloric acid medium, when the Mo content (mass fraction) in the alloy exceeds 15%, the corrosion resistance of the alloy is significantly improved. When the Mo content reaches 30%, the corrosion resistance is at The best condition, filled with air, accelerates the corrosion of the alloy.

b: Effect of iron and chromium on properties of Ni-Mo alloy
In order to reduce the cost of Ni-Mo alloy and improve the plastic toughness of Ni-Mo alloy, the role of iron and chromium in Ni-Mo alloy was studied in depth. The influence of iron on the corrosion potential of Ni-Mo alloy with different molybdenum content in hydrochloric acid, the potential changes to the negative direction with the increase of iron content, and the alloy with w=(mo)=30% is particularly remarkable.
The effect of iron on the corrosion resistance of solid solution Ni-Mo alloy in hydrochloric acid is also important. In hydrochloric acid, for a Ni-Mo alloy with a Mo content of w = (mo) = 30%, iron having a mass fraction of less than 10% has no effect on the corrosion resistance of the solid solution alloy. In the aging state, iron inhibits the formation of phase B and reduces the hardening effect of the alloy. However, the excessively high iron content is favorable for the formation of the Y phase rich in Mo to produce a lean Mo region, which is detrimental to the corrosion resistance of the alloy.
The results show that for the conventional 0Mo28Ni65Fe5 (Hastelloy B) alloy, Fe with a mass fraction of 4% can inhibit the precipitation of the hard and brittle Ni4Mo phase, which is beneficial to improve the plastic toughness and corrosion resistance of the alloy. For low-carbon, low-silicon and Hastelloy B-2 alloys with a mass fraction of less than 2% Fe, proper control of iron content and chromium content can improve the plastic toughness and corrosion resistance of the alloy. The effect of Fe + Cr on the aging performance of Hastelloy B-2 alloy is shown in Figure 7-14. The precipitation of phase B is suppressed with the increase of iron content, thereby improving the toughness of the alloy. In the solid solution state, the impact absorption energy of the alloy is more than 200J, and the impact performance of the alloy is obviously reduced after aging. As the iron content increases, the curve shifts to the right, and the iron content w=(Fe) is 5.86% Ni-Mo alloy. Even at 650 degrees, 700 degrees, 750 degrees, 800 degrees and 8 hours aging, the impact absorption work is still above 140J, and the proper amount of iron has a significant effect in suppressing the precipitation of phase B.

c: The effect of Fe + Ci content on the corrosion resistance of Ni-Mo alloy is obvious. The results of these tests show that sufficient Fe + Cr content is very effective for improving the plasticity of the aged state of Ni-Mo alloy and improving the corrosion resistance of the alloy, thereby reducing or inhibiting cracks during equipment manufacturing and generating SCC during use. The danger.