What are the structural characteristics of Monel 400 alloy?
Monel 400 alloy is called ni68cu28fe alloy in China. The chemical composition of the alloy is mainly composed of 30% Cu and 65% Ni with a small amount of Fe (1% ~ 2%). The microstructure is typical single phase austenite. Since nickel and copper can be mutually soluble in any proportion, there is no intermetallic phase precipitation.

What about the corrosion resistance of Monel 400 alloy steel?

As we have said before, nickel copper alloy is more resistant to corrosion in reducing medium than pure nickel, and more resistant to corrosion in oxidizing medium than pure copper. Since Monel 400 alloy has a single phase austenite structure, there is no corrosion caused by galvanic reaction between different phases in the alloy.

Monel 400 alloy has very high corrosion resistance in the atmosphere and belongs to the extremely corrosion resistant alloy.

In water corrosion, Monel 400 alloy not only has excellent corrosion resistance, but also has little pitting corrosion and stress corrosion. In natural water and distilled water, the corrosion rate of the alloy is generally less than 0.025 mm / A, including many harsh conditions such as different temperature, different flow rate and air filling. The corrosion of ni688cu28fe alloy will be aggravated in acidic pulp water containing oxidizing salts, but it is still one of the corrosion resistant materials. Monel 400 alloy has excellent corrosion resistance in natural and artificial seawater. In seawater, an important use of Monel 400 is to manufacture and purchase structural components for seawater corrosion protection in splash zone of the platform. In still sea water, pitting corrosion of the alloy steel is easy to occur, but the pitting propagation is slow.

The oxidation resistance of Monel 400 alloy is lower than that of pure nickel at high temperature and in air and oxygen. The outer layer of the oxide film on the alloy surface contains CuO and Cu Ψ o, while the inner layer is rich in nickel, which is basically pure nickel oxide. The maximum temperature of Monel 400 alloy working continuously in air is generally considered to be about 600 ℃. In high temperature steam, the service temperature of Monel 400 alloy should be ≤ 485 ℃ no matter it is dry or wet steam. The erosion resistance of the alloy is also very good in high velocity steam.