What is Inconel, Incoloy and Monel Alloy

Inconel vs Incoloy vs Monel

What is Inconel Alloy: Nickel-Chromium-Iron, Heat and Corrosion Resistant Alloy

Inconel is a trademark registered by a company named the International Nickel Co (belong to Vale).

Inconel is one of the austenitic stainless steels with high resistance to heat. And its main component is nickel. Due to its reinforcing effect from the solid solution of molybdenum and niobium in Nickel-chromium alloy, it still shows a strong resistance to fatigue even when the temperature lowers to 1093 Celsius Degree. Therefore, it is widely applied in aviation industry, and suitable for the manufacturing of low load anti-oxidation parts of the temperature under 1100 Celsius Degree.

When the temperature is at 700 Celsius Degree, Inconel can show high tensile strength, fatigue strength, creep strength and fracture strength. When the temperature reaches 1000 Celsius Degree, it is highly resistant to oxidation. And if it is under low temperature, it has stable chemical properties, good welding performance and is easy to process.

Though this alloy is designed for high temperature environment, high content of chromium and molybdenum has made this alloy be applied in many corrosive media. From high oxidation environment to general corrosion one, it shows excellent corrosion resistance towards spots and fission. Besides, it also has superior corrosion resistance to chloride contaminated media such as seawater, geothermal water, neutral salt and brine.

Meanwhile, this alloy is highly formable and easier to be welded than many nickel-based alloys. When it is under welding, this alloy can still perform well in the resistance to intergranular corrosion. It has good tensile and fatigue properties when the temperature lowers to 980 Celsius Degree, and it is resistant to stress corrosion in salt spray atmosphere.

This alloy can be used as aircraft engine parts, jet aircraft engines, aerospace structural parts, and applied into chemical equipment, bellows compensator expansion joint, waste modern treatment equipment, occasions required with high mechanical stress and concerned with seawater, marine structures, salt water environment, etc.

Chemical Components of Inconel:

Inconel 625: Ni (62%) – Cr (23%) – Mo (9%)

Inconel718: Ni (55%) – Cr (21%) – Mo (2.8%

inconel 625 fittings

What is Incoloy: Nickel-Chromium-Iron Alloy

Incoloy is a trademark registered by a company named the International Nickel Co.

Incoloy belongs to nickel-chromium alloy, and it is an austenitic nickel-chromium-iron alloy of high strength solid solution. This alloy is designed to oxidation and carbonization when temperature rises. There are many types of Incoloy alloys, and the common ones include: Incoloy800, Incoloy800H, Incoloy800HT, Incoloy825, Incoloy840, Incoloy901, Incoloy925, Incoloy20, Incoloy330, Incoloy 25-6 Mo. Incoloy800 (800H and 800HT) are two most universal materials.

For Incoloy 800, 800H and 800HT, their chemical components are similar to each other, which makes all of them perform excellently in the resistance to reduction, oxidation and nitride, as well as shows high metallurgical stability in high temperature. However, due to different content of aluminum and titanium, these three alloys have different applications. For example, Incoloy 800 can be applied when the temperature is under -800 Celsius Degree, room temperature or the temperature over 600 Celsius Degree. As for Incoloy 800HT, because its content of aluminum and titanium does not exceed 0.7%, it shows good tensile strength when the temperature is over 600 Celsius Degree and still performs tough over 700 Celsius Degree. Incoloy 800H will be with excellent yield strength when the temperature goes over 700 Celsius Degree. And it is always applied in heat exchanger, bellow expansion joint compensator, electric heating tube, steel mill, heat treatment parts, acetic acid gypsum production and nuclear industry, etc. And it is supplied in forms of plate, strip, bar, pipe (welded pipe and seamless pipe), wire, forging, light rod, flange, and welding material.

Chemical Components:

Incoloy 825: 42Ni-30Fe-21.5Cr-3Mo-2.25Cu

What is Monel Alloy

Monel is a trademark registered by an American company named Special Metals.

Monel alloys have excellent physical properties of high strength, high corrosion resistance, and wear resistance. It has long service life in various acid and alkali medium, so that it is widely used in petrochemical industry, nuclear industry, national defense industry and other cutting-edge industries.

This alloy belongs to Ni-Cu corrosion resistant alloy, and it has two types:

Enhanced type for processing: Monel-400, 404, R405 and other brands;

Hardening type for precipitation: Monel K-500, 502 and other brands.

The most common ones are Monel-400 and K-500. Compared with Monel-400, K-500 has better mechanical properties, but performs poorer in the corrosion resistance. Monel-400 is the single-phase austenitic alloy with Ni-Cu solid solution, and its shows excellent corrosion resistance and strength under moderate temperature, especially in strong acid and alkali medium. Therefore, in recent years, the application of this alloy has been rising in petrochemical and nuclear industry in China.

Besides, Monel alloy has excellent corrosion resistance to reducing media, and can be stable in hydrofluoric acid, alkali, seawater, H2S, H2SO4, H3PO4, organic acid and many other corrosive media, especially in hydrofluoric acid and alkali solutions. This alloy is sensitive to SCC, and its working temperature is below 200 Celsius Degree.

 

In wide temperature ranges (up to 1000F), Monel-400 of copper-nickel alloy can have high strength. The spring made by Monel-400 can be applied in the corrosive environments with the temperature reaching 450F. And this alloy performs excellently in salt water of high concentrations. This alloy can be used as corrosion resistant components, elastic sensitive elements, and thermocouple protection tube which requires heat and corrosion resistance (Note: the operating temperature shall not exceed 500 Celsius Degree). And it is not recommended to be used in the oxidizing corrosive media.

Chemical Component of Monel 400:

Alloy

%

Ni

Cu

Fe

C

Mn

Si

S

Monel 400

Min.

63

28

 

 

 

 

 

Max.

 

34

2.5

0.3

2

0.5

0.024

 

Chemical Component of Monel K500:

Alloy

%

Ni

Cu

Al

Ti

Fe

Mn

S

C

Si

Monel K500

Min.

63

27

2.3

0.35

 

 

 

 

 

Max.

 

22

3.15

0.85

2.0

1.5

0.01

0.25

0.5

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