What are the differences in chemical composition between Monel, Inconel, Incoloy and Hastelloy grades?
What are the differences in chemical composition between Monel, Inconel, Incoloy and Hastelloy grades?
Overview
Monel 400, Monel K-500, Inconel 600, Inconel 625, Inconel 718, Inconel X-750, Incoloy 800, Incoloy 800H, Incoloy 825, Incoloy A-286 and Hastelloy C-276 are the most common nickel alloy grades. The chemical composition is as follows:
In this article, we will explore together the role and impact of different chemical elements in these grades.
The role of different elements in nickel alloys
Nickel alloys are the most widely used and strongest high-temperature alloys. Nickel in nickel alloy is an austenite stabilizing element, which enables the nickel alloy to maintain the FCC structure, thereby dissolving more other alloying elements while maintaining good structural stability and material plasticity.
Cr, Mo, and Al play an antioxidant and anti-corrosion role, and have a certain reinforcing effect. The modes of action of nickel alloy strengthening elements can be divided into the following three types:
Ⅰ. Solid solution strengthening elements
Due to the different atomic radii of basic atoms, solid solution strengthening elements (such as W, Mo, Co, Cr, V, etc.) can form local lattice strains in the Ni-Fe structure to achieve the effect of strengthening the material.
Ⅱ. Precipitation enhancing elements
Precipitation strengthening elements such as Al, Ti, Nb, Ta, etc. can form overall orderly A3B-type intermetallic compounds, such as Ni3 (Al, Ti) and other strengthening phases (γ'), so that the alloy can be effectively strengthened and obtain better results than iron. Higher high temperature strength of base alloys and cobalt based alloys.
3. Grain boundary strengthening elements
Grain boundary strengthening elements, such as B, Zr, Mg, rare earth elements, etc., can improve the high temperature performance of the alloy.
Differences Between Monel, Inconel, Incoloy and Hastelloy Grades
Typically, grades of nickel alloys are named by the manufacturers who developed them. For example:
Ni-Cu alloy is also called Monel alloy, such as Monel 400 and Monel K-500.
Ni-Cr alloys are generally called Inconel alloys, such as Inconel 600 and Inconel 625, which are common heat-resistant nickel alloys. They are mainly used under oxidizing media conditions.
If more iron is added to Inconel alloy instead of nickel, it will become Incoloy alloy, such as Incoloy 800, Incoloy 825, etc. They are not as resistant to high temperatures as precipitation hardened nickel alloys, but they are cheaper. They can be used in cryogenic components of jet engines and reactors in petrochemical plants.
If precipitation strengthening elements (Ti, Al, Nb, etc.) are added to Inconel and Incoloy, it will become precipitation hardening nickel alloys such as Inconel 718 and Incoloy A-286, which can still maintain good mechanical strength and corrosion resistance at high temperatures. They are mainly used in jet engine components.
Ni-Cr-Mo(-W)(-Cu) alloy is called Hastelloy, in which Ni-Cr-Mo is mainly used to reduce media corrosion. Representative grades of Hastelloy include Hastelloy C-276, C-2000, etc.
