What Is The Difference Between Inconel 625 And 825？

Basic Information

Inconel 625 alloy is based on nickel, with 21-23% chromium, 8-10% molybdenum and 3.15-4.15% niobium added. It is a typical solid solution strengthened alloy with excellent mechanical properties, corrosion resistance and welding performance, and its operating temperature range is from low temperature to 982°C. Inconel 625 contains a high amount of nickel than other grades of Inconel, and it is nickel-based superalloy. At higher temperature it has high strength and great resistivity. Against corrosion and oxidation it shows great protection. In nuclear and marine applications these specific advantages make it very useful.

Inconel 625 alloy service temperature ranges from cryogenic to 982°C. The alloy high strength is due to the stiffening effect of niobium and molybdenum, which locates in the nickel-chromium matrix. Therefore Inconel alloy does not need precipitation hardening treatments. Inconel 625 is an excellent choice for seawater applications due to high tensile strength, high corrosion-fatigue strength and resistance to chloride-ion stress-corrosion cracking. Apart from this, it exhibits excellent toughness and ductility at low temperature.

INCOLOY alloy 825 (UNS N08825 / W.Nr. 2.4858) alloy is based on nickel, with 30-35% iron, 20-23% chromium, 2-3% molybdenum and 0.5-1.5% copper added. The alloy's chemical composition is designed to provide excellent corrosion resistance against many corrosive environments. When compared to other Inconel grades, Incoloy 825 contains a moderate amount of nickel and is a nickel based superalloy. It consist a higher melting point but has low yield strength and a low tensile strength. And it contains chromium and nickel along with titanium, molybdenum and copper. It specifically provides an exceptional corrosion resistance to aqueous corrosion. Beside this, it exhibits oxidizing resistance and reducing acids such as phosphoric and sulfuric acids.

Chemical composition analysis of Incoloy 825 and Inconel 625

The two alloys are quite different in terms of composition. Incoloy 825 is an austenitic nickel-iron-chromium alloy that contains small amounts of molybdenum, copper, and titanium. Inconel 625, on the other hand, is a nickel-chromium-molybdenum alloy that contains small amounts of iron, manganese, and silicon. Inconel 625 is a nickel-based superalloy containing a high amount of nickel than other grades of Inconel whereas Inconel 825 is a nickel-based superalloy containing a moderate amount of nickel when compared to other grades of Inconel. The major difference between Inconel 625 and 825 is the nickel content; Inconel 625 contains about 58% of nickel while Inconel 825 contains about 36-48% of nickel. Moreover, they have different melting points as well. The melting point of Inconel 625 is 1350◦C, but it is 1400◦C for Inconel 825.

Apart from that, another important difference between Inconel 625 and 825 is their strength; Inconel 625 has a very high tensile strength and a yield strength when compared to Inconel 825. Inconel 625 alloy is more stringent in controlling impurity elements, such as lower sulfur and manganese contents, which makes Inconel 625 alloy have better instant performance and durability. The 825 alloy contains higher iron, which reduces the cost of the alloy and also reduces the corrosion resistance. Alloy 625 has a high nickel content and a higher molybdenum content giving it a better foundation to resist corrosion.

Chemical contents of Incoloy 825 and Inconel 625

Physical properties of Incoloy 825 and Inconel 625

In terms of mechanical properties, Inconel 625 alloy adds niobium and tantalum. The solid solution strengthening effect of these two elements is stronger than other elements, giving Inconel 625 alloy higher mechanical strength. At the same time, Inconel 625 alloy contains higher molybdenum and also has better strengthening effect. The table below compares the mechanical properties of the two alloy materials. Incoloy 825 strip provides enhanced resistance to corrosion from organic acids like formic acid or acetic acid, as well as environments containing chlorides such as seawater or brackish water.

Conversely, Inconel 625 strip demonstrates heightened corrosion resistance against reducing acids like sulfuric or phosphoric acid, along with environments abundant in chlorides or halides. One of the most important properties of any material is its tensile strength, i.e. the ability of a material to resist being stretched by a force. Inconel 625 alloy has a tensile strength of 125 ksi (862 MPa), while Inconel 825 alloy has a tensile strength of 100 ksi (690 MPa).

Differences in application

In terms of applications, the two alloys have some similarities, but also some significant differences. The different properties of the two alloys make them suitable for different applications. Both alloys are used in chemical processing equipment such as heat exchangers, pumps and valves; they are also used in petroleum refining equipment and other industrial components exposed to high temperatures and corrosive environments. However, because of its higher melting point and superior stress-break strength at elevated temperatures, alloy Inconel 625 is typically used in more demanding applications such as gas turbines and nuclear reactors, while alloy Inconel 825 is often used in less demanding applications such as exhaust manifolds and chemical processing equipment.

It can be seen that the application range of alloy 825 and alloy 625 are almost the same. This is because alloy 825 was designed as a cheaper alternative to alloy 625.

In conclusion, while both Inconel 625 vs Incoloy 825 are highly regarded materials in their respective fields, they differ significantly in composition, properties, and applications. Inconel 625 is primarily used in high-temperature applications where strength and oxidation resistance are paramount, while Incoloy 825 shines in chloride-rich environments due to its superior corrosion resistance. Thank you for reading our article and we hope it can help you to have a better understanding of the differences between Inconel 625 vs Incoloy 825. If you are looking for Inconel 625 & Incoloy 825 suppliers online now, we would advise you to contact JN Alloy.