What is the difference between nickel alloy 625 and 718?
Alloy 625 and Alloy 718, often referred to as Inconel 625 and Inconel 718, are both nickel alloys, high temperature alloys, and both belong to the Inconel family of alloys. So, what is the difference between Inconel 625 and 718?
What is the difference between Inconel 625 and 718?
We will break down the differences between Inconel 625 and Inconel 718, from chemical composition to recommended uses. First, let's cover terminology.
Terminology
You may notice that we switch back and forth between Inconel 625 and Alloy 625 throughout this article. Rather than having you Google "Inconel 625 and Alloy 625" yourself, we want to explain what these names mean.
When we use the terms Inconel 625 and Alloy 625, we are referring to the same alloy. Inconel is a registered trademark of Specialty Metals Corporation. Therefore, for legal purposes, most alloy suppliers refer to it as Alloy 625 instead of Inconel 625.
Composition
The first major difference between Inconel 625 alloy and 718 alloy is their chemical composition. Both are nickel alloys, but each contains varying amounts of various chemicals that make them different.
Alloy 625 is primarily nickel-based, while Alloy 718 is primarily nickel + cobalt (Ni+Co). The use of Ni+Co in Alloy 718 means that it is harder and stronger. Alloy 625, on the other hand, has higher levels of chromium and molybdenum, which makes it more corrosion resistant. See below for a full comparison of the chemical compositions of Inconel 625 and 718.
Properties
Inconel 625 and Inconel 718 share many common properties. Like most nickel alloys, both alloys are high strength, easy to weld, and corrosion resistant.
However, due to the different chemical compositions of the two alloys, they differ greatly in these properties. While both alloys offer heat resistance, Alloy 718 has a higher melting point of 1321-1393°C. Likewise, while both alloys offer good corrosion resistance, Alloy 625 has higher levels of chromium and molybdenum, making it more corrosion resistant.
Applications
Inconel 625 and Inconel 718 are used in a variety of industries and applications. However, their individual compositions and properties make each alloy excel in certain areas.
Applications of Inconel 625
Inconel 625 is most commonly used in the oil and gas industry due to its excellent corrosion resistance. This makes it the alloy of choice for subsea equipment. It is also used in the aerospace industry in corrosive environments such as exhaust systems, furnaces, and engine thrust reversers.
Applications of Inconel 718
Inconel 718 is a mainstay material in the aerospace industry. Its superior heat resistance makes it ideal for applications in high temperature environments, including engine components. It is also used in high-performance automotive engines in the motorsports industry.
Product Forms
Both Inconel 625 and 718 are easy to form and weld, so they are available in a variety of product forms.
Inconel 625 Product Forms
Pipes
Coil
Wire
Sheets
Round Bars
Fittings
Flanges
Inconel 718 Product Forms
Round Bars
Sheets
Wire
