Introduction

Inconel alloys are nickel-chromium alloys. They are famous for high strength, corrosion resistance, and heat resistance. Two of the most popular chromium-nickel-iron alloys are 625 and 718. Both belong to high-performance nickel superalloys. They are increasingly used in metal 3D printing.​Their Ni-Cr-based composition gives them excellent corrosion resistance and high-temperature resistance. Their excellent mechanical, thermal, and corrosion properties make them widely used in aerospace, industrial manufacturing, and military equipment.​ Nickel-based superalloys are relatively difficult to machine. But 3D printing enables complex designs with minimal material usage. It helps produce near-net-shape lightweight components. This minimizes machining requirements. So Inconel alloy 625 and 718 have become one of the fastest-growing materials in additive manufacturing.​They share many similarities. But they also have key differences.  Let’s take a closer look at these two alloys. This helps you choose the better option for your project.​

Chemical Composition

  • The first major difference between Inconel alloy 625 and 718 is their chemical composition.Both are nickel alloys, but each contains different amounts of various chemicals—this is their difference.

    Inconel alloy 625 is mainly a nickel-based alloy, while Inconel alloy 718 is a nickel-cobalt (Ni+Co)-based alloy. The use of nickel-cobalt in Inconel alloy 718 means it has higher hardness and strength. On the other hand, Inconel alloy 625 has higher chromium and molybdenum contents, so it is more corrosion-resistant.

    See the full comparison of the chemical compositions of Inconel alloy 625 and 718 below.

inconel 625
718

Properties

  • Inconel Alloy 625 and 718 share many common properties. Like most nickel alloys, both have high strength, good weldability, and corrosion resistance.

    However, their different chemical compositions mean they show different performance levels. Both alloys resist high temperatures, but Inconel alloy 718 has a wider melting range—1321-1393°C. Similarly, both show good corrosion resistance, but the higher levels of chromium and molybdenum make Inconel 625 more corrosion-resistant.

Applications

  • With extremely high strength and corrosion resistance, the properties of Inconel 625 and 718 can easily surpass other materials like traditional steel.

    Inconel alloy 718 is used in the aerospace industry for its high strength and high-temperature resistance. It is a very common material in this field—currently, it accounts for half the weight of modern aircraft turbojet engines.

    On the other hand, Inconel alloy 625 is suitable for applications under corrosive conditions, such as the marine industry. Seawater environments are highly corrosive; materials must have extremely high corrosion resistance to withstand the impact of such corrosive environments.

Product Forms

Both Inconel 625 and 718 are easy to form and weld, so they are easily available in various product forms.

Inconel alloy 625

Pipeline

Coil

Welding wire

Thin plates and sheets

Circular bar chart

Pipe fittings

Inconel alloy 718

Circular bar chart

Thin plates and sheets

Welding wire