Discover What Inconel 625 used for?
One of Gnee Steel's most popular products, Inconel 625 alloy has a long history and a wide range of uses. In this article from Langley Alloys, we will review the history of Inconel 625 alloy and its applications in a variety of industrial fields. Read on to learn more about this fascinating and extremely useful alloy.
The Origins of Inconel 625
Inconel 625 (UNS06625, 2.4856, BS3076 NA21) was originally developed in the 1960s and has been used for more than 50 years in a variety of demanding applications requiring high strength, high toughness, ease of fabrication, corrosion resistance and a wide operating temperature range.
Early applications tended to be those requiring higher operating temperatures, such as aerospace, jet engines and gas turbines. Its mechanical properties remain stable over a wide temperature range; it can be used stably up to 650 degrees Celsius with little loss of mechanical properties, and it retains most of its strength even at temperatures up to 800 degrees Celsius and even cryogenically. Nickel-based alloys have low expansion at elevated temperatures, some creep resistance under high stress conditions, and are corrosion resistant.
Modern Applications of Inconel 625
Today, many of these applications require the supply of 625 alloy to AMS 5666. AMS is an aerospace material specification, and 5666 covers the supply of bars, rings, forgings, and certain tube sizes. While the composition and mechanical properties of 625 alloy vary slightly compared to other common specifications, testing and certification are different.
625 alloy is currently widely used in the oil and gas industry. It has excellent corrosion resistance, with a pitting resistance equivalent value (PREN) greater than 45, which is much higher than 718 alloy and super duplex stainless steel. It is recognized as suitable for sour services (containing H2S) according to NACE MR1075 / ISO 15156-3 and API 6A for "Wellhead and Christmas Tree Equipment".
Properties of Inconel 625
In addition to its excellent corrosion resistance, Inconel 625 is non-magnetic and spark resistant. These physical properties are very useful in applications such as downhole equipment and tools for oil and gas exploration. Risers, pipe hangers, and high-strength fasteners all take advantage of the properties of 625 alloy. Gas processing equipment such as fluid separation units will also use 625 alloy due to its oxidation resistance and good thermal fatigue strength. Since its microstructure is essentially austenitic, its manufacturing and processing process is fairly simple as long as the appropriate tools and configurations are used.
Applications of Inconel 625
Inconel 625 has been widely used in marine applications such as propellers, drive shafts, and thrusters due to its excellent resistance to seawater corrosion. However, due to its relatively high cost, it is often replaced by super duplex stainless steel or duplex stainless steel in these applications. These grades have corrosion resistance and service life beyond acceptable levels and are higher in strength.
Incoloy 625 has a wide range of potential applications in the chemical processing industry due to its good resistance to oxidizing and reducing acids, excellent toughness and ease of machining. As a result, it is used in valve trims for more demanding end-use applications in this market segment. Sensors and thermowells take advantage of the high impact toughness and extremely wide operating temperature range of Incoloy 625, as well as its easy machining properties.
Pollution control, gas scrubbers and waste treatment facility construction will use 625 alloy to protect against corrosive, hot exhaust gases that may contain halides. The exhaust systems of high-performance sports cars also use the alloy, but are limited to Formula 1 and other levels of racing due to cost. More niche applications include nuclear power components, such as control rods.
Perhaps the biggest challenge in using 625 alloy is its relative cost compared to other grades. Excellent corrosion resistance and ease of fabrication make it the material of choice for less corrosion-resistant cladding. A thin layer of 625 alloy is usually applied by weld deposition and then machined to achieve a consistent surface finish. Automation of the process helps keep it cost competitive.
