Alloy 625 (Inconel) is a nickel-chromium-molybdenum alloy with a small niobium and tantalum addition. It is an excellent general purpose material for elevated temperature use in high strength, oxidation problem areas and finds particular application in the aerospace and offshore oil & gas industries. Alloy 625 shows excellent resistance to a variety of corrosive media.
Alloy 625 demonstrates excellent resistance to pitting, crevice corrosion, stress corrosion, corrosion fatigue and erosion corrosion whilst maintaining its mechanical properties up to about 450 ºC. It is highly resistant to a wide range of organic and mineral acids combined with good corrosion resistance to high temperature sulphides and chlorides. The niobium and tantalum within the matrix act in conjunction with the molybdenum to provide a high strength alloy without the need for additional heat treatment.
Related Specifications of Alloy 625 (Inconel)
- NACE MR 0175
- ISO 15156-3
- AMS 5666
- ASTM B446
- NiCr22Mo9Nb (EU)
Nominal Composition of Alloy 625 (Inconel)
Ni 58.0%min, Cr 20%~23%, Mo 8.0%~10%, Nb & Ta 3.15%~4.15%
Mechanical Properties of Alloy 625 (Inconel)
|Ultimate Tensile Strength (N/mm²)
||Proof Stress (N/mm²)
Due to its low carton content and stabilizing heat treatment, Inconel 625 show little tendency to sensitization even after 50 hour at temperatures in the range 650°C
The alloy is supplied in the soft-annealed condition for applications involving wet corrosion (Alloy 625, grade 1), and is approved by TUV for pressure vessels in the temperature range -196 to 450C.For high-temperature applications, above appro 600 C, where high strength and resistance to creep and rupture are required, a solution-annealed version(Alloy 625, grade 2)with a higher carbon content is normally employed and available on request in some products forms.
Outstanding resistance to pitting, crevice corrosion, and inter granular attack Almost complete freedom from chloride-induced stress-corrosion cracking;
Good resistance to mineral acids, such as nitric, phosphoric, sulphuric and hydrochloric acids; Good resistance to alkalis and organic acids
Good mechanical properties
The high alloy content of alloy 625 enable it to withstand a wide variety of severe corrosion environment. In mild environments such as the atmosphere, fresh and sea water, neutral salts, and alkaline media there is almost no attack In more severe corrosion environment the combination of nickel and chromium provides resistance to oxidizing chemical, whereas the high nickel and molybdenum contents supply resistance to non oxidizing against sensitization during welding, thereby preventing subsequent inter granular cracking. Also, the high nickel content provides from chloride ion-stress-corrosion cracking
The soft-annealed version of Alloy 625(grade 1) is preferred for applications in the chemical process industrv. in
marine engineering and in pollution control equipment for environment protection. Typical applications are:
1.Superphosphoric acid production equipment
2.Nuclear wastes reprocessing equipment:
3.Sour gas production tubes:
4.Piping systems and sheathing of risers in oil exploration
5.Offshore industry and marine equipment;
6.Flue gas scrubber and damper components:
For high-temperature application, up to approximately 1000C, the solution-annealed version of Alloy 525 (grade 2) can be used in accordance to the ASME code for pressure vessels. Typical application are
- Components in waste gas system and waste gas cleaning plants exposed to higher temperatures
- Flare stacks in refineries and offshore platform:
- Recuperator and compensators
- Submarine diesel engine exhaust systems:
- Superheater tubes in wastes incineration plants.