Inconel 625 (UNS N06625)
Inconel 625 is a nickel-based wrought superalloy with molybdenum and niobium as primary strengthening components. It is made up of nickel, chromium, molybdenum, and niobium, as well as traces of iron, carbon, and other elements. Inconel 625 has excellent corrosion and pitting resistance, and it will not create stress corrosion cracking due to chlorides. It also has strong corrosion resistance to various corrosive media in oxidizing and reducing environments. It also exhibits similar corrosion resistance in extremely corrosive conditions such as seawater, acid, and alkali; when temperatures approach 40 °C, it can exhibit good corrosion resistance in varied concentrations of hydrochloric acid solutions.
Inconel 625 has outstanding high-temperature strength, capable of strong mechanical strength and hardness at low temperatures of around 982°C (1800°F). The structure of alloy 625 is a face-centered cubic lattice. Carbon particles and an unstable quaternary phase will precipitate and change into a stable Ni3(Nb, Ti) orthorhombic lattice phase if held at 650 °C for a long enough time. The addition of molybdenum and niobium to the nickel-chromium matrix following solid solution strengthening improves mechanical characteristics while decreasing plasticity. Inconel 625 has good tensile and fatigue qualities from room temperature to 980 °C and can be utilized to make aero-engine parts, aerospace structural parts, and chemical equipment.
Chemical Composition (%) of Inconel 625 (UNS N06625)
| CHEMICAL COMPOSITION (%) | ||||||||||||
| C, max | Mn, max | P, max | S, max | Si, max | Cr | Ni | Mo | Fe, max | Al, max | Ti, max | Nb | Co, max |
| 0.10 | 0.50 | 0.015 | 0.015 | 0.50 | 20.00-23.00 | Rest | 8.00-10.00 | 5.00 | 0.40 | 0.40 | 3.15-4.15 | 1.00 |
Mechanical Properties of Inconel 625 (UNS N06625)
| MECHANICAL PROPERTIES | ||||
| Tensile Strength, MPa, min | Yield Strength, MPa, min | Elongation (%), min | Hardness, max | |
| 760 | 345 | 30 | 220 HB | 287 HRC |
Physical Properties of Inconel 625 (UNS N06625)
| PHYSICAL PROPERTIES | ||||||
| Density | Melting Point | Modulus of Elasticity | Poisson's Ratio | Coefficient of Thermal Expansion | Thermal Conductivity | Electrical Conductivity |
| 8.4 g/cm³ | 1290-1350 ℃ | 200 GPa | 0.29 | 13 µm/m·K | 11 W/m·K | 1.3% IACS |
Features of Inconel 625 (UNS N06625)
- High strength
- Excellent resistance to pitting and crevice corrosion
- Excellent resistance to chloride stress corrosion cracking
- Excellent resistance to general and localized corrosion
- Excellent oxidation resistance and high-temperature resistance
- Good processability and weldability
- Good ductility and toughness
Applications of Inconel 625 (UNS N06625)
Inconel 625 is widely used in aerospace, chemical industry, marine, and other industries.
- Engine case
- Fuel manifold
- Flue gas desulfurization system
- Sulfuric acid condenser
- Acetic acid and acetic anhydride reaction generator
- pressure vessel
- Pulp and paper equipment
Equivalent Grades of Inconel 625 (UNS N06625)
| Grade | UNS | WERKSTOFF NR. | GB | BS | JIS | AFNOR |
| Inconel 625 | N06625 | 2.4856 | GH3625 | NA21 | NCF625 | NC22DNb |
Hot Forming of Inconel 625 (UNS N06625)
Inconel 625 should be hot-processed at temperatures ranging from 1150 °C to 900 °C, with water quenching or other rapid cooling methods used for cooling. When heated, the material can be directly sent into a furnace that has been heated to the highest working temperature, and after a sufficient time of heat preservation (60 minutes of heat preservation time is required for each 100mm thickness), it is quickly released from the furnace and thermal processing is carried out in the specified temperature range's high-temperature section. Reheating is required when the material's temperature falls below the thermal processing temperature. Hot working is followed by annealing for optimum performance and corrosion resistance.
Cold Forming of Inconel 625 (UNS N06625)
During cold working, Inconel 625 requires interim annealing. It should harden at a faster pace than austenitic chromium-nickel stainless steel.
Weldability of Inconel 625 (UNS N06625)
Inconel 625's outstanding welding capabilities allow it to combine with other metal components of varying compositions; hence, Inconel 625 filler metal can be utilized to weld other materials. Alloy 625 can be welded manually or automatically using techniques such as GTAW (gas tungsten arc welding), gas metal arc welding, resistance welding, and so on.
Corrosion Resistance of Inconel 625 (UNS N06625)
In various mediums, Inconel 625 offers good corrosion resistance. It resists pitting corrosion, crevice corrosion, intergranular corrosion, and chloride medium corrosion extremely well. It is resistant to inorganic acids such as nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid, and others, as well as alkali and organic acids in oxidizing and reducing conditions. Resists chloride ions effectively and prevents stress corrosion cracking. In seawater and industrial gas settings, there is essentially no corrosion, and it has great corrosion resistance to seawater and saline solutions even at high temperatures. There is no sensation during welding. In static or cyclic conditions, it is resistant to carbonation and oxidation, and it is resistant to corrosion by chlorine-containing gases.
