Inconel alloy, Inconel is a heat-resistant and corrosion-resistant nickel-chromium-iron alloy. Inconel is used for nickel, iron and cobalt-based alloys developed for applications that require excellent mechanical and chemical properties at high temperatures.
625 alloy steel is a solid-solution-strengthened nickel-based deformed high-temperature alloy with molybdenum and niobium as the main strengthening elements. It has excellent corrosion resistance and oxidation performance. It has good tensile properties and fatigue properties from low temperature to 980°C, and Resistant to stress corrosion in salt spray atmosphere. Nconel625 is an alloy grade with a density of 8.4 g/cm3 and a melting point of 1290-1350°C. It has excellent resistance to inorganic acid corrosion and has excellent corrosion resistance to various corrosive media in oxidation and reduction environments. Alloy 625 shows excellent corrosion resistance in many media. Excellent resistance to pitting, crevice corrosion, intergranular corrosion and erosion in chloride media
Inconel625 alloy is Inconel alloy, a low-carbon nickel-chromium-molybdenum-niobium alloy with excellent corrosion resistance to various corrosive media. Due to the low carbon content and the stabilization heat treatment, there will be no sensitization tendency even after being held at a high temperature of 650-900°C for 50 hours. The delivery state is a soft annealed state, and its application range includes wet corrosive environments, and it has obtained TÜV certification for pressure vessels with a temperature of -196 to 450°C. Another slightly adjusted performance is suitable for high temperature applications.
Chemical Composition of Inconel 625
The compositional range for Inconel 625 is provided in the table below.
| Element | Content |
| Ni | 58% min |
| Cr | 20 – 23% |
| Mo | 8 – 10% |
| Nb+Ta | 3.15 – 4.15% |
| Fe | 5% max |
 Typical Properties of Inconel 625
Typical properties of Inconel 625 are covered in the following table.
| Property | Metric | Imperial |
| Density | 8.44 g/cm3 | 0.305 lb/in3 |
| Melting point | 1350 °C | 2460 °F |
| Co-Efficient of Expansion | 12.8 μm/m.°C
(20-100°C) |
7.1×10-6 in/in.°F
(70-212°F) |
| Modulus of rigidity | 79 kN/mm2 | 11458 ksi |
| Modulus of elasticity | 205.8 kN/mm2 | 29849 ksi |
Properties of Supplied Materials and Heat Treated Materials
| Condition of Supply | Heat Treatment (After Forming) | |||
| Annealed/Spring Temper | Stress relieve at 260 – 370°C (500 – 700°F) for 30 – 60 minutes and air cool. | |||
| Condition | Approx Tensile Strength | Approx Service Temp. | ||
| Annealed | 800 – 1000 N/mm2 | 116 – 145 ksi | -200 to +340°C | -330 to +645°F |
| Spring Temper | 1300 – 1600 N/mm2 | 189 – 232 ksi | up to +200°C | up to +395°F |
Relevant Standards
Inconel 625Â is covered by the following standards:
- BS 3076 NA 21
- ASTM B446
- AMS 5666
This Inconel 625 has the following characteristics:
1. It has excellent corrosion resistance to various corrosive media in oxidation and reduction environments
2. Excellent resistance to pitting and crevice corrosion, and will not produce stress corrosion cracking caused by chloride
3. Excellent resistance to inorganic acid corrosion, such as nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid, and mixed acids of sulfuric acid and hydrochloric acid, etc.
4. Excellent resistance to corrosion of various inorganic acid mixed solutions
5. When the temperature reaches 40℃, it can show good corrosion resistance in various concentrations of hydrochloric acid solution
6. Good processability and weldability, no susceptibility to cracking after welding
7. The manufacturing certification of pressure vessels with wall temperature of -196~450℃
8. Certified by the American Society of Corrosion Engineers NACE Standard (MR-01-75) to meet the highest standard level VII for use in acid gas environments
Metallographic structure of Inconel 625
625 is a face-centered cubic lattice structure. When kept at about 650℃ for a long enough time, carbon particles and unstable quaternary phase will be precipitated and will be transformed into a stable Ni3(Nb,Ti) orthorhombic lattice phase. After solid solution strengthening, the molybdenum and niobium components in the nickel-chromium matrix will improve the mechanical properties of the material, but the plasticity will be reduced.
Corrosion resistance of Inconel 625
Alloy 625 shows excellent corrosion resistance in many media. It has excellent resistance to pitting, crevice corrosion, intergranular corrosion and erosion in chloride media. It has good resistance to inorganic acid corrosion, such as nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid, etc., and also has alkali and organic acid corrosion resistance in oxidation and reduction environments. Effective resistance to chloride ion reductive stress corrosion cracking. There is almost no corrosion in seawater and industrial gas environments, and it has high corrosion resistance to seawater and salt solutions, even at high temperatures. No sensitivity during welding. It is resistant to carbonization and oxidation in static or circulating environments, and is resistant to corrosion by chlorine-containing gases.
Application
Inconel 625 application range application areas are:
The softened and annealed low-carbon alloy 625 is widely used in the chemical process industry, and its good corrosion resistance and high strength enable it to be used as a thinner structural part. Alloy 625 can be used in situations where it is exposed to seawater and subjected to high mechanical stress. Typical application areas:
1. Components of organic chemical processes containing chlorides, especially where acid chloride catalysts are used
2. Used in the manufacture of digesters and bleaching tanks in the pulp and paper industry
3. Absorption tower, reheater, flue gas inlet baffle, fan (humidity), stirrer, baffle and flue in the flue gas desulfurization system
4. Used to manufacture equipment and components used in acid gas environments
5. Acetic acid and acetic anhydride reaction generator
6. Sulfuric acid condenser
Category
Deformation Inconel625
Deformed Inconel625 refers to a class of alloys that can be processed by hot and cold deformation, with a working temperature range of -253~1320℃, good mechanical properties, comprehensive strength and toughness indicators, and high oxidation and corrosion resistance. According to its heat treatment process, it can be divided into solid solution strengthening alloy and aging strengthening alloy.
1. Solid solution strengthened alloy
The operating temperature range is 900~1300℃, and the highest anti-oxidation temperature is 1320℃. For example, GH128 alloy has a room temperature tensile strength of 850MPa and a yield strength of 350MPa; a tensile strength of 140MPa at 1000°C and an elongation of 85%. The endurance life of the stress at 1000°C and 30MPa is 200 hours and the elongation rate is 40%. Solid solution alloys are generally used to make components such as combustion chambers and casings of aviation and aerospace engines.
2. Aging strengthened alloy
The operating temperature is -253~950℃, and it is generally used to make structural parts such as turbine discs and blades of aviation and aerospace engines. The working temperature of the alloy used to make the turbine disk is -253~700℃, which requires good high and low temperature strength and fatigue resistance. For example: GH4169 alloy, the highest yield strength at 650℃ is 1000MPa; the alloy temperature for making blades can reach 950℃, for example: GH220 alloy, the tensile strength of 950℃ is 490MPa, and the endurance life of 940℃, 200MPa is more than 40 hours.
Deformed Inconel625 mainly provides structural forgings, cakes, rings, bars, plates, pipes, strips and wires for aerospace, aviation, nuclear energy, petroleum and civil industries.
According to the service temperature of casting alloy, it can be divided into the following three categories:
The first category: Equiaxed crystal casting Inconel625 used at -253~650℃. This type of alloy has good comprehensive properties in a wide range of temperatures, especially at low temperatures that can maintain strength and plasticity without decreasing. For example, the K4169 alloy, which is used in aerospace and aerospace engines, has a tensile strength of 1000 MPa, a yield strength of 850 MPa, and a tensile plasticity of 15% at 650°C; its endurance life under stress of 650°C and 620 MPa is 200 hours. It has been used in the production of diffuser casings in aero engines and various complex structural parts for pumps in aero engines.
The second category: Equiaxed crystal casting Inconel625 used at 650~950℃. This type of alloy has higher mechanical properties and thermal corrosion resistance at high temperatures. For example, K419 alloy, at 950°C, the tensile strength is greater than 700MPa, and the tensile ductility is greater than 6%; at 950°C, the endurance strength limit for 200 hours is greater than 230MPa. This type of alloy is suitable for use as aero-engine turbine blades, guide vanes and cast turbines.
The third category: Directionally solidified columnar crystal and single crystal Inconel625 used at 950~1100℃. This kind of alloy has excellent comprehensive performance, oxidation resistance and thermal corrosion resistance in this temperature range. For example, DD402 single crystal alloy has a durability life of more than 100 hours under a stress of 1100°C and 130MPa. This is the highest temperature turbine blade material used in China, and it is suitable for making the first-stage turbine blades of new high-performance engines.
With the continuous improvement of precision casting technology, new special processes are also emerging. Fine-grain casting technology, directional solidification technology, CA technology of complex thin-walled structural parts, etc. have greatly improved the level of casting Inconel625, and the scope of application has been continuously improved.
Powder metallurgy Inconel625
Atomized Inconel625 powder, after hot isostatic pressing or hot isostatic pressing, and then forged into a production process to produce Inconel625 powder products. Using powder metallurgy technology, due to the fine powder particles and fast cooling rate, the composition is uniform, there is no macro segregation, and the crystal grains are fine, the hot working performance is good, the metal utilization rate is high, and the cost is low, especially the yield strength and fatigue performance of the alloy. Great improvement.
FGH95 powder metallurgy Inconel625 has a tensile strength of 1500MPa at 650℃; the endurance life is more than 50 hours under 1034MPa stress. It is currently a disc powder metallurgy Inconel625 with the highest level of strength under 650℃ working conditions. Powder metallurgy Inconel625 can meet the requirements of engines with higher stress levels. It is the material of choice for high-temperature components such as turbine discs, compressor discs and turbine baffles for engines with high thrust-to-weight ratio.
Oxide dispersion strengthening (ODS) alloy
It is a special Inconel625 formed by a unique mechanical alloying (MA) process, and ultra-fine (less than 50nm) ultra-stable oxide dispersion strengthening phase at high temperature is uniformly dispersed in the alloy matrix. The strength of the alloy can be maintained close to the melting point of the alloy itself, and it has excellent high temperature creep performance, superior high temperature oxidation resistance, carbon and sulfur corrosion resistance.
There are three main ODS alloys that have been commercially produced:
MA956 alloy can be used at a temperature of 1350℃ in an oxidizing atmosphere, ranking first among Inconel625 for its resistance to oxidation, carbon and sulfur corrosion. It can be used as a lining for aero engine combustion chambers.
The MA754 alloy can be used in an oxidizing atmosphere at a temperature of up to 1250°C and maintains a relatively high high temperature strength and resistance to alkali glass corrosion. It has been used to make aero-engine guide grate ring and guide vane.
MA6000 alloy has a tensile strength of 222MPa at 1100°C and a yield strength of 192MPa; at 1100°C, the 1000-hour endurance strength is 127MPa, ranking first among Inconel625 and can be used for aero engine blades.
ntermetallic high temperature material
Intermetallic high-temperature materials are a kind of high-temperature materials with important application prospects and light specific gravity that have been researched and developed recently. For more than ten years, basic research on intermetallic compounds, alloy design, process development and application research have been mature, especially in the preparation and processing technology, toughening and strengthening of Ti-Al, Ni-Al and Fe-Al materials , Mechanical properties and application research have made remarkable achievements.
Ti3Al-based alloys (TAC-1), TiAl-based alloys (TAC-2) and Ti2AlNb-based alloys have low density (3.8~5.8g/cm3), high temperature, high strength, high stiffness, excellent oxidation resistance, creep resistance, etc. Advantages, it can reduce the weight of structural parts by 35-50%. Ni3Al-based alloy, MX-246 has good corrosion resistance, wear resistance and cavitation resistance, showing an excellent application prospect. Fe3Al-based alloy has good oxidation resistance and corrosion resistance, high strength at medium temperature (less than 600°C), and low cost. It is a new material that can partially replace stainless steel.
Environment Inconel625
In many areas of the civil industry, the component materials in service are in a high-temperature corrosive environment. In order to meet the needs of the market, the Inconel625 series is classified according to the use environment of the material.
1. Inconel625 master alloy series
2. Anti-corrosion Inconel625 plates, rods, wires, belts, tubes and forgings
3. High-strength, corrosion-resistant Inconel625 bars, spring wires, welding wires, plates, strips, and forgings
4. Glass corrosion resistant series products
5. Environmental corrosion resistance, hard surface wear resistance Inconel625 series
6. Special precision casting parts (blades, turbocharged turbines, turbine rotors, guides, instrument joints)
7. Centrifuge, high temperature shaft and accessories for glass wool production 8. Cobalt-based alloy heat-resistant pad and slide rail for billet heating furnace
9. Valve seat ring
10. Casting “U”-shaped resistance band
11. Centrifugal cast pipe series
12. Nano material series products
13. Light specific gravity high temperature structural materials
14. Functional materials (expandable alloy, high temperature and high elastic alloy, constant elastic alloy series)
15. Biomedical materials series products
16. Target products for electronic engineering
17. Power plant nozzle series products
18. Stellite alloy wear-resistant sheet
19. Ultra-high temperature anti-oxidation corrosion furnace roller and radiant tube.
Application
Inconel 625 application range application areas are:
The softened and annealed low-carbon alloy 625 is widely used in the chemical process industry, and its good corrosion resistance and high strength enable it to be used as a thinner structural part. Alloy 625 can be used in situations where it is exposed to seawater and subjected to high mechanical stress. Typical application areas:
1. Components of organic chemical processes containing chlorides, especially where acid chloride catalysts are used
2. Used in the manufacture of digesters and bleaching tanks in the pulp and paper industry
3. Absorption tower, reheater, flue gas inlet baffle, fan (humidity), stirrer, baffle and flue in the flue gas desulfurization system
4. Used to manufacture equipment and components used in acid gas environments
5. Acetic acid and acetic anhydride reaction generator
6. Sulfuric acid condensation