Overview of inconel 625

Inconel625 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 excellent corrosion resistance to various corrosive and reducing environments.

Alloy 625 exhibits excellent corrosion resistance in many media. Excellent resistance to pitting, crevice corrosion, intergranular corrosion and erosion in chloride media.

Inconel 625 similar grades:

The chemical composition of Inconel 625:

The minimum mechanical properties of Inconel 625 alloy at room temperature:

Characteristics of inconel 625 alloy:

1. Excellent corrosion resistance to various corrosive media in oxidizing and reducing environments;

2. Excellent resistance to pitting corrosion and crevice corrosion, and no stress corrosion cracking due to chloride;

3. Excellent resistance to inorganic acid corrosion, such as nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid, and mixed acid of sulfuric acid and hydrochloric acid;

4. Excellent resistance to corrosion of various inorganic acid mixed solutions;

5. When the temperature reaches 40 °C, it can show good corrosion resistance in various concentrations of hydrochloric acid solution;

6. Good processability and weldability, no post-weld cracking sensitivity;

7. Manufacturing certification of pressure vessels with wall temperatures between -196 and 450 °C;

8. Certified by the American Society of Corrosion Engineers NACE Standard (MR-01-75) to the highest standard grade VII for use in acid gas environments.

Metallographic structure of Inconel 625

625 is a face-centered cubic lattice structure. When held at about 650 ° C for a sufficient period of time, carbon particles and an unstable quaternary phase will precipitate and will be converted to a stable Ni 3 (Nb, Ti) orthorhombic lattice phase. The molybdenum and niobium components in the nickel-chromium matrix after solid solution strengthening will improve the mechanical properties of the material, but the plasticity will be reduced.

Corrosion resistance of Inconel 625

Alloy 625 exhibits excellent corrosion resistance in many media. 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 the oxidation and reduction environment. Effective against chloride ion reductive stress corrosion cracking. It hardly corrodes in seawater and industrial gas environments, and has high corrosion resistance to seawater and salt solutions, as well as at high temperatures. No sensitivity during welding. It is resistant to carbonization and oxidation in static or cyclic environments and is resistant to chlorine-containing gases.

Classification of Inconel 625

Deformation Inconel625

Deformed Inconel 625 is a kind of alloy which can be processed by hot and cold deformation and has an operating temperature range of -253 to 1320 °C. It has good mechanical properties and comprehensive strength and toughness indexes and has high anti-oxidation and corrosion resistance. According to the heat treatment process, it can be divided into a solid solution strengthening alloy and an age strengthening alloy.

1. Solid solution strengthened alloy

The operating temperature range is 900-1300 ° C, and the highest antioxidant temperature is 1320 ° C. For example, GH128 alloy has a tensile strength of 850 MPa at room temperature and a yield strength of 350 MPa; a tensile strength of 140 MPa at 1000 ° C, an elongation of 85%, a permanent life of 1000 ° C, 30 MPa stress of 200 hours, and an elongation of 40%. Solid solution alloys are generally used to make components such as aerospace and aerospace engine combustion chambers and casings.

2, aging strengthening alloy

The operating temperature is -253 to 950 °C, which is generally used to fabricate structural parts such as turbine disks and blades for aerospace and aerospace engines. The working temperature of the alloy for making the turbine disk is -253 to 700 ° C, and it is required to have good high and low temperature strength and fatigue resistance. For example: GH4169 alloy, the highest yield strength at 650 ° C up to 1000 MPa; the alloy temperature of the blade can reach 950 ° C, for example: GH220 alloy, 950 ° C tensile strength is 490 MPa, 940 ° C, 200 MPa longevity of more than 40 hours.

Inconel 625 mainly provides structural forgings, cakes, rings, bars, plates, tubes, strips and wires for the aerospace, aerospace, nuclear and petroleum industries.

Casting Inconel625

Cast Inconel 625 is a type of Inconel 625 that can or can only be molded by casting. Its main features are:

1. Having a wider composition range Since the deformation processing performance can be avoided, the design of the alloy can be focused on optimizing its performance. For the nickel-based Inconel 625, the γ' content can be adjusted to 60% or higher by adjusting the composition, so that the alloy can maintain excellent performance at a temperature of up to 85% of the melting point of the alloy.

2. Has a wider application field Due to the special advantages of the casting method, Inconel 625 castings with arbitrarily shaped structures or shapes can be designed and manufactured according to the needs of the parts.

According to the use temperature of the cast alloy, it can be divided into the following three categories:

The first type: Isopel 625, which is used at -253 to 650 °C, has a good overall performance over a wide range of temperatures, especially at low temperatures. For example, the K4169 alloy with a large amount on the aerospace and aerospace engines has a tensile strength of 1500 °C of 1000 MPa, a yield strength of 850 MPa, and a tensile ductility of 15%. The 650 ° C, 620 MPa stress has a long life of 200 hours. It has been used to make diffuser casings in aerospace engines and complex structural components for various pumps in aerospace engines.

The second category: Isconel625, an equiaxed crystal casting used at 650-950 °C, has high mechanical properties and resistance to hot corrosion at high temperatures. For example, K419 alloy, tensile strength greater than 700 MPa, tensile plasticity greater than 6% at 950 ° C; 950 ° C, 200 hours of permanent strength limit greater than 230 MPa. These alloys are suitable for use as aero-engine turbine blades, guide vanes and cast-in turbines.

The third category: directional solidification columnar crystals used at 950 to 1100 ° C and single crystal Inconel 625 alloys have excellent overall properties and resistance to oxidation and hot corrosion in this temperature range. For example, the DD402 single crystal alloy has a long-lasting life of more than 100 hours under a stress of 1100 ° C and 130 MPa. This is the most used turbine blade material in the country and is suitable for the production of first-class turbine blades for 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, and CA technology of complex thin-walled structural parts have greatly improved the level of cast Inconel 625 and the application range has been continuously improved.

Powder Metallurgy Inconel625

Inconel 625 powder is manufactured by atomizing Inconel 625 powder, hot isostatic pressing or hot isostatic pressing and then forging production. Powder metallurgy process, due to the fine powder particles, fast cooling, uniform composition, no macrosegregation, fine grain, good thermal processing performance, high metal utilization rate, low cost, especially the yield strength and fatigue properties of the alloy. A big increase.

FGH95 powder metallurgy Inconel625, 650 ° C tensile strength 1500MPa; 1034MPa stress under the long-lasting life of more than 50 hours, is currently the highest strength level of 650 ° C working conditions of a disk powder metallurgy Inconel625. Powder metallurgy Inconel625 meets the requirements of engines with higher stress levels and is the material of choice for high temperature components such as engine turbine discs, compressor discs and turbine baffles.

Oxide dispersion strengthened (ODS) alloy

It is a special mechanical alloying (MA) process, which is formed by ultra-fine (less than 50nm) ultra-stable oxide dispersion strengthening phase uniformly dispersed in the alloy matrix at high temperature to form a special Inconel625. The alloy strength can be maintained close to the melting point of the alloy itself, and has excellent high temperature creep properties, superior high temperature oxidation resistance, and resistance to carbon and sulfur corrosion.

There are three main types of ODS alloys that have been commercialized:

MA956 alloy can reach the temperature of 1350 °C under oxidizing atmosphere, which is the first place in Inconel625 for oxidation, carbon and sulfur corrosion resistance. Can be used in aviation engine combustion chamber lining.

MA754 alloy can be used in an oxidizing atmosphere at temperatures up to 1250 ° C and maintains a relatively high temperature strength and resistance to alkali glass corrosion. It has been used to make aero-engine guide ring and guide vanes.

MA6000 alloy has a tensile strength of 222 MPa at 1100 ° C and a yield strength of 192 MPa. At 1100 ° C, the 1000-hour permanent strength is 127 MPa, ranking first in Inconel 625 and can be used in aero-engine blades.

Intermetallic compound high temperature material

High-temperature materials for intermetallic compounds are a kind of light-weight high-temperature materials with important application prospects recently developed. For more than a decade, basic research on metal compounds, alloy design, process development and application research have matured, especially in the preparation, processing and toughening of Ti-Al, Ni-Al and Fe-Al materials. , remarkable achievements in mechanical properties and applied research.

Ti3Al based alloy (TAC-1), TiAl based alloy (TAC-2) and Ti2AlNb based alloy have low density (3.8 ~ 5.8g / cm3), high temperature and high strength, high steel and excellent oxidation resistance, creep resistance, etc. The advantage is that the structural member can be reduced by 35 to 50%. Ni3Al based alloy, MX-246 has excellent corrosion resistance, wear resistance and cavitation resistance, showing excellent application prospects. Fe3Al-based alloy has good anti-oxidation and anti-corrosion properties. It has 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 series Inconel625 is classified according to the environment in which the materials are used.

1, Inconel625 mother alloy series

2, corrosion-resistant Inconel625 plates, rods, wires, belts, tubes and forgings

3, high strength, corrosion resistant Inconel625 bar, spring wire, welding wire, plate, strip, forgings

4, glass corrosion resistant products

5, environmental corrosion resistance, hard surface wear-resistant Inconel625 series

6, special precision casting parts (blade, turbo turbine, turbine rotor, guide, instrument connector)

7. Centrifuge for glass wool production, high temperature shaft and auxiliary parts 8, cobalt-based alloy heat-resistant blocks and slide rails for billet heating furnace

9, valve seat

10, casting "U" shaped resistance tape

11, centrifugal casting tube series

12, nano material series products

13, light specific gravity high temperature structural materials

14. Functional materials (expanded alloy, high temperature and high elasticity alloy, constant elastic alloy series)

15. Biomedical materials series

16. Target series products for electronic engineering

17, power device nozzle series products

18, Stellite alloy wear-resistant sheet

19. Ultra-high temperature anti-oxidation corrosion furnace roller and radiant tube.

Inconel625 way to increase strength

Solid solution strengthening

Adding elements different in the size of the base metal atom (chromium, tungsten, molybdenum, etc.) causes distortion of the matrix metal lattice, adding elements that reduce the stacking fault energy of the alloy matrix (such as cobalt) and adding can slow down the diffusion rate of the matrix elements. Elements (tungsten, molybdenum, etc.) to strengthen the matrix.

Precipitation strengthening

By aging treatment, the second phase (γ', γ", carbide, etc.) is precipitated from the supersaturated solid solution to strengthen the alloy. The γ' phase is the same as the matrix, and is a face-centered cubic structure, and the lattice constant is similar to the matrix. And coherent with the crystal, so the γ phase can be uniformly precipitated in the form of fine particles in the matrix, hindering the dislocation motion, and producing significant strengthening effect. The γ' phase is an A3B type intermetallic compound, A represents nickel, cobalt, and B represents Aluminum, titanium, niobium, tantalum, vanadium, tungsten, and chromium, molybdenum, iron can be either A or B. The typical γ' phase in Ni-based alloys is Ni3 (Al, Ti). The strengthening effect of γ' phase It can be enhanced by:

1 increase the number of γ' phases;

2 to make the γ' phase and the matrix have a suitable degree of mismatch to obtain the strengthening effect of coherent distortion;

3 adding yttrium, lanthanum and other elements to increase the anti-phase boundary energy of the γ' phase to improve its ability to resist dislocation cutting;

4 Adding elements such as cobalt, tungsten, molybdenum and the like to increase the strength of the γ' phase. The γ" phase is a body-centered tetragonal structure, and its composition is Ni3Nb. Because of the large mismatch between the γ" phase and the matrix, a large degree of coherent distortion can be caused, and the alloy obtains a high yield strength. However, when it exceeds 700 ° C, the strengthening effect is significantly reduced. Cobalt-based Inconel 625 is generally free of gamma phase and is reinforced with carbide.

Grain boundary strengthening

At high temperatures, the grain boundary of the alloy is a weak link, and the addition of trace amounts of boron, zirconium and rare earth elements improves the grain boundary strength. This is because rare earth elements can purify grain boundaries, boron and zirconium atoms can fill grain boundary vacancies, reduce the grain boundary diffusion rate during creep, inhibit the aggregation of grain boundary carbides and promote the spheroidization of grain boundary second phase. In addition, the addition of an appropriate amount of niobium to the cast alloy can also improve the strength and ductility of the grain boundaries. It is also possible to form a chain-shaped carbide at the grain boundary by heat treatment or to cause a curved grain boundary to improve plasticity and strength.

Oxide dispersion strengthening

By the powder metallurgy method, a fine oxide which remains stable at a high temperature is added to the alloy in a dispersed state, thereby obtaining a remarkable strengthening effect. The oxides usually added are ThO2, Y2O3 and the like. These oxides strengthen the alloy by obstructing dislocation motion and stabilizing the dislocation substructure.

Inconel625 manufacturing process

Inconel 625 with or without aluminum and titanium is generally smelted in an electric arc furnace or a non-vacuum induction furnace. Inconel 625 with high aluminum and titanium is not easily controlled when it is smelted in the atmosphere, and gas and inclusions are more intensive, so vacuum smelting should be used. In order to further reduce the content of inclusions, improve the distribution of inclusions and the crystal structure of the ingot, a double process combining smelting and secondary remelting may be employed. The main means of smelting are electric arc furnace, vacuum induction furnace and non-vacuum induction furnace; the main means of remelting are vacuum self-consumption furnace and electroslag furnace.

Solid solution strengthened alloys and alloy ingots containing aluminum and titanium (the total amount of aluminum and titanium are less than about 4.5%) may be forged blanks; alloys containing aluminum and titanium are generally extruded or rolled. Then hot rolled into a material, some products need to be further cold rolled or cold drawn. Larger diameter alloy ingots or cakes are forged with a hydraulic press or a fast forging hydraulic press.

Alloys with a high degree of alloying and non-deformation are currently widely used for precision casting, such as casting turbine blades and guide vanes. In order to reduce or eliminate grain boundaries perpendicular to the stress axis in the cast alloy and to reduce or eliminate looseness, a directional crystallization process has been developed in recent years. This process is to grow crystal grains in a crystal direction during solidification of the alloy to obtain parallel columnar crystals without lateral grain boundaries. The primary process condition for achieving directional crystallization is to establish and maintain a sufficiently large axial temperature gradient and good axial heat dissipation conditions between the liquidus and the solidus. In addition, in order to eliminate all grain boundaries, it is also necessary to study the manufacturing process of single crystal blades.

Powder metallurgy process, mainly used to produce precipitation-enhanced and oxide dispersion-strengthened Inconel625. This process allows plasticity and even superplasticity to be obtained for cast Inconel 625, which is generally indeformable.

The overall performance of Inconel 625 is closely related to the microstructure of the alloy, which is controlled by metal heat treatment. Inconel 625 is generally heat treated. Precipitation-strengthened alloys are usually solution treated and aged. The solid solution strengthened alloy is only subjected to solution treatment. Some alloys undergo one or two intermediate treatments before aging. The solution treatment is firstly to dissolve the second phase into the alloy matrix so that the strengthening phase such as γ, carbide (cobalt-based alloy) is uniformly precipitated during the aging treatment, and secondly, in order to obtain a suitable grain size to ensure high temperature creep. And lasting performance.

The solution treatment temperature is generally from 1040 to 1220 °C. Currently widely used alloys are treated with intermediate treatment at 1050 to 1100 °C before aging treatment. The main effect of the intermediate treatment is to precipitate carbides and γ films at the grain boundaries to improve the grain boundary state. At the same time, some alloys also precipitate some γ phases with larger particles and form a reasonable match with the fine γ phases precipitated during aging treatment. The purpose of the aging treatment is to uniformly precipitate the γ phase or the carbide (cobalt-based alloy) to increase the high temperature strength, and the aging treatment temperature is generally 700 to 1000 ° C.

Inconel625 trends

The development trend of Inconel625 is to further improve the working temperature of the alloy and improve the ability to withstand various loads at medium or high temperatures, extending the life of the alloy. In the case of turbine blade materials, single crystal blades will enter the practical stage, and the overall performance of the oriented crystal blades will be improved.

In addition, it is possible to use a chilled alloy powder to produce a multi-layer diffusion-connected hollow blade to accommodate the need to increase the temperature of the gas. In the case of the guide vane and the combustion chamber material, it is possible to use an oxide dispersion-strengthened alloy to greatly increase the use temperature. In order to improve the corrosion resistance and corrosion resistance, the protective coating materials and processes of the alloy will also be further developed.

Inconel625 Technology Development

Microstructure and properties of high gradient directional solidification eutectic Inconel625

K4169Inconel625 Structure Refinement and Performance Optimization Study

Dissolution and transformation of Ni_5Zr in cast nickel-based Inconel625

Effect of orientation process and niobium content on a nickel-based Inconel625

The role of Mg in Inconel625 GH220

Second phase study of GH2027 iron-based Inconel625

Exploratory Study on Adding Carbonized Matter Points to Ni_3Al Based Inconel625

Precipitation of MC and M_3B_2 phase in a Ni-Cr-CoInconel625

High temperature low cycle fatigue behavior of nickel-based Inconel625 GH4145/SQ

Research on Transformation of Deformed Inconel625 in Forming Quality Control

Microstructure and properties of high gradient directional solidification eutectic Inconel625

K4169Inconel625 Structure Refinement and Performance Optimization Study

Dissolution and transformation of Ni_5Zr in cast nickel-based Inconel625

Effect of orientation process and niobium content on a nickel-based Inconel625

The role of Mg in Inconel625 GH220

Microstructure and phase analysis of FGH95 powder Inconel625 stress aging

Study on Microstructure and γ' Phase Precipitation Kinetics of Rene'88DT Powder Inconel625

Study on Crack Initiation and Expansion Behavior of Inclusions in Nickel-Based Powder Inconel625

Micromechanical Behavior of Inclusions in Nickel-Based Powder Inconel625

Research and development of powder Inconel625

Inconel 625 substance application:

Inconel625 is a kind of metal material which can work for a long time under the action of high temperature and certain stress above 600 °C based on iron, nickel and cobalt. It has high temperature strength, good oxidation resistance and corrosion resistance. Comprehensive performance such as fatigue performance and fracture toughness. Inconel 625 is a single austenitic structure with good structural stability and reliability at various temperatures. Based on the above performance characteristics, Inconel 625 has a high degree of alloying and is also called “superalloy”. It is widely used. An important material for aviation, aerospace, petroleum, chemical, and shipbuilding. Inconel 625 is divided into iron, nickel, cobalt and other Inconel 625 according to the matrix element. Iron-based Inconel 625 can only be used at temperatures up to 750-780 ° C. For heat-resistant parts used at higher temperatures, nickel-based and refractory metal-based alloys are used. The nickel-based Inconel 625 is particularly important in the entire Inconel 625 field and is used extensively to manufacture aerospace jet engines and the hottest end parts of various industrial gas turbines. If the 150MPA-100H permanent strength is the standard, the current maximum temperature that the nickel alloy can withstand is >1100 °C, while the nickel alloy is about 950 °C, and the iron-based alloy is <850 °C, that is, the nickel-based alloy is correspondingly 150 °C higher. Up to about 250 °C. Therefore, nickel alloy is called the heart of the engine. At present, on advanced engines, nickel alloys account for half of the total weight, not only turbine blades and combustion chambers, but also the use of nickel alloys in turbine blades and even later stages of compressor blades. Compared with ferroalloys, nickel alloys have the advantages of high operating temperature, stable structure, less harmful phase and high resistance to oxidation and corrosion. Compared to cobalt alloys, nickel alloys can work at higher temperatures and stresses, especially in moving blades.

The advantages of nickel alloys described above are related to some of their superior properties. Nickel is a face-centered cube, the structure is very stable, and no homogenous transformation occurs from room temperature to high temperature; this is important for the selection of matrix materials. It is well known that austenitic structures have a number of advantages over ferrite structures.

Nickel has high chemical stability, almost no oxidation occurs below 500 degrees, and is not affected by warm air, water and certain salt aqueous solutions at the school temperature. Nickel dissolves very slowly in sulfuric acid and hydrochloric acid, but dissolves quickly in nitric acid.

Nickel has a large alloying ability, and even adding more than ten kinds of alloying elements does not cause harmful phases, which provides a potential possibility for improving various properties of nickel.

Although the mechanical properties of pure nickel are not strong, the plasticity is excellent, especially the plasticity changes at low temperatures.

Inconel 625 application range and application areas:

The soft annealed low carbon alloy 625 is widely used in the chemical process industry, with good corrosion resistance and high strength enabling it to be a thin structural component. Alloy 625 can be used in applications where it is exposed to sea water and subjected to high mechanical stresses. Typical application areas:

1. Components of chloride-containing organic chemical process processes, especially where acid chloride catalysts are used

2. Distillers and bleachers for the pulp and paper industry

3. Absorption tower, reheater, flue gas inlet baffle, fan (wet), agitator, deflector and flue in flue gas desulfurization system

4. Equipment and components used in the manufacture of acid gas environments

5. Acetic acid and acetic anhydride reaction generator

6. Sulfuric acid condenser

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