GH3625 (GH625) alloy is a solid solution strengthened nickel-based deformed superalloy with molybdenum and niobium as the main strengthening element. It has excellent corrosion resistance and oxidation resistance, and has good tensile properties and fatigue properties from low temperature to 980 degrees Celsius. And resistant to stress corrosion in salt spray atmosphere. Therefore, it can be widely used in the manufacture of aero-engine parts, aerospace structural parts and chemical equipment.
product description
1.1. Alloy characteristics:
Excellent corrosion resistance to various corrosive media in oxidizing and reducing environments
Excellent resistance to pitting and crevice corrosion, and no stress corrosion cracking due to chlorides
Excellent corrosion resistance to inorganic acids, such as nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid, and mixed acids of sulfuric acid and hydrochloric acid, etc.
Excellent corrosion resistance to various inorganic acid mixed solutions
When the temperature reaches 40ºC, it can show good corrosion resistance in various concentrations of hydrochloric acid solution
Good workability and weldability, no post-weld cracking susceptibility
Manufacture certification of pressure vessels with wall temperature of -196~450ºC
1.2, application field
Parts of organic chemical process processes that contain chlorides, especially where acidic chloride catalysts are used
Digesters and bleaching tanks for the manufacture of pulp and paper industries
Absorption tower, reheater, flue gas inlet baffle, fan (humid), agitator, deflector and flue, etc. in the flue gas desulfurization system
For the manufacture of equipment and components for use in sour gas environments
The reaction between acetic acid and acetic anhydride
Similar grades, chemical compositions and standards
2.1, similar grades
UNS NO6625 Inconel625 (USA), NC22DNb (France), /.Nr.2.4856 (Germany)
2.2. Implementation standards
GJB 1953-1994 "Specification for hot-rolled hot-rolled bars of superalloy for rotating parts of aero-engine"
GJB 2611-1996 "Specification for cold-drawn rods of superalloys for aviation"
GJB 2612-1996 "Specification for high temperature alloy cold drawing wire for welding"
GJB 3020-1997 "Specification for superalloy ring blanks for aviation"
GJB 3165-1998 "Specification for hot-rolled and forged bars of superalloys for aerospace load-bearing parts"
GJB 3782-1999 "Specification for superalloy rods for aviation"
HB 5198-1982 "Deformed Superalloy Bars for Aviation Blades"
physical properties
3.1. Density
ρ=8.4g/cm3
3.2. Melting temperature
1290~1350ºC
Metallographic structure
The alloy has a face-centered cubic lattice structure. When held at about 650°C for a sufficient time, carbon particles and an unstable quaternary phase will precipitate and transform into a stable Ni3(Nb,Ti) orthorhombic 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 decrease.
Machining and Heat Treating
5.1. Process performance and requirements:
GH3625 (GH625) alloy can be manufactured and processed by traditional production processes, and is suitable for cold and hot processing and machining, but due to its high strength, high-power processing equipment is required for cold and hot processing.
5.2. Heating
1. The workpiece should always be kept clean before and during the heat treatment.
2. Do not contact sulfur, phosphorus, lead and other metals with low melting point during heat treatment, otherwise the material will become embrittled. Attention should be paid to removing dirt such as marking paint, temperature indicating paint, colored crayons, lubricating oil, fuel, etc.
3. The lower the sulfur content in fuel, the better. The sulfur content in natural gas should be less than 0.1%, the sulfur content in city gas should be less than 0.25g/cm3, and the sulfur content in heavy oil should be less than 0.5%.
4. Considering the needs of temperature control and keeping clean, it can be heated in an electric heating furnace, or a gas heating furnace with pure gas can be used.
5. It can also be heated in a box furnace or gas furnace, but the furnace gas must be clean and suitable for neutral to slightly oxidizing properties. It should be avoided that the furnace gas fluctuates between oxidizing and reducing properties. artifact.
5.3. Thermal processing
1. The hot working temperature range of GH3625 (GH625) is 1150ºC~900ºC, and the cooling method is water quenching or other rapid cooling methods.
2. In order to obtain the best performance and corrosion resistance, annealing treatment should be carried out after hot working.
3. When heating, the material can be directly sent to the furnace that has been heated to the highest working temperature, and after sufficient heat preservation time (60 minutes of heat preservation time per 100mm thickness), the furnace is quickly released, and hot processing is carried out in the high temperature section of the specified temperature range. When the material temperature drops below the thermal processing temperature, reheating is required.
5.4, cold working
1. The cold working material should be in the annealed state, and the work hardening rate is larger than that of austenitic chromium-nickel stainless steel, so it is necessary to select the processing equipment.
2. During cold working, intermediate annealing is required.
3. When the processing amount is more than 15%, annealing treatment should be carried out after hot working.
5.5 Descaling and pickling
The surface oxides of the alloy and the welding slag around the weld have stronger adhesion than low alloy stainless steel, and it is recommended to use a fine-grained abrasive belt or a fine-grained grinding wheel for grinding.
GH3625 Chemical composition
(GB/T14992-2005)
alloy grade % Ni Cr Fe Nb Mo Co C Mn Si S P Cu Al Ti
GH3625 minimum margin 20.0 3.15 8.0
maximum 23.0 5.0 4.15 10.0 1.0 0.10 0.5 0.5 0.015 0.015 0.07 0.4 0.4
GH3625 Physical performance
density melting point Thermal conductivity specific heat capacity Elastic Modulus Shear modulus Resistivity Poisson's ratio Linear expansion coefficient
g/cm3 °C λ/(W/m·ºC) J/kg·ºC GPa GPa μΩ·m a/10-6ºC-1
8.44 1290 -1350 12.1(100ºC) 430 205 79 1.28 0.308 12.3(20~100ºC)
GH3625 Mechanical Properties
(Minimum value of mechanical properties measured at 20°C [1] )
Heat treatment method tensile strength Yield Strength Elongation Brinell hardness
σb/MPa σp0.2/MPa σ5 /% HBS
Solution treatment 830 410 30 ≤290
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