(I) Corrosion resistance
Inconel 625 alloy has excellent performance in corrosion resistance and can easily cope with a variety of corrosive media. In the face of acidic media, such as nitric acid, hydrochloric acid, sulfuric acid, etc., and their mixed acids, the alloy shows an extremely low corrosion rate. For example, in 10% nitric acid (oxidizing acid), its corrosion rate is only 0.25mm/year, and in 10% hydrochloric acid (reducing acid), the corrosion rate is 0.45mm/year; in a high concentration of sulfuric acid environment, a passivation film can be formed on the surface of the alloy to effectively prevent the invasion of corrosive ions. In alkaline media, it also has good corrosion resistance and can maintain its own stable performance.
For highly corrosive media such as high concentrations of CO₂ and H₂S, Inconel 625 alloy is not inferior. In chloride-containing media, it has excellent resistance to pitting, crevice corrosion, intergranular corrosion and erosion, and can effectively resist chloride ion reduction stress corrosion cracking. Even in complex environments such as seawater containing a large amount of chloride ions, even after exposure for 6000 hours, its corrosion depth is only 0.005mm, which is much better than ordinary stainless steel, and it will hardly corrode when in contact with salt solutions at high temperatures.
It is precisely with this excellent corrosion resistance that Inconel 625 alloy is widely used in many fields. In the chemical industry, it is often used to manufacture equipment and pipelines working in various corrosive media, such as reactors, heat exchangers, pumps and valves, etc., to ensure that the equipment can operate stably for a long time and reduce the frequency of maintenance and replacement; in the field of marine engineering, components such as desalination plant equipment and offshore oil production equipment that face the threat of seawater corrosion can effectively resist seawater erosion and operate reliably.
(II) High temperature performance
Inconel 625 alloy has good performance from low temperature to high temperature environment (such as around 980℃). In low temperature environments, its mechanical properties remain stable and reliable, and as the temperature rises, the advantages of the alloy become more prominent.
At high temperatures, it has good tensile properties and can withstand large tensile forces without breaking. Its fatigue properties are also excellent.
Even under repeated stress conditions, such as when aircraft engine parts are constantly started and stopped and subjected to alternating stress during operation, the alloy can maintain a good performance state and is not prone to fatigue cracks, ensuring safety and life. Its creep resistance is a highlight. Under high temperature and high stress conditions, its deformation behavior is slow. For example, under conditions of 800°C and 500 MPa, the creep rate is 0.01% per hour, and the reliable creep life can reach more than 100,000 hours, which is suitable for long-term high-load working environments.
For this reason, Inconel 625 alloy has key applications in high-temperature scenarios such as aerospace engines, such as for the manufacture of high-temperature engine parts, combustion chambers, nozzles, etc. In these high-temperature and performance-demanding parts, the alloy can work stably to ensure the normal operation of aerospace equipment.
(III) Antioxidation Performance
Inconel 625 alloy has excellent oxidation resistance, which is mainly due to the synergistic effect of various elements in its chemical composition. Among them, chromium will form a dense chromium oxide film on the surface of the alloy at high temperature. This film can effectively prevent the penetration of oxidizing substances such as oxygen and prevent the internal metal from being further oxidized. Nickel gives the alloy good basic oxidation resistance, so that it can maintain its own performance stability in an oxidizing environment. At the same time, elements such as molybdenum and niobium also indirectly contribute to the oxidation resistance of the alloy and improve the overall oxidation resistance.
Inconel 625 alloy prepared under different processes has certain differences in oxidation resistance. For example, Inconel 625 that has been solution treated can restore the crystal structure in the material to a uniform austenite structure, making the oxidation resistance film denser and forming a better protective layer, which can effectively prevent the erosion of oxygen and other corrosive gases; while the density and adhesion of the oxidation film of Inconel 625 after aging treatment are slightly inferior to those of the material after solution treatment at above 600°C, but the overall comprehensive performance is still excellent.
In high-temperature oxidizing environments, the application advantages of Inconel 625 alloy are obvious. For example, when used in high-temperature components in the aerospace field, high-temperature reactors in the chemical industry and other equipment, even if it is in a high-temperature environment for a long time and may be exposed to oxidizing substances, it can extend the service life of the equipment with its good anti-oxidation properties, and reduce performance degradation and structural damage caused by oxidation.
(IV) Mechanical properties
The tensile strength of Inconel 625 alloy is relatively good, and the tensile strength can reach 830MPa or above at room temperature. In a high-temperature environment, it can also maintain a high tensile strength level within the corresponding temperature range to ensure that it is not easy to be broken when subjected to tension. In terms of yield strength, it is usually ≥415 MPa, which means that it can maintain a stable shape and performance before the force reaches a certain level, and plastic deformation will not easily occur.
In terms of hardness performance, like HB 170-215, it has a certain hardness foundation, which can meet the needs of different processing and use scenarios. The elongation can reach 30% or more at room temperature, showing good ductility. Even in high temperature environments, such as 600°C, the elongation can reach more than 20%. At the extreme temperature of 900°C, the elongation can be maintained at about 10%, enabling it to withstand large plastic deformation and not prone to brittle fracture; the cross-sectional shrinkage can also be maintained at a reasonable level to ensure the stability of the material's performance under tension and other conditions.
Different processing conditions have a significant impact on these properties. During hot working, the temperature range is generally between 1150°C and 900°C. If annealing and other appropriate process operations are performed after hot working, the performance can be optimized and the corrosion resistance can be improved; during cold working, because its work hardening rate is greater than that of austenitic chromium-nickel stainless steel, when the processing volume is large, intermediate annealing and other operations are required to restore toughness and plasticity to avoid excessive work hardening leading to increased brittleness and affecting the alloy's original good mechanical properties.
