INCONEL 625 alloy (UNS NO 6625) INCONEL 625 chemical composition and implementation standards
Alloy 625 (UNS 6625) is an austenitic super heat-resistant alloy with nickel as the main component. It has excellent properties of extensive resistance to oxidation and corrosion, and is suitable for use in jet aircraft engine environments, aviation, and chemical processing. Many fields. The alloy also has extraordinary fatigue resistance at temperatures as low as 2,000 degrees Fahrenheit (1,093 degrees Celsius). The strength of 625 alloy comes from the solid solution strengthening effect of molybdenum and niobium contained in the nickel-chromium alloy. These elements also give the alloy excellent corrosion-resistant properties. While the alloy is designed for strength in high-temperature environments, its highly alloyed composition gives it a high degree of resistance to general corrosion as well as resistance to a wide range of oxidizing and non-oxidizing environments. The chromium and molybdenum content make the alloy excellent in resisting corrosion spots caused by chloride ions.
Characteristics, high nickel content enhances the alloy's resistance to chloride stress corrosion cracking. The material is highly formable and easier to weld than many nickel-based alloys. Even when being welded, the alloy remains resistant to intergranular corrosion.
Corrosion and oxidation resistance
The high content of chromium and titanium in alloy 625 provides the alloy with a high degree of resistance to pitting corrosion and fission corrosion. It has anti-corrosion effects in chloride-contaminated media, such as seawater, neutral salts and salt water. The alloy is resistant to a wide range of corrosive media ranging from highly oxidizing environments to moderately mitigated oxidizing environments. Geothermal salt water test results show that 625 alloy has extremely high resistance to geothermal water, and its corrosion resistance is comparable to secondary titanium. Simulated pipeline gas desulfurization environmental tests show that 625 alloy has extremely high corrosion resistance compared with 316L material, and its corrosion resistance is comparable to 276 alloy.
Antioxidant properties
Alloy 625 has excellent properties of resistance to oxidation and phosphorus-like corrosion in high temperatures up to 2000 degrees Fahrenheit (1093 degrees Celsius). Under cyclic heating and cooling conditions, 625 alloy outperforms other high-temperature resistant alloys.
Inconel625 processing application
Thermal processing:
1. The thermal processing temperature range of Inconel625 is 1150℃~900℃, and the cooling method is water quenching or other speed 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 fed into the furnace that has been heated to the maximum working temperature. After being kept warm for a sufficient time (60 minutes of holding time is required for each 100mm thickness), it can be quickly released from the furnace and thermally processed in the high temperature section of the specified temperature range. When the material temperature drops below the thermal processing temperature, it needs to be reheated.
Cold working:
1. Cold-worked materials should be in an annealed state. The work hardening rate of Inconel 625 is greater than that of austenitic chromium-nickel stainless steel, so processing equipment needs to be selected.
2. During cold working, intermediate annealing is required.
3. When the processing volume is greater than 15%, annealing treatment must be performed after hot processing.
Scale removal and pickling:
1. The surface oxide of Nicrofer6020hMo alloy and the adhesion of the welding slag around the weld are stronger than that of low-alloy stainless steel. It is recommended to use a fine-grained abrasive belt or fine-grained grinding wheel for grinding.
2. The oxide film must be broken up by careful grinding or salt bath pretreatment before pickling with H NO 3/HF mixed acid at appropriate time and temperature.
machining
Inconel 625 should be machined after heat treatment. Due to the work hardening of the material, it is preferable to use a lower alloy than machined
Standard austenitic stainless steels are machined with low cutting speeds and heavy feeds to get under the work-hardened surface.
welding
Inconel 625 is suitable for welding using any traditional welding process, such as tungsten electrode inert gas shielded welding, plasma arc welding, manual sub-arc welding, metal pole inert gas shielded welding, and melting pole inert gas shielded welding. The materials to be welded should be in a solution-treated state to remove scale, oil stains and various marks and marks. Welding operations should be performed under specified low heat input, with the interpass temperature not exceeding 150°C. Heat treatment before and after welding is no longer required.
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