Asme Best Corrosion-Resistant Nickel Alloys Inconel 625 Heat Exchanger/Condenser Tubes
Inconel nickel chromium alloy 625 is used for its high strength, excellent fabricability (including joining), and outstanding corrosion resistance Service temperatures range from cryogenic to 1800F.
Strength of Inconel alloy 625 is derived from the stiffening effect with molybdenum and columbium on its nickel-chromium matrix, thus hardening treatments are not required. This combination of chemical elements also is responsible for superior resistance to a wide range of corrosive environments of unusual severity as well as to high-temperature effects such as oxidation and carburization.
The inconel 625 versatile and outstanding corrosion resistance under a wide range of temperatures and pressures is a primary reason for its wide acceptance in the chemical processing field. Because of its ease of fabrication, it is made into a variety of element and component for plant equipment. Its high strength enables it be used, for example, in thinner-walled vessels or tubing than possible with other materials, thus improving heat transfer and saving weight. Some applications requiring the combination of corrosion resistance and strength offered by Inconel alloy 625 are tubing, reaction vessels, distillation columns, heat exchangers, transfer piping and valves.
Features: Inconel 625 has excellent strength at temperatures up to 816℃. At higher temperatures, its strength is generally lower
than that of other solid solution strengthened alloys. Inconel 625 has good oxidation resistance at temperatures up to 980℃ and
shows good resistance to aqueous corrosion, but is relatively moderate compared to other more capable corrosion resistant alloys.
Applications: Chemical process industry and sea water application. Inconel 625 is used in short term applications at temperatures
Many metals are also used in heat exchangers, especially for industrial applications and mechanical uses. There are a lot of considerations that a design engineer needs to take into consideration when it comes to material selection for heat exchangers and its components.
This includes considering the pressure that components will be subjected to, the temperature ranges of operation, the fluids in the system, the ease of maintenance and repair, and the capacity required. Of course, cost is also a primary factor in material selection for large-scale projects.
While metals such as copper, aluminium, carbon steel, stainless steel and titanium are all popular choices, when it comes to the most corrosive and challenging environmental conditions, nickel alloys are often used due to their strength, corrosion resistance, high-temperature resistance and longevity.
There are a number of high-performance nickel alloys that can be employed in heat exchangers across different industrial applications. These are usually provided as pipes or tubes in a choice of different materials, some of which we have outlined below.
Inconel nickel-chromium-iron alloy 600 is a engineering material which require resistance to corrosion and heat. The alloy also has superb mechanical properties and presents the desirable combination of high strength and good workability. The high amount of nickel content gives the alloy resistance to corrosion by many organic and inorganic compounds and also makes it virtually immune to chloride-ion stress-corrosion cracking. Chromium confers resistance to sulfur compounds and also provides resistance to oxidizing conditions at high temperatures or in corrosive solutions. The alloy is not precipitation hardenable, it is strengthened and hardened only by cold work.
The Inconel alloy 600 is versatility has led to its use in a variety of manufaturing applications involving temperatures from cryogenic to above 2000F. The alloy is used extensively in the chemical industry like pharmacutical for its strength and corrosion resistance. Applications include bubble towers, stills, heaters, and condensers for processing of bubble towers, fatting acids, evaporator tubes, tube sheets, and flaking trays for the manufacture of sodium sulfid, and equipment for handling abietic acid in the manufacture of paper pulp.
The alloy's strength and oxidation resistance at high temperatures make it useful for many applications in the heat treating industry. It is used for retorts, muffles, roller hearths, and other furnace components and for heat treating baskets and trays. In the aeronautical field, alloy 600 material is used for a variety of engine and airframe components, which must withstand high temperatures. Examples are lock wire, exhaust liners, and turbine seals.
The alloy is also a standard material of constructing nuclear reactors. It has excellent resistance to corrosion by high purity water, and no indication of chloride-ion stress-corrosion cracking in reactor water systems has been detected. For nuclear applications, the alloy is produced to exacting specifications and is designated Inconel alloy 600T.
Incoloy alloy 800 is a widely used material of construction for equipment that must have high strength and resist carburization,oxidation and other harmful effects of high-temperature exposure. (For high temperature applications requiring optimum rupture and creep properties, Incoloy alloys 800H and 800HT are used). The chromium in the alloy imparts resistance to oxidation and corrosion. The high percentage of nickel maintains an austenitic structure so that the alloy is ductile. the nickel content also contributes general corrosion, resistance to scaling and stress-corrosion cracking.
Incoloy alloy 800 is used in a variety of applications involving exposure to high temperatures and corrosive environments. It is used for heat-treating equipment such as baskets, trays and fixtures. In chemical and petrochemical processing the alloy is used for heat exchangers and other piping systems in nitric acid media especially where resistance to chloride stress-corrosion cracking is required. In nuclear power plants, it is used for steam-generator tubing. The alloy is often used in home appliances for sheathing of electric heating elements. In the production of paper pulp, digester liquid heaters are often made of alloy 800. In petroleum processing , the alloy is used for heat exchangers that air-cool the process stream.
- Resistance to prolonged exposure to elevated temperatures
- Excellent resistance to oxidation, sulfidation, and carburization
- Added Carbon and annealing treatment allows for higher creep and rupture properties above 1100°F (600°C)
- Resistant to high temperature corrosion
- Readily machined by standard methods
- Best joined/welded using products for high temperature situations
- Resistance to aqueous corrosion at moderate temperature
Incoloy alloy 825 is a nickel-iron-chromium alloy with additions of copper, molybdenum and titanium. The alloy's chemical composition is designed to provide exceptional resistance to many corrosive environments. The nickel content is sufficient for resistance to chloride-ion stress corrosion cracking. The nickel, in conjunction with the molybdenum and copper, also gives outstanding resistance to reducing environments such as those containing sulfuric and phosphoric acids. the molybdenum also aids resistance to pitting and crevice corrosion. The alloy's chromium content confers resistance to a variety of oxidizing substances such as nitrates, nitric acid and oxidizing salts. The titanium addition serves, with an appropriate heat treatment, to stabilize the alloy against sensitization to intergranular corrosion. The resistance of Incoloy 825 to general and localized corrosion under diverse conditions gives the alloy broad usefulness. Applications include chemical processing, pollution control, oil and gas recovery, acid production, pickling operations, nuclear fuel reprocessing and handling of radioactive wastes.