Nickel-based alloy

Parameter

Description

Nickel-based alloys are a group of alloys that exhibit excellent strength and good oxidation and corrosion resistance at high temperatures (650 to 1000 degrees Celsius). These alloys can be further classified according to their main functional properties, including nickel-based heat resistant alloys, nickel-based corrosion resistant alloys, nickel-based wear resistant alloys, nickel-based precision alloys and nickel-based shape memory alloys. In the category of superalloys, according to the main composition, it can be divided into iron, nickel and cobalt based superalloys, of which nickel-based superalloys are usually referred to as nickel-based alloys.

The main elements of corrosion resistant alloys include copper, chromium and molybdenum, which have excellent combined properties and can resist a variety of acidic environments and stress corrosion. The earliest corrosion resistant alloy was the nickel-copper alloy produced in the United States in 1905, which is the famous Monel alloy (the composition ratio of Ni 70 Cu30). In addition, there are nickel-chromium alloy (that is, nickel-based heat-resistant alloy, which is also a heat-resistant corrosion alloy in corrosion resistant alloy), nickel-molybdenum alloy (mainly Hastelloy B series), nickel-chromium molybdenum alloy (mainly Hastelloy C series) and so on. Pure nickel is also a typical representative of nickel-based corrosion resistant alloys. These alloys are widely used in the manufacture of components for corrosion-resistant environments in industries such as petroleum, chemical and power.

Nickel-based corrosion resistant alloys usually have an austenitic structure. After solution and aging treatment, there will be intermetallic phase and metallic carbon nitride in austenitic matrix and grain boundary. Corrosion resistant alloys with different compositions can be divided into the following categories according to their characteristics:

The corrosion resistance of Ni-Cu alloy is better than that of pure nickel in reducing medium and better than that of pure copper in oxidizing medium. In the absence of oxygen or oxidant environment, it is the best material to resist high temperature fluorine, hydrogen fluoride and hydrofluoric acid.

Ni-Cr alloy, that is, nickel-based heat resistant alloy, is mainly used in oxidizing media. It can resist high temperature oxidation and corrosion of gases containing sulfur and vanadium, and its corrosion resistance increases with the increase of chromium content. These alloys also have good resistance to hydroxide (such as NaOH, KOH) corrosion and stress corrosion.

Ni-Mo alloy is mainly used in reducing medium corrosion conditions, it is one of the best alloys to resist hydrochloric acid corrosion, but in the presence of aerobic and oxidizing agents, its corrosion resistance will be significantly reduced.

Ni-cr-mo (W) alloy has the characteristics of both Ni-Cr alloy and Ni-Mo alloy, and is mainly used in REDOX mixed media. This kind of alloy shows good corrosion resistance in high temperature hydrogen fluoride gas, in hydrochloric acid and hydrofluoric acid solution containing oxygen and oxidant, and in wet chlorine gas at room temperature.

Ni-Cr-Mo-Cu alloy has the ability to resist nitric acid and sulfuric acid corrosion, and also shows good corrosion resistance in some oxidation-reducing mixed acids.

Nickel-based alloys have a wide range of applications, including:

Marine field: Marine structures, seawater desalination, mariculture, seawater heat exchange, etc.

Environmental protection: flue gas desulfurization equipment for thermal power generation, wastewater treatment, etc.

Energy field: nuclear power generation, comprehensive utilization of coal, tidal power generation, etc.

Petrochemical field: oil refining, chemical equipment, etc.

Food field: salt production, soy sauce brewing, etc.

In these special areas, ordinary stainless steel 304 often cannot meet the requirements, and special stainless steel is indispensable. In recent years, with the rapid economic growth and the continuous upgrading of the industrial field, more and more projects require higher performance stainless steel. With the growth of demand for nickel-based alloys in various industries, the market size of nickel-based alloys in China reached 23.07 billion yuan in 2011, with a year-on-year growth rate of 19.47%, showing that the industry is in a steady upward trend.