nickel based alloys is a kind of alloy with high strength and certain oxidation resistance and corrosion resistance at high temperature of 650 ℃. According to the main properties, it can be divided into nickel base heat resistant alloy, nickel base corrosion resistant alloy, nickel base wear resistant alloy, nickel base precision alloy and nickel base shape memory alloy. According to the matrix, the superalloy can be divided into Fe base superalloy, nickel base superalloy and cobalt base superalloy. Nickel-based superalloys are referred to as nickel-based alloys.
The main alloying elements are copper, chromium and molybdenum. With good comprehensive performance, can withstand various acid corrosion and stress corrosion. The earliest application (produced in 1905 in America) was nickel-copper (Ni-Cu) alloy, also known as Monel alloy (Monel alloy Ni 70 Cu30). In addition, there are nickel-chromium (Ni-Cr) alloys (that is, nickel-based heat-resistant alloys, heat-resistant corrosion alloys in corrosion-resistant alloys) and nickel-molybdenum (Ni-Mo) alloys (mainly referred to as Hardite alloy B series). Nickel-chromium-molybdenum (Ni-Cr-Mo) alloy (mainly refers to the Hashi alloy C series) and so on. At the same time, pure nickel is also corrosion resistant based on nickel. A typical representation in an alloy. These nickel-based corrosion-resistant alloys are mainly used in the manufacture of petroleum, chemical, electrical and other corrosion-resistant environmental components.
Nickel-based corrosion-resistant alloys have austenitic structures. In the state of solid solution and aging treatment, the austenitic matrix and grain boundary of the alloy also have intermetallic phase and metal carburide. The corrosion resistant alloys are classified according to their composition and their properties.
The corrosion resistance of Ni-Cu alloy is better than that of nickel in reducing medium and that of copper in oxidizing medium. It is the best material for high temperature resistance to fluorine, hydrogen fluoride and hydrofluoric acid (see metal corrosion) under the condition of no oxygen and oxidant.
Ni-Cr alloy is nickel-based heat-resistant alloy; mainly used in oxidizing medium. Resistance to high temperature oxidation and corrosion of gases such as sulfur and vanadium increases with the increase of chromium content. The alloys also have good resistance to hydroxide (such as NaOH,KOH) corrosion and stress corrosion resistance.
Ni-Mo alloy is mainly used in the condition of reducing medium corrosion. It is the best alloy for hydrochloric acid corrosion resistance, but the corrosion resistance decreases significantly in the presence of oxygen and oxidant.
Ni-Cr-Mo (W) alloy has the properties of Ni-Cr alloy and Ni-Mo alloy. It is mainly used in redox mixed medium. This kind of alloy has good corrosion resistance in high temperature hydrogen fluoride gas, hydrochloric acid solution containing oxygen and oxidant, hydrofluoric acid solution and wet chlorine gas at room temperature.
Ni-Cr-Mo-Cu alloy has the ability to resist both nitric acid and sulfuric acid corrosion, and also has good corrosion resistance in some redox mixed acids.
Nickel-based alloys are found in many fields, such as:
1. Ocean: ocean structure, desalination, mariculture, marine heat exchange, etc.
2. environmental protection field: flue gas desulfurization device for thermal power generation, wastewater treatment and so on.
3.Energy field: atomic power generation, comprehensive utilization of coal, tidal power generation and so on.
4. petrochemical field: refining, chemical and chemical equipment, etc.
Food field: salt making, soy sauce brewing, etc. In many fields above, ordinary stainless steel 304 is incompetent, in these special fields, special stainless steel is indispensable and irreplaceable.