Research Progress of Nickel-based Corrosion Resistant Alloys
Nickel-based alloys not only have unique corrosion resistance and even high temperature corrosion resistance in many industrial corrosive environments, but also have high strength, good plasticity and toughness. They can be smelted, cast, cold and hot deformation, processing and welding, and are widely used in petrochemical, energy, marine, aerospace and other fields.
1. Composition and Classification
Nickel is completely stable in alkali solution and has excellent corrosion resistance to active gases (such as fluorine, chlorine, bromine and their hydrides), hydroxides (such as NaOH, KOH) and some organic compounds. The main role of alloying elements in resisting corrosion in aqueous solution of nickel-based alloys is shown in Table 1.
Table 1 effect of elements in nickel-based alloys
The results show that the effect of alloying elements on improving corrosion resistance of alloys comes from the stability of passive film formed on the surface of nickel alloys. The content of nickel in nickel-based alloys is more than 30%. Among them, W(Ni+Fe)>50% is called iron-nickel-based corrosion-resistant alloy, W(Ni)>50% is called nickel-based corrosion-resistant alloy, which can be considered as nickel-based corrosion-resistant alloy in practical use. Its classification is shown in Table 2.
Table 2 Variety nickel-based corrosion resistant alloys
2. Performance and Application
Fig. 1 A family of nickel-based corrosion-resistant alloys.
2.1 Ni-Cu System
Ni and Cu can be mixed in any proportion to form solid solution alloys, known as Monel alloys. Ni-Cu has good resistance to HF, seawater brine and crevice corrosion. Monel alloy Ni70Cu30 is the earliest nickel-based corrosion resistant alloy. It not only has high strength and toughness, but also has excellent corrosion resistance to reducing acid and strong alkali medium and sea water. It is usually used to manufacture equipment for transporting hydrofluoric acid (HF), brine, neutral medium, alkali salt and reducing acid medium.
Monel alloys can be divided into cast alloys and deformed alloys.
Monel alloy is widely used in corrosion-resistant pipe fittings, flanges, pipelines and naval ships abroad. For example, the fastener bolts and nuts used in the North Sea Oil Pipeline and the Thames River Bridge in Britain are used by the combination of Monel 400 and Monel K500; parts of the key shaft and pump parts in the propeller of a class of British ships are made of Monel alloy; and many equipment and systems of the French “de Gaulle” aircraft carrier are made of Mo. Nel material. Monel alloys are even used on the roofs of some buildings in the United States, such as the Pennsylvania Railway Station, the Brooklyn Museum of Art and Sciences, the National Gallery of Art, the Pentagon, etc.
2.2. Ni-Cr, Ni-Fe-Cr systems
In Ni-Cr-Fe system, Inconel alloy has lower Fe content and Incoloy alloy has higher Fe content. Incoloy alloys are actually Fe-Ni-Cr alloys in nickel-based alloys because of their high Fe content of 45%. The cast alloy of Inconel alloy is CY240 and the rolling grade is Ineonel 600. Ineoloy alloy rolling plate number is Incoloy 800 alloy. In the current corrosion-resistant nickel-based alloys, their application in valve production is second only to Monel alloy.
Typical Ni-Cr corrosion resistant alloys are Inconel 600 (domestic brand 0Cr-15Ni75Fe). It is resistant to both high temperature and corrosion. Inconel 690 (0Cr30Ni60Fe) has been widely used in chemical industry due to its improved stress corrosion resistance and intergranular corrosion resistance.
2.3. HasteIloy High Corrosion Resistant Alloys
Ultra-low carbon Ni-Cr-Mo alloys with Cr and Mo as main alloying elements are also called Hastelloy alloys. Hastelloy is the trademark of Haynes International Company in the United States. It consists of HA in HAYNES, STELL in STEI. LITE and OY in ALLOYS. As a high-grade nickel-based alloy, Hastelloy has excellent corrosion resistance to various adverse corrosion environments, such as wet oxygen, sulfite, strong oxidant medium, etc.
Harrington alloys are mainly A, B, C, D, F, G, N, W, X series. The main international companies producing Hastelloy series alloys are Haynes International Inc. (Hans International Inc., R&D company of Hastelloy series alloys), Special Metal (Superalloy Group) and ThyssenKrupp Company of Germany.
Harrington alloys used in chemical plants are mainly B, C and G. The mechanical properties of these three kinds of Hastelloy alloys are shown in Table 5.
Table 5 Mechanical properties of Hastelloy alloys
(1) Hastelloy B
Series B includes B, 132 and B3. Hastelloy B alloy has the best hydrochloric acid corrosion resistance. Hastelloy B-2 alloy is formed by reducing carbon content to 0.02% and Si content to 0.1%. It can be used in any concentration of hydrochloric acid at boiling temperature, and improves the intergranular corrosion resistance in sensitized and post-welded states.
In the 1990s, the invention of Hastelloy B-3 completely changed the disadvantage that B-2 easily precipitated Ni-Mo precipitates when passing through the intermediate temperature, and improved the processing performance. However, Hastelloy B and Hastelloy B-2 alloys have very low Cr content and can not be used in oxidizing environment.
(2) Hastelloy C
Hastelloy C is a Ni-Cr-Mo series, which is a general corrosion resistant material suitable for various environments. C series has a high degree of alloying. The elements of Cr and Mo play the role of resisting the corrosion of oxidizing and reducing media respectively, and jointly play the role of resisting the local corrosion (pitting and crevice corrosion).
C series have C, C-276, C-4, C-22, C-2000. In the 1930s, Hastelloy C, the first C-276 in the 1960s, C-4 in the 1970s, C-22 in the 1980s, 59, 686, C-2000 in the 1990s, etc.
Intergranular corrosion, local corrosion, stress corrosion and passivation behavior of Ni-Cr-Mo alloys were studied by electrochemical methods abroad. The S Ghosh study shows that C-276 has better corrosion resistance than UNS N08367 and UNS N08028 alloys in NaCl and H3PO4 solutions at 95 C.
(3) Hastelloy G
Hastelloy G is Ni-Cr-Cu-Mo system. Ni_Cr_M0-Cu alloy containing Cu is more resistant to corrosion of sulfuric acid and phosphoric acid than Ni-Cr-Mo alloy. Ni-Cr-Mo-Cu alloy with high Cr content has good corrosion resistance in sulfuric acid, phosphoric acid, sulfuric acid containing F-, Cl-, phosphoric acid and wet-process phosphoric acid. Adding Si and B to Ni-Cr-Mo-Cu alloy can resist concentrated sulfuric acid corrosion with high hardness and good wear resistance.
G series has G, G-3, G-30, G-50 and so on. Hastelloy G-3 and G-30 alloys have been developed to solve the problem of their application in strong oxidizing or mixed acid environments. The new Hastelloy G-35 is essentially a Ni-Cr-Mo alloy with a composition similar to that of the C-series alloy.
Because its invention is still designed for strong oxidation and mixed acid environment, the commercial brand is still classified as G series.
3. R&D process
3.1 International Overview
In 1906, patents 811 and 239 of the United States gave the production method of Monel 400 alloy, which is considered to be the earliest nickel-based corrosion resistant alloy. In 1914, the United States began to produce Ni-Cr-Mo-Cu corrosion-resistant alloys; in 1920, Germany began to produce Ni-Cr-Mo corrosion-resistant alloys containing about 15% Cr and 7% Mo.
In 1930, Haynes International Company developed Ni-Mo alloy B and Ni-Cr-Mo alloy C.Ni alloy. The next important stage of development came from Inco Company. In 1931, Ni-Cr-Fe alloy 600 was developed. In 1949, Ni-Fe-Cr alloy was developed, named Ineonel and Incoloy respectively. In the 1970s, nearly 50 kinds of corrosion resistant alloys were produced in various countries. There are more than 10 kinds of alloys, such as Ni-Cu, Ni r, Ni-Mo, Ni-Cr~Mo (W), Ni-Cr-Cu, Ni-Fe-Cr and Ni-Fe-Cr-Mo, which have large output and wide application. In the 1970s and 1980s, the properties of corrosion-resistant alloys have made a breakthrough.
F Galen Hodge summarizes the development of the first, second and new generation alloys.
Mitsubishi Material Corporation of Japan has developed a new alloy MAT21 with better corrosion resistance than C-276. Its composition is Ni60%-Crl9%-M019%-Til.8%. The weight loss caused by corrosion in severe corrosive environments such as hydrochloric acid, nitric acid and phosphoric acid is only 1/3-1/10 of that of nickel-based alloys. Haines International Company applied for “sulfuric acid resistance and wet process” in China in 2003. Ni-Cr-Mo-Cu alloy of phosphoric acid “patent”. This alloy is better than C-276, which is the most sulfuric acid-resistant alloy at present. It has better resistance to wet-process phosphoric acid than alloy A in N0.5424029, which is the most wet-process phosphoric acid-resistant alloy in the United States.
3.2. Overview of China
Since the 1950s, our country began to imitate and improve foreign nickel-based alloys. By the end of 1970s, there were more than 10 brands. Since the 1980s, considerable progress has been made in the development of nickel-based alloys with some new brands. In 1984, Chongqing Instrument Materials Research Institute developed Ni-Cr-Mo corrosion-resistant alloy named 3YC24 alloy according to the requirement of corrosion-resistant alloy for industrial process detection and control instruments under harsh environment. In 1986, the General Institute of Iron and Steel Research invented a nickel-based corrosion-resistant alloy suitable for severe corrosive environments such as boiling hydrofluoric acid, vapor phase and wet chlorine, wet fluorine, hydrochloric acid and sulfuric acid. Especially in boiling hydrofluoric acid, the corrosion resistance of the alloy is 100 times higher than that of Hastelloy C-4 and Hastelloy C-267. In 1994, 23 nickel-based corrosion-resistant alloys and 24 superalloys were published.
Monel alloy is seldom used in China, especially Monel alloy valves are almost imported. Jinzhou Ferroalloy Co., Ltd. has developed Monel alloy which can replace imported products. Inconel 600 is still in its initial stage of production and application in China, and its application is limited to a few imported equipment and parts. The fluorination project of Zhejiang Yazhou Chenhua (Group) Company, which was constructed by China Chemical Engineering 14th Construction Company, adopts in-conel 600 alloy pipeline imported from the United States in some process pipelines. In order to break the monopoly of developed countries, Sichuan Chuantou Great Wall Special Steel Co., Ltd. has successfully developed the plates and pipes of corrosion resistant alloys Incoloy 800, Incoloy 800H, Inconel 625, Inconel 690 and NSl41.
Nickel-based corrosion-resistant alloys are more and more widely used in industrial fields because of their good mechanical properties, processing properties and corrosion resistance. China has abundant nickel resources. With the rapid economic development, nickel alloys will maintain strong demand. Therefore, the research and development of nickel-based alloys is of great economic and practical significance for making full use of the advantages of nickel and cobalt resources of Jinchuan Group Company, expanding the product field of the company’s special alloy material factory, enhancing the ability of enterprises in the field of deep processing of nickel alloy products, and expanding the market coverage of products. The author believes that the future research of nickel-based corrosion resistant alloys should be strengthened in the following aspects.
- (1) The development of new nickel-based corrosion resistant alloys should be accelerated, and the research on their application fields should be strengthened.
- (2) Aiming at the engineering field, the key technological parameters such as shaping, welding and heat treatment of relevant industrial equipment manufacturing are studied in depth.
- (3) Study more complex and harsh corrosion behavior and mechanism.
Source: China Welded Joints Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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