Titanium alloy refers to various alloy metals made of titanium and other metals. Titanium is an important structural metal that developed in the 1950s. Titanium alloys have high strength, good corrosion resistance, and high heat resistance. In the 1950s and 1960s, the main focus was on developing high-temperature titanium alloys for aircraft engines and structural titanium alloys for aircraft bodies. A batch of corrosion-resistant titanium alloys were developed in the 1970s, and since the 1980s, corrosion-resistant and high-strength titanium alloys have been further developed. Titanium alloy is mainly used to make compressor components for aircraft engines, followed by structural components for rockets, missiles, and high-speed aircraft.
High temperature alloy refers to a type of metal material based on iron, nickel, and cobalt, which can work for a long time at high temperatures above 600 ℃ and under certain stress conditions; And it has high high-temperature strength, good oxidation and corrosion resistance, good fatigue performance, fracture toughness and other comprehensive properties. High temperature alloys have a single austenitic structure, which exhibits good structural stability and reliability in use at various temperatures. Based on the above performance characteristics and the high degree of alloying of high-temperature alloys, also known as \"superalloys\", it is an important material widely used in aviation, aerospace, petroleum, chemical, and shipbuilding. According to the matrix elements, high-temperature alloys are further divided into iron-based, nickel based, cobalt based and other high-temperature alloys. The operating temperature of iron-based high-temperature alloys can generally only reach 750~780 ℃. For heat-resistant components used at higher temperatures, nickel based and refractory metal based alloys are used. Nickel based high-temperature alloys occupy a particularly important position in the entire high-temperature alloy field, and are widely used to manufacture the hottest end components of aviation jet engines and various industrial gas turbines.
A nickel based corrosion-resistant alloy is an alloy that is based on nickel, contains more than 50% nickel, has certain comprehensive properties such as high temperature strength, and can withstand oxidation or water corrosion. Correspondingly, corrosion-resistant alloys with nickel content greater than 30% and nickel plus iron content greater than 50% are commonly referred to as iron nickel based corrosion-resistant alloys. The Ni Cu alloy (Monel alloy Ni 70 Cu30) produced in the United States in 1905 was the earliest nickel based corrosion-resistant alloy. In 1914, the United States began producing Ni Cr Mo Cu corrosion-resistant alloys (Illium R), and in 1920, Germany began producing Ni Cr Mo corrosion-resistant alloys containing approximately 15% Cr and 7% Mo. In the 1970s, there were nearly 50 types of corrosion-resistant alloy grades produced in various countries. Among them, Ni Cu, Ni Cr, Ni Mo, Ni Cr Mo (W), Ni Cr Mo Cu, Ni Fe Cr, Ni Fe Cr Mo and other alloy series have larger production and wider use, with a total of more than ten grades. China began developing nickel based and iron-nickel based corrosion-resistant alloys in the 1950s, and by the end of the 1970s, there were more than ten different grades.
Inconel is a nickel based alloy containing 14-17% Cr, which has excellent oxidation resistance at high temperatures and is classified as an advanced heat-resistant alloy. Moreover, it has excellent corrosion resistance to various acidic and alkaline environments, and is widely used as a corrosion-resistant alloy. Characteristics of Inconel alloy: 1. Excellent oxidation resistance at high temperatures 2. Excellent carbonization resistance 3. Excellent oxidation resistance in sulfur-containing atmospheres 4. Excellent mechanical properties at both room and high temperatures 5. Excellent stress resistance
Precipitation hardening stainless steel refers to a type of high-strength stainless steel, abbreviated as PH steel, in which different types and quantities of strengthening elements are added to the chemical composition of stainless steel, and different types and quantities of carbides, nitrides, carbonitrides, and intermetallic compounds are precipitated through the precipitation hardening process, which not only improves the strength of the steel but also maintains sufficient toughness. Precipitation hardening stainless steel can be classified into three types based on the metallographic structure of its matrix: martensitic, semi austenitic, and austenitic. Precipitation hardened stainless steel has comprehensive properties such as high strength, high toughness, high corrosion resistance, high oxidation resistance, and excellent formability and weldability.
Ultra high strength steel is a type of alloy steel used to manufacture structural components that withstand high stress. Generally, steel with a yield strength greater than 1180MPa and a tensile strength greater than 1380MPa has sufficient toughness, high specific strength and yield ratio, as well as good weldability and formability. According to the degree of alloying and microstructure, it can be divided into three categories: low alloy, medium alloy, and high alloy ultra-high strength steel. As early as the mid-1940s, due to the development of aviation and aerospace technology, in order to reduce the weight of aircraft and improve flight speed, structural materials were required to have higher specific strength. For this reason, Americans changed the heat treatment process on the basis of AISI4130 and 4340 steel, using quenching and low-temperature tempering to obtain a tempered martensitic structure, which increased the tensile strength of the steel to over 1600MPa. Used for manufacturing aircraft structural components, significant results have been achieved in reducing the weight of aircraft. After the 1950s, new progress was continuously made in improving the strength and toughness of steel, and ultra-high strength steels such as 300M, D6AC, and H-11 were successfully developed. In 1960, International Nickel Corporation of the United States developed martensitic aging steel and gradually formed the 18Ni martensitic aging steel series, with yield strengths of 1400MPa, 1700MPa, 2100MPa, and 2400MPa, respectively, and its fracture toughness reached a high level. After the 1970s, the development of ultra-high strength steel mainly focused on improving toughness. After the 9NiCo series, the United States successfully developed AF1410 secondary hardening ultra-high strength steel based on Hy180 steel. This steel adopts low-carbon martensite and precipitation alloy carbide dispersion strengthening effect, which not only has high strength and toughness, but also has high stress corrosion resistance. It has been used to manufacture important structural components such as aircraft landing gears and tail shafts, and has received attention and favor from the aviation and aerospace sectors. Since the 1990s, in order to meet the needs of the aviation industry, the United States has successfully developed AerMet100 based on AF1410 steel. The steel has a tensile strength of 1965 MPa and a fracture toughness of 120 MN · m, with good stress corrosion resistance. Used for manufacturing aircraft landing gear, it will greatly improve flight safety and reliability, and extend the service life of the aircraft.
Duplex stainless steel (DSS) refers to stainless steel with ferrite and austenite each accounting for about 50%, and generally requiring at least 30% of the lower phase content. In the case of low C content, the Cr content ranges from 18% to 28%, and the Ni content ranges from 3% to 10%. Some steels also contain alloying elements such as Mo, Cu, Nb, Ti, and N. This type of steel combines the characteristics of austenitic and ferritic stainless steel. Compared with ferrite, it has higher plasticity and toughness, no room temperature brittleness, significantly improved intergranular corrosion resistance and welding performance. At the same time, it also maintains the 475 ℃ brittleness and high thermal conductivity of ferritic stainless steel, with superplasticity and other characteristics. Compared with austenitic stainless steel, it has higher strength and significantly improved resistance to intergranular corrosion and chloride stress corrosion. Dual phase stainless steel has excellent resistance to pitting corrosion and is also a nickel saving stainless steel. Since its birth in the United States in the 1940s, duplex stainless steel has developed to the third generation. Its main feature is that the yield strength can reach 400-550MPa, which is twice that of ordinary stainless steel, so it can save materials and reduce equipment manufacturing costs. In terms of corrosion resistance, especially in harsh media environments (such as seawater with high chloride ion content), the resistance of duplex stainless steel to pitting corrosion, crevice corrosion, stress corrosion, and corrosion fatigue is significantly better than ordinary austenitic stainless steel, and can be comparable to high alloy austenitic stainless steel.
Super stainless steel is a special type of stainless steel, which is different from ordinary stainless steel 304 in chemical composition. It refers to a high alloy stainless steel with high nickel, high chromium, and high molybdenum content. Secondly, in terms of high temperature or corrosion resistance, compared with 304, it has better high temperature or corrosion resistance, which is irreplaceable by 304. In addition, from the classification of stainless steel, the metallographic structure of special stainless steel is a stable austenite metallographic structure. In order to meet the demand for comprehensive corrosion resistance in harsh media in modern industrial development, the chromium, nickel, and molybdenum content of stainless steel pipes such as 304 and 316 were increased, and elements such as copper and silicon were added or residual impurities were reduced. Many new high alloy grades were also developed, such as 317LM (00Cr18Ni16Mo5) and 904L stainless steel (00Cr20Ni25Mo4.5Cu) containing about 4.5% Mo, as well as urea grade, nitric acid grade, and nuclear grade Austenitic stainless steel pipes of food grade and other types. According to statistics on the extensive corrosion damage forms of stainless steel pipes from 1962 to 1997, it can be seen that comprehensive corrosion and intergranular corrosion have significantly decreased from 1962 to 1971. However, from 1962 to 1997, local corrosion such as stress corrosion, pitting corrosion, interstitial corrosion, and corrosion fatigue still accounted for a relatively high proportion in corrosion damage. Among them, pitting corrosion and crevice corrosion still account for more than 20%, while stress corrosion and corrosion fatigue still account for more than 10%. Through research, it has been understood that increasing the nickel content in austenitic stainless steel pipes can significantly improve the stress corrosion resistance of steel, and increasing the chromium and molybdenum content can significantly improve the resistance to pitting and crevice corrosion of steel. Stress corrosion and corrosion fatigue usually originate from pitting and crevice corrosion. Therefore, people have begun to pay attention to the development of high alloy austenitic stainless steel with excellent resistance to pitting and crevice corrosion.
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