At the end of the 19th century, research found that when the nickel content in a nickel-iron alloy was about 36%, the linear expansion coefficient of the alloy was very low. Based on this property, a series of alloys with low linear expansion coefficients have been developed. Among them, Invar alloy is the most famous one and plays an irreplaceable role in some specific applications.
However, Invar alloys have significant limitations in their applications. Its low expansion properties are only present in the temperature range below 200°C. When the temperature rises above 200°C, the material reaches the Curie temperature and the magnetic properties of the alloy transform, thus losing the low expansion properties.
In order to solve the above problems, people added cobalt to nickel-iron alloy. The addition of cobalt increases the Curie temperature of the alloy, thereby reducing the high-temperature linear expansion coefficient of the alloy. This nickel-iron-cobalt alloy is called Kovar alloy and has low expansion properties in the range of 20 to 450°C.
In the 1970s, international oil prices rose sharply, and people began to develop more efficient engines. The spacing between engine parts has a great impact on the engine’s operating efficiency. If the parts are made of low-expansion alloys, the spacing between parts can be controlled.
Although Kovar alloy can achieve low expansion properties at high temperatures, the strength of the alloy is not high. In engines, components are subjected to cyclic stresses at high temperatures for long periods of time. Kovar alloy is obviously not up to the task. Therefore, improving the strength of low-expansion alloys has become key.
Precipitation strengthening is an effective method to increase the strength of alloys. Therefore, attempts have been made to add aluminum, titanium, niobium and tantalum to nickel-iron-cobalt alloys. After aging treatment, the alloy reaches a precipitation-strengthened state. This greatly improves the strength of low-expansion alloys at high temperatures. Incoloy 903 was developed against this background. It is called the first generation low expansion superalloy. The high-temperature strength of Incoloy 903 can reach the level of Inconel 718, while the linear expansion coefficient is only half that of Inconel 718.
Incoloy 903 has excellent high temperature strength and low linear expansion coefficient. However, because it does not contain chromium, Incoloy 903 has poor antioxidant properties. Oxidation reactions reduce the material’s durability and increase notch sensitivity. In order to avoid this problem, Incoloy 903 must use special processing techniques to reduce the chance of oxidation diffusion. However, it still cannot completely solve the problem of durability performance under long-term high-temperature use.
Alloy researchers continue to look for solutions to this problem. At the same time, they successively developed Incoloy 904, Incoloy 905 and Incoloy 906 alloys. Finally, Incoloy 907 came into being. It solves the durability performance issues of Incoloy 903.
Research has found that aluminum content has a negative impact on the durability properties of Incoloy 903 alloy. Therefore, the aluminum content of Incoloy 907 alloy is strictly controlled (less than 0.2%). Aluminum also plays a role in precipitation strengthening. To balance the reduction in aluminum content, Incoloy 907 is strengthened by adding more niobium instead of aluminum. Incoloy 907 is also known as the second generation low expansion superalloy.
By optimizing its chemical composition, Incoloy 907 no longer requires special processing like Incoloy 903. However, to ensure durable properties, it requires a longer aging treatment than ordinary precipitation-strengthened alloys. This overaging treatment reduces the transient properties of the alloy.
Not long after the introduction of Incoloy 907 alloy, researchers accidentally discovered that increasing the silicon content could further improve the durability properties of the low-expansion alloy. This becomes the key to solving the problem. Researchers took advantage of this property to add more silicon content to Incoloy 907 and better control the aluminum content, developing a third-generation low-expansion superalloy: Incoloy 909.
Incoloy 909 controls the silicon content to approximately 0.4% and the aluminum content to less than 0.15%. This maximizes the durability performance of Incoloy 909. At the same time, by controlling the grain size, Incoloy 909 achieves better overall performance.
Tianjin Anton Metal Manufacture Co., Ltd. is a company specializing in the production of various nickel-based alloys, Hastelloy alloys and high-temperature alloy materials. The company was established in 1989 with a registered capital of 10.0 million, specializing in the production and sales of alloy materials. Anton Metal’s products are widely used in aerospace, chemical industry, electric power, automobile, nuclear energy and other fields, and can also provide customized alloy material solutions according to customer needs. If you need to know the price consultation of alloy materials or provide customized alloy material solutions, please feel free to contact the sales staff.
==========================================
www.antonmetal.com
ANTON METAL｜ Your specialty alloys manufacturer
Email: dominic@antonmetal.com
Phone: +8613132148618(wechat/whatsapp)
Post time: Nov-18-2023
