For effective operation under extremely high temperature conditions, properties such as heat resistance (creep strength) and scale resistance are of critical importance for precision alloys and steels. This is especially important for installation components subject to significant mechanical loads. These include aircraft engines, gas turbines, thermal power plants, industrial heating furnaces, as well as equipment at oil refining and petrochemical enterprises.
Scale resistance (oxidation resistance) is determined by the ability of metals to resist chemical corrosion under elevated temperature conditions in a dry gas environment. This is linked to formation on metal surfaces of oxide films that act as a protective barrier. For example, iron (Fe) with oxygen (O2) at temperatures up to 560–600°C forms densely bound scale-resistant oxide films Fe2O3 and Fe3O4, which hinder diffusion of metal atoms (cations) and oxygen (anions). However at higher temperatures (above 600°C) these films break down, and a layer of loose FeO oxide forms on the metal surface, which promotes intensive oxidation of steels and iron-based alloys.
One of the key factors affecting scale resistance of materials is their chemical composition, since exactly it determines protective properties of oxide films. Table 1 compares scale resistance of several chemical elements — pure metals.
Table 1 - Scale resistance of metals in air at working temperatures
Heat resistance of a material is determined by its ability to retain its strength at high temperatures. Main heat resistance indicators include long-term strength limit and creep limit, which must match service conditions of finished products or structures.
Choice of heat resistance criterion for precision alloys and steels depends on the planned service life of the machine or mechanism manufactured from the given material. Table 2 shows recommended service lives of heat-resistant structures depending on their purpose.
Table 2 - Service life of heat-resistant structures
The history of superalloys began in 1929 when scientists Bedford and Pilling made changes to a chromium-nickel alloy. By adding titanium (Ti) and aluminum (Al) to it they were able to significantly increase the material’s creep resistance. Interestingly, superalloys were discovered shortly before development of jet engines. The first prototypes of aircraft with turbine engines created in England and Germany in the 1930s required new materials able to withstand extreme operating conditions: high temperatures and elevated loads.
For a long time superalloys were produced only for the military industry as the main material for creating jet engines. But in the mid-last century such materials also became in demand in other industries, in particular for manufacturing various drive devices (gas pipeline pumps, gas turbines for power plants). From the 1950s to the 1960s intensive development of heat-resistant superalloys began worldwide, leading to improvement of technologies and increase in production volumes. Over time these materials became an integral part of the aviation and energy industries, ensuring reliability and durability under the most extreme service conditions.
One of the key requirements imposed on superalloys is minimal content of harmful impurities such as sulfur (S), phosphorus (P), lead (Pb), bismuth (Bi), and tellurium (Te). And the main goal of researchers and engineers in this field is raising reliability and economic efficiency by reducing use of expensive alloying elements at temperatures up to 680°C. Among promising development directions one should highlight application of nickel (Ni) based materials.
One of the product types of Petersburg Plant of Precision Alloys is corrosion-resistant steels of grades 12Kh18N9, 12Kh18N10T, 12Kh18N9SMR (EP-414). They undergo strict quality control at every production stage, which makes it possible to guarantee their conformity to the highest standards.
For purchasing cold-rolled strip from corrosion-resistant steels as well as precision alloys, call the listed phone or leave requests on the website.
At the enterprise mastering of production of scale-resistant and heat-resistant chromium-nickel (KhN53BMTYU, analogue of foreign alloy NN 718) and molybdenum-chromium-nickel alloys is actively underway, facilitated by the work of the research center.
You can learn about cooperation terms and technical capabilities of the PZPS research center by calling +7 812 740-76-87 or writing to nic@pzps.tech. Our specialists will contact you shortly and answer all questions in detail.
