Manufacture of disc forgings from heat-resistant nickel and titanium alloys
Manufacture of disc forgings from heat - resistant nickel and titanium alloys. A complex of fundamentally new technologies implemented on the newly developed specialized unique equipment for melting and processing by pressure was developed to solve the most important task of the national economy to provide manufacturing small-sized gas turbine engines with cost-effective, high quality billets of discs from heat-resistant nickel and titanium alloys with effective technical-and-economical indexes. This equipment has no analogues in domestic and foreign industry.
The developed technological process proposes to use both serial press-bar and, for the first time in the world practice, a cut-to-length billet produced by high-gradient directional solidification (HGDS) method as a primary blank for isothermal forging under superplasticity conditions.
For realization of this process the institute developed a special technology of heat-resistant alloys manufacture including a deep decarbonization and refining of melt, usage of charge materials of high purity in terms of additions, complex refining with rare earth metals, usage of all kinds of wastes of metallurgical and casting productions of heat -resistant alloys.
The developed technology provides ultrahigh purity of heat-resistant alloy in terms of additions, achievement of narrow alloying range, saving of expensive and deficit materials.
High gradient technology of directional solidification, which has no analogues in worldwide practice has been created. For the first time in the domestic and international practice a specialized vacuum casting-melting complexes UVNK-14 and UVNK-10 with computer control systems for high-gradient directectional solidification of billets from heterogeneous alloys for the following deformation have been designed and manufactured in the production center of VIAM. An integrated computer control system of billets casting technological processes was developed at VIAM For realization of this technology.
Principally new methods of thermomechanical treatment of difficult-to-deform heterogeneous alloys, which provide formation of regulated structures distinguished with higher ductility and superplasticity under optimal temperature- rate parameters of deformation have been developed at FSUE «VIAM».
As a result, a unique processing technology of plastic working – isothermal forging of hard-to-form nickel alloys in air was developed, which provides manufacturing of intricately shaped disc billets with guaranteed properties level.
The process of controlled dynamic recrystallization is used as a basic mechanism for achievement of metal ductility and homogeneity of its structure.
In comparison with foreign technologies, a distinctive feature of this new complex energy- and resource-saving technology is conduction of high- temperature isothermal forging in air but not in vacuum units of elaborate design and equipped with molybdenum dies.
As opposite to forging in vacuum used abroad, long-life heat-resistant alloy for dies and special protective antioxidant coatings, which serve simultaneously as high-temperature lubricant in the course of deformation were developed and applied for the first time in home practice.
Special protective technological high-temperature enamel coatings to protect parts made from heat-resistant Ni and Ti alloys were developed. Protective technological coatings developed in VIAM allow to carry out non-oxidation technological heating of steels in common furnaces instead of furnaces with controlled atmosphere. Using of protective coatings in technological processes provides to produce close tolerance forgings, to save metal up to 30% and electric power consumption - up to 50%. Coatings increase the die tooling durability 2-3 times.
A pilot production of forged disks for gas turbine engines (GTE) and power units was launched at VIAM for practical realization of the developed technologies. Technological equipment was modified to embody billet heating and deformation processes in automatic mode using the developed software with exact keeping optimum thermomechanical parameters of deformation. Forgings are manufactured by 630 and 1600 tnf isothermal presses with induction heating of dies.
A composition of long-life forging heat-resistant alloy was developed for isothermal forging at temperature up to 1200 °С in the air, protective-technological coatings serving simultaneously as effective technological lubricants during the forging process were worked out as well. The developed technologies and the complex of equipment created to realize the developed technologies are unique for the domestic industry and abroad. The technology of high-temperature isothermal forging in the air compares favorably with the world level.
At the present time the serial supply of cost-effective high-quality forgings of super heat-resistant nickel and high-strength titanium alloys on the created units is made by orders of the following enterprises: JSC "Motor Sich", JSC "Kaluga Aviation Engines" (Kadvi), OJSC “Omsk Engine Design Bureau” to use in AI450, MS-500, SAS-75 and other articles.
- production of cost-effective close tolerance forgings of super heat-resistant difficult-to-deform alloys by superplastic deformation under optimum thermomechanical parameters;
- 2-3 times increase of MUF due to reduction of processing allowances in the course of forging and machining;
- 3-5 reduction of labor input and power consumption due to a decrease of operations number during forging and machining of parts;
- 4-5 times increase in output;
- An increase of uniformity of macro- and microstructure and reduction of dispersion of mechanical properties - 1.5-2 times;
- Reduction of costs of forgings by 30-50%.