STUDY OF THE STRUCTURE, PHASE COMPOSITION, PHYSICOMECHANICAL PROPERTIES, AND ALSO OPTIMIZATION OF HEAT TREATMENT PROCESSES OF CAST HEAT-RESISTANT NICKEL ALLOY ЕР202 BY THE METHOD OF MATHEMATICAL MODELING
General information about the EP202 heat-resistant weldable alloy with a nickel-chromium matrix is given. Its chemical composition, manufacturing technology, recommended heat treatment modes for short-term and long-term parts, as well as recommended maintenance modes for castings and rodsheets are presented. A description of the structure and phase composition of the alloy in the cast state and after heat treatment is given. The mechanical properties of the alloy depending on the test temperature and heat treatment conditions for longitudinal and transverse specimens are given. The physical properties of the alloy at various temperatures are also described. Further, the study presents the study of the modes of stepwise aging on the structure and mechanical properties of the EP202 alloy. An increase in mechanical properties after two-stage aging in comparison with the initial heat treatment due to a more uniform distribution of the strengthening γ¢-phase over the volume of the alloy was established. With the help of the obtained regression equations, the optimal temperature of the first stage of two-stage aging (540 C) was established, which ensures an increase in the level of impact strength by (20...25) %.