Abstract
The work is devoted to a study of the microstructure and microhardness of the heat-resistant nickel-based superalloy 58Ni-Cr-Mo-B-Al-Cu after radial-shear rolling. The radial-shear rolling was carried out at a temperature of 925°С in three stages. It was found that the grain size of γ-phase after all rolling stages decreased in the radial direction from the center to the periphery from 62 ± 2 to 2.5 ± 0.2 µm. At the third rolling stage, the grains size was reduced twice in the billet center in a comparison to the initial state. At the same time, individual grains with a size of 100 μm in the billet surface are observed, and grains with a size of 1±0.1 μm are present at the periphery. The microhardness changes in inverse proportion to the grain size, the values increase in the radius direction. The maximum microhardness value is achieved in the peripheral part of the sample and is equal to 5.4 ± 0.6 GPa. According to the EBSD analysis, there is no texture at the billet periphery, but at the middle of the radius there is a two-component axial texture of the <001> + <111> type along the billet axis. The billet center is characterized by the presence of a more pronounced two-component axial texture of the <001> + <111> type along the billet axis. The obtained results indicate the possibility of the gradient structure formation by radial-shear rolling in the heat-resistant nickel-based superalloy 58Ni-Cr-Mo-B-Al-Cu with the initial coarse-grained structure.
Highlights
IntroductionIt is known [1] that superalloys (heat-resistant nickel-based alloys) are used for manufacturing of various parts of gas turbine and rocket engines operating at high temperatures
It is known [1] that superalloys are used for manufacturing of various parts of gas turbine and rocket engines operating at high temperatures
The feature of radial-shear rolling is a complex diagram of the stress-strain state that leads to the appearance of maximum shear deformations in the peripheral surface zone of a rolled billet, which decreases in the central zone direction [10 –13]
Summary
It is known [1] that superalloys (heat-resistant nickel-based alloys) are used for manufacturing of various parts of gas turbine and rocket engines operating at high temperatures These alloys are difficult to deform and are characterized by low technological plasticity. It is useful to form an UFG structure only in the surface layers of a billet keeping the initial coarse-grained one in the billet center Such a microstructural state can be achieved by means of the radial-shear rolling method. The feature of radial-shear rolling is a complex diagram of the stress-strain state that leads to the appearance of maximum shear deformations in the peripheral surface zone of a rolled billet, which decreases in the central zone direction [10 –13] Such processing may result in a gradient structure formation across the rolled billet section. This fact is accompanied by the gradient properties obtaining varying from the surface to rolled billet center
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