Structural phase states and properties of rails after long-term operation

Physical Nature of Strengthening Mechanisms During Extremely Long-Term Operation of Rails

“…The complex quantitative studies of structure, phase composition, defect substructure, and tribological properties at a different distance from the tread surface along the central axis and along the fillet have been carried out in our works [15][16][17][18][19].…”

“…Measurements of hardness done along the head crosssection in the transverse direction demonstrate that the HRC hardness at a depth of 2 mm is 37.1, at a depth of 10 mm -35.8, at 22 mm -35.6. Microhardness at a depth of 2 mm amounts to 1481 MPa; microhardness at a depth of 10 mm is substantially lower and amounts to 1210 MPa [15][16][17].…”

Formation of Gradient Structure in Rails at Long-Term Operation

“…The depth of deformation from tread surface is insignificant and is less than 35 μm ( Figure 2b). It is established that microhardness at the depth 2 mm amounts to 1481 MPa at depth of 10 mm it is substantially lower and amounts to 1210 MPa 10 .…”

“…• formed as a result of surface saturation with different elements of penetration (cementation, nitriding, boriding, etc) or elements of substitution (gilding, silver plating, chromium plating, nickel plating, etc); • emerged as a result of surface cold hardening or other methods of surface mechanical hardening; • formed as a result of ultrasonic machining of surface; • meeting the requirements of different types of single-and multi-layer coatings; • appeared after of shock waves, electron beams, powerful ion beams, intensive plasma flows; • emerged in consequence of laser or microwave radiation, as well as in plasma of gas discharge; It is apparent that at severe deformation effect being realized at long operation the different processes (recrystallization, relaxation processes, phase transitions, decomposition and formation of phases, amorphization, etc) leading to the evolution of structural phase states and being accompanied by the formation of structural phase gradients [5][6][7][8][9][10][11][12][13] may take place.…”

“…A behavior of rail steel at long operation, in its nature, is very close to that of metallic materials at severe (megaplastic, MPD) deformation [5][6][7][8][9][10] . The general mechanisms of structural formation and evolution at megaplastic deformation of perlite steel are the following: formation of nanometer grains of ferrite, deformation-induced decay of cementite plates and subsequent formation of nanodimensional cementite on dislocations and boundaries of ferrite nanograins.…”