• MATERIALS

    On the role of non-metallic inclusions in ensuring crack resistance of steel

    Machines. Technologies. Materials., Vol. 17 (2023), Issue 5, pg(s) 198-201

    The influence of non-metallic inclusions on the formation of defects in deformed steels and their role in providing crack resistance are considered. It is shown that non-metallic inclusions as stress and strain concentrators are one of the most dangerous sources of defect initiation in steels during pressure treatment. It has been established that the nature of cracks and the features of their growth near nonmetallic inclusions are determined by the type of inclusions, as well as by the scheme of the local stress state, which depends on the loading conditions. An analysis was made of the features of the initiation and development of the cracks near non-metallic inclusions of various types during tensile strain, compressive and bending deformation. It is shown that the most severe way of deformation for the inclusion-matrix system is tensile strain, the softest is compression.

  • MATERIALS

    About corrosion damage of the railway wheels

    Machines. Technologies. Materials., Vol. 16 (2022), Issue 7, pg(s) 243-247

    Corrosion mechanism and rate of different chemical composition and structural condition of wheel steel were investigated. It was shown that “white layers”, variation in grain size and banding of wheel steel structure results in corrosion rate. Microstructure of steel from different elements of railway wheels after operation with corrosion was investigated. Wheel steel with addition of vanadium corroded more quickly than steel without vanadium. Non-metallic inclusions are the centres of corrosion nucleation and their influence on corrosion depends on type of inclusion. Mechanism of corrosion of wheel steel corrosion was discussed.

  • The features of recrystallization of steels under laser action

    Materials Science. Non-Equilibrium Phase Transformations., Vol. 8 (2022), Issue 1, pg(s) 7-9

    The features of recrystallization of steels with different chemical composition and type of crystal lattice under laser action were investigated. These processes are of great importance in high-speed laser heating and cooling, as well as in the formation of the microstructure of steels under the influence of residual heat.
    It was found that recrystallization under laser action has signs of a dynamic process due to an increase in the dislocation density. In addition, the dislocation substructure of steel is inherited from the initial hot-deformed state. It is shown that the mechanism of laser recrystallization depends on the type of steel, chemical composition, and crystal lattice.
    In different steels, the development of primary, collective, and secondary recrystallization was observed. In this case, the change in the grain structure of steels took place against the background of an increased density of dislocations and the formation of a cellular dislocation substructure.

  • TECHNOLOGIES

    About the possibility of local laser hardening of the treed of railway wheels

    Machines. Technologies. Materials., Vol. 15 (2021), Issue 5, pg(s) 181-184

    The features of structural changes in the cove zone on the tread of worn out railway wheels were investigated. The influence of laser processing in pulsed and continuous mode on the nature of the structure and properties of wheel steel was shown. The influence of laser treatment on the increase in the hardness and wear resistance of wheel steel has been established. It was shown possibility and necessity of local laser hardening of cove zone of railway wheels tread by coming out of bainite structure. A method for improving the wear resistance of the tread by local laser treatment has been proposed.

  • Phase transformations in non-metallic inclusions under laser action

    Materials Science. Non-Equilibrium Phase Transformations., Vol. 7 (2021), Issue 1, pg(s) 6-10

    It was found that in the process of pulsed laser action, various phase and structural transformations occur in non -metallic inclusions, which take place under nonequilibrium conditions. It is shown that the melting of inclusions under laser action is corresponded with change of their structure and phase composition. Also it is shown that the nature of these transformations depends on the type of nonmetallic inclusion. It was found that nonequilibrium phase transformations contribute to a change in the structure, phase composition, properties and sizes of nonmetallic inclusions, as well as the inclusion-matrix interphase boundaries of steel. It is shown that changes in the structure and properties of non-metallic inclusions affect their behavior and the formation of defects in the laser-strengthened layer of steel
    products.

  • Transformation of heterophase inclusions “dispersed phases are in non-metallic matrix” in steels under laser action

    Materials Science. Non-Equilibrium Phase Transformations., Vol. 6 (2020), Issue 2, pg(s) 30-33

    Melting and crystallization of heterophase non-metallic inclusions “dispersed phases are in non-metallic matrix” was investigated. Mechanism of melting of the inclusions “dispersed phases are in non-metallic matrix” and inclusion-matrix boundaries under contact laser melting with steel matrix in the conditions of abnormal mass transfer connecting with formation of zones with high dislocation density and also with electron and electro-magnetic interaction between inclusion and steel matrix was proposed. That allows to create the possibilities for the influence on the inclusion-matrix boundaries and also on the chemical and phase composition of surface layer of non-metallic inclusions “dispersed phases are in non-metallic matrix”. Peculiarities of structure of non-metallic inclusions after speed crystallization were investigated. It was shown that under laser action the initial structure of inclusion-steel matrix boundaries transits into unstable equilibrium high-energy condition that cause development of the dissipation processes connecting with aspiration of system inclusionmatrix to the state with minimum of the free energy. In the result of the system inclusion-matrix transits to the state of unstable equilibrium which determines structure and properties of laser-quenched interphase boundary. Processes of melting, fusion and dissolution of nonmetallic inclusions “dispersed phases are in non-metallic matrix” and also of the melting of steel matrix play the great role in transformation of interphase inclusion-matrix boundaries under laser action.

  • MATERIALS

    Steels with bainite structure for railway wheels

    Machines. Technologies. Materials., Vol. 14 (2020), Issue 5, pg(s) 215-218

    Some wheel steels inclined for the self-quenching on bainite structure were produced and investigated after hot deformation and heat strengthening. Steels contained 0,12…0,45% of carbon, and also Si, Mn, Mo, Cr, Ni, V, Ti, Al. Steels with bainite structure after hot deformation and tempering were investigated. It was shown the possibility of the railway wheels production with bainite structure and hardness of 400HB without heat strengthening treatment. The results of investigation shown the possibility of railway wheels production with bainite structure, hardness of 400 HB and high complex of the mechanical and operating properties without heat strengthening treatment. These tasks solved owning to application of new wheel steels and up-to-date technology.