Forming modified layers on the surface of steel during ultrasonic finishing

Zh G. Kovalevskaya, V. A. Klimenov, Yu F. Ivanov, P. V. Uvarkin

Research output: Contribution to conferencePaperpeer-review

Abstract

The authors investigated the way ultrasonic finishing influences structure and properties of the surface layers of ferrite and pearlite grades of carbon steels. Ultrasonic modification was assessed according to the results of metallographic, electron microscopic analysis of samples. The surface and near - surface structure changes were accomplished by means of splitting up the microstructure into fragments and blocks with the formation of microdistortion of crystal lattice. During the ultrasonic treatment, all steels revealed the maximum level of microhardness on their surface which was steadily decreased in depth. Based on a number of carbon proeutectoid steels, we have studied the effect of ultrasonic surface treatment on the microstructure and microhardness of the obtained modified layer. The surface treatment of specimens was carried out by an ultrasonic device that allows alternating compressive and shear deformation. The deformation was induced by the action of the moving indentor normally oscillating with ultrasonic frequency [1-3]. Optical metallographic analysis and microhardness measurements were performed with the use of transverse metallographic sections cut out of the obtained specimens. Diffraction electron microscopy was used to examine a thin surface layer of the specimens. Specimens of steels 20, 45 and 60 (in the Russian designation) in the annealed state have a ferrite-pearlite structure. The ratio of the ferrite and pearlite constituents is known to vary depending on the carbon content in the alloy. In steel 20 the ferrite constituent dominates, while in steel 60 - pearlite one. Optical and scanning electron microscopy is applied to examine the structure of the main structural constituents of these steels. In the initial state steel 20 consists of ferrite grains 10…25 µm in size and pearlite grains of 3…5 µm in size. Pearlite grains are located at junctions of ferrite grain boundaries and occupy 20…25 vol. %. Ferrite has a polycrystalline structure. Within grains there is the structure of dislocation chaos with the scalar dislocation density ρ ~ 3×109 cm-2 (Fig. 1a).

Original languageEnglish
Publication statusPublished - 2007
Event16th International Metallurgical and Materials Conference, METAL 2007 - Hradec nad Moravici, Czech Republic
Duration: 22 May 200724 May 2007

Conference

Conference16th International Metallurgical and Materials Conference, METAL 2007
CountryCzech Republic
CityHradec nad Moravici
Period22.5.0724.5.07

ASJC Scopus subject areas

  • Mechanics of Materials
  • Metals and Alloys
  • Condensed Matter Physics

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