Zones of contact interaction in steel matrix near inclusions under the laser action
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ZONES OF CONTACT INTERACTION IN STEEL MATRIX NEAR INCLUSIONS UNDER THE LASER ACTION S. I. Gubenko
UDC 621.785:535.211:669.15-194:669.017
Specific features of the process of saturation of steel matrix with elements of nonmetallic inclusions are investigated for different modes of the laser action. The role of this process in the formation of the local structure of the matrix near nonmetallic inclusions in low- and medium-carbon steels is demonstrated. Keywords: steel, nonmetallic inclusion, laser treatment.
It is shown that the process of laser treatment of steels is accompanied by the fusion of refractory nonmetallic inclusions, melting of fusible inclusions, and enrichment of the surrounding matrix with elements from the chemical compositions of the inclusions [1–4]. However, these phenomena require subsequent investigations. The aim of the present work is to study the specific features of the zone of saturation of the steel matrix with elements of the inclusions for different modes of the laser action. Materials and Procedures Specimens of 60G, 08kp, 08, 08Yu, NB-57 (rail), and É3 (electrical) steels with preliminarily polished surfaces were subjected to laser irradiation in a GOS-30M installation. The pulse energy was equal to 10, 18, 25, and 30 J, the heating rate to 10 5 °/sec, the time of action of the pulse to 1.010 3 , 2.510 3 , 3.610 3 ,
4.210 3 , and 6.0 10 3 sec, and the cooling rate to 10 6 °/sec. The inclusions were identified metallographically, by the micro-X-ray spectral analysis, and by the petrographic method [1]. Results of Investigations and Discussion Under the laser action, we observe rapid exchange of atoms between the inclusions and the steel matrix characterized by the abnormally high mobility of the atoms, which does not agree with the conditions of classical diffusion (abnormal mass transfer). The driving force of this exchange is the difference between the chemical potentials of the elements contained in the inclusion and in the matrix. The values of the diffusion coefficients of atoms near the melting points of steels subjected to laser irradiation are higher than the equilibrium values by an order of magnitude and even more [1]. We also mention the possibility of ionization of atoms of the components of steels and inclusions under the laser action, which also affects the rate of mass transfer. The mass transfer caused by the laser action is favored by the motion of defects of the crystal structure formed by the thermal impact, by the processes of melting and convective mass transfer, by the electron and electromagnetic National Metallurgical Academy of Ukraine, Dnepropetrovsk, Ukraine; e-mail: [email protected]. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 46, No. 4, pp. 21–26, July–August, 2010. Original article submitted February 16, 2010. 448
1068-820X/11/4604–0448
© 2011
Springer Science+Business Media, Inc.
ZONES OF CONTACT INTERACTION IN STEEL MATRIX NEAR INCLUSIONS UNDER THE LASER ACTION
449
interaction of inclusions with the matrix, and
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