Dependence of the Corrosion Behavior of Austenitic Chromium-Nickel Steels on the Paramagnetic State of Austenite
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DEPENDENCE OF THE CORROSION BEHAVIOR OF AUSTENITIC CHROMIUM-NICKEL STEELS ON THE PARAMAGNETIC STATE OF AUSTENITE G. V. Snizhnoi
UDC 669.15:537.621.4:620.193.4
It is experimentally established that the corrosion resistance of chromium-nickel austenitic steels depends on the paramagnetic state of austenite. Thus, the corrosion resistance increases (and the corrosion rate K decreases) as the specific magnetic susceptibility of austenite χ 0 increases, and vice versa.
The presence of low contents Pα of δ -ferrite (0.005–0.5%) indirectly affects the corrosion process ( Pα depends on χ 0 and a good correlation between K and χ 0 was experimentally established). The corrosion resistance increases with Pα . It is proposed to use the parameters χ 0 and Pα for the prediction of the corrosion intensity.
Keywords: austenite, δ -ferrite, corrosion, magnetic susceptibility.
Despite numerous studies of the processes of corrosion of various materials [1–6], the problems encountered in practice require the comprehensive investigation of the mechanisms of corrosion behavior aimed at guaranteeing the reliable and safe operation of contemporary structural materials used in the construction of various types of pipelines. It is worth noting that the distribution of δ -ferrite is nonuniform even in steels of the same grade and depends on the coordinate. Thus, the concentration of δ -ferrite in 08Kh18N10T steel varies across the width of the sheet in the direction normal to the direction of rolling from 0.01–0.4% [6]. Chromium-nickel austenitic steels contain small amounts of δ -ferrite and characterized by different local interactions with corrosive media. In fact, the low content of δ -ferrite cannot significantly affect the corrosion behavior of steels of the austenitic class [6]. It is possible to assume that the corrosion is affected by the preliminarily formed atomic-magnetic state of the austenitic matrix determined by the sum of magnetic moments of atoms contained in the unit mass (specific magnetization) and described by the external parameter, namely, by the specific magnetic susceptibility χ 0 of austenite.
The aim of the present work is to study the dependence of the corrosion resistance (GOST 9.908-85) of AISI-304, 08Kh18N10 and AISI 321, 08Kh18N10T austenitic chromium-nickel steels on the paramagnetic state of the austenitic matrix (parameter χ 0 ) and to estimate the influence of the low content of δ -ferrite on the corrosion behavior of these steels.
Experimental Studies and Their Discussion For the investigations, we used two groups of materials: AISI 304, 08Kh18N10 and AISI 321, 08Kh18N10T whose chemical compositions are presented in Table 1. “Zaporizhzhya National Technical University,” Zaporizhzhya, Ukraine; e-mail: [email protected]. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 49, No. 3, pp. 58–62, May–June, 2013. Original article submitted September 26, 2012. 1068-820X/13/4903–0341
© 2013
Springer Science+Business Media New York
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G. V. SNIZHNOI
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Table 1. Chemical Compositions of the An
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