Triboengineering properties of austenitic manganese steels and cast irons under the conditions of sliding friction
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TRIBOENGINEERING PROPERTIES OF AUSTENITIC MANGANESE STEELS AND CAST IRONS UNDER THE CONDITIONS OF SLIDING FRICTION O. I. Balyts’kyi,1 V. O. Kolesnikov,2 and P. Kawiak3
UDC 620.1:669.13:669.15:669.74
We analyze the influence of parameters of the graphite phase on the ultimate strength in bending, deflection, and the intensity of fracture of manganese cast irons and steels. The least intensity of wear is exhibited by alloys with graphite inclusions 30–50 μm in length and a hardness of 250 HB. The decrease in the hardness of alloys, improvement of the parameters of the graphite phase, and increase in its amount (occupied area) to 6–10% lead to the disintegration of the metal matrix, decrease its strength characteristics, and promote the intensification of the fracture processes under the conditions of friction. It is shown that, unlike 40, 45, 45G2, and 20KhN hardened steels, the austenitic cold-worked manganese steel is capable of preserving the coating formed by the adsorbed layers of oil and graphite on the surface for 3–4 h under the conditions of shortage of oil.
The parameters of the graphite phase (shape, amount, geometric sizes, etc.) in Fe – C alloys strongly affect all structure-sensitive properties of the materials, including their wear resistance [1, 2]. However, the unambiguous requirements to the microstructure and, in particular, to the parameters of the graphite phase for workpieces operating under the conditions of sliding friction are not formulated. As the most promising alloys used as structural and triboengineering materials, one can mention steels and cast irons with high content of manganese [3]. At the same, the systematic data on the influence of the parameters of the graphite phase on the triboengineering properties of austenitic manganese cast irons and steels are absent and, hence, it is necessity to perform the corresponding complex investigations. Materials and Experimental Procedure The aim of the present work is to study the influence of the parameters of the graphite phase of austenitic manganese cast irons on their mechanical and triboengineering characteristics. The basic chemical composition of the analyzed cast irons is as follows (wt.%): 3.7 C, 12.0 Mn, 3.0 Si, 1.0 Ni, 2.5 Cu, and 0.4 Al. The concentrations of Cr, V, and Ti and some properties of the alloys are presented in Table 1 [4]. The wear resistance was measured in an SMTs-2 friction machine according the roller-shoe scheme under the conditions of boundary and dry friction. As the counterbody, we used a roller made of 45G2 hardened steel with a hardness of 55 HRC. The sliding velocity was equal to 0.628 m / sec. The shoes were cut out from specimens cast in sand–loam molds ( ∅ 30 mm). The microstructure was studied in MIM-8M and PMT-3 microscopes with computer processing of the images aimed at the quantitative analysis of the structure and with the help of a JSM-6100 scanning microscope. 1 Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, Lviv. 2 Dal’ East-Ukrainian National University, Lugansk. 3 Inst
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