1168 Russian Physics Journal, Vol. 51, No. 11, 2008 GRADIENT STRUCTURE-PHASE STATES FORMED IN HADFIELD STEEL DURING DRY SLIDING WEAR E. A. Aleshina, Yu. F. Ivanov, A. V. Kolubaev, UDC 669.15:620.179 S. V. Konovalov, and V. E. Gromov SEM and TEM analyses have been used to study the state of the surface layer and the evolution of the defect substructure of Hadfield specimens as a function of depth below the worn surface. Gradient structure is shown to form in the examined steel type during dry sliding wear. The defect density in the structure and its microhardness are found to reduce with depth below the worn surface. Keywords: dry sliding wear, Hadfield steel, tribology, worn surface. INTRODUCTION Hadfield steel is characterized by high wear resistance. This is due to the fact that the material lends itself to extremely intensive work hardening under plastic deformation in the sliding-contact zone. A search for new ways of improving the wear resistance of commercial materials, including austenitic steels, assumes a detailed analysis of structure-phase transformations that take place both in the surface layer of the material, and below the worn surface. The aim of the present work is to perform layer-by-layer SEM and TEM analyses of Hadfield steel specimens to find an explanation for changes in the defect substructure of the material during dry sliding wear. 1. TEST MATERIAL AND INVESTIGATION TECHNIQUE The test material was Hadfield steel (Fe–1.1 wt.% C–13 wt.% Mn) in the polycrystalline state. Mechanical tests were performed with the use of a universal frictional testing machine (2168 UMT-1) operated in the dry sliding-wear regime. The tests employed a face-seal mating scheme. The specimens were thrust plain bearing bushings made from the Hadfield steel type under study. The bushings were 31.1 and 39 mm in inner and outer diameters, respectively, and 10 mm in height. The counterbody was a disk made from hardened Fe–1 wt.% C steel (62 HRC). A bushing end face was held against the disk counterface. The load pressure, sliding rate, and test time were 2 and 4 MPa, 10 min –1 , and 5 hrs, respectively. The worn-surface pattern and the defect substructure and phase composition of the subsurface layer of the Hadfield steel specimens were examined using SEM and TEM analyses. Thin foils for the microscopic examination were prepared by electrolytic thinning of specimen plates on the side opposite to the worn surface. 2. RESULTS AND DISCUSSION The mechanical tests of the Hadfield steel specimens have been conducted at room temperature under dry sliding wear conditions. The outcome of the trials was a marked increase in the microhardness of the worn surface (Fig. 1). As the depth below the worn surface increased, the microhardness decreased approaching the values Siberian State Industrial University, Novokuznetsk, Russia, e-mail: gromov@physics.sibsiu.ru. Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 11, pp. 48–53, November 2008. Original article submitted October 3, 2006; revision submitted March 15, 2008. 1064-8887/08/5111-1168 ©2008 Springer Science+Business Media, Inc.