13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Surface layer modification of 12Cr1MoVand 30CrMnSiNi2 steels by Zr+ ion beam to improve the fatigue durability Ilya Vlasov1,2,*, Sergey Panin1,2, Viktor Sergeev2, Alfred Sungatulin2, Mark Kalashnikov2, Boris Ovechkin1, Viktor Panin1,2 1Department of Material Science in Mechanical Engineering, Institute of High Technology Physics Tomsk Polytechnic University, 634050, Tomsk, Russia 2 Laboratory of Polymer Composite Materials, Institute of Strength Physics and Materials Sciences SB RAS, 634021, Tomsk, Russia * Corresponding author: good0@yandex.ru Abstract A cyclic tension and alternating bending tests of 12Cr1MoV and 30CrMnSiNi2 steels specimens in as–supplied state and after surface nanostructuring by Zr+ ion beam have been carried out. Distinctions in formation of strain induced relief, as well as the cracking pattern of modified surface layer are illustrated by methods of optical microscopy and interferential profilometry. Changes to occur in subsurface layer are characterized by means of nanoindentation and fractography (scanning electron microscopy) of fracture surfaces. The description of differences of deformation behavior is carried out with use of the multiple cracking concepts. Keywords strength, nanostructuring, multiple cracking, deformation, fracture. 1. Introduction The majority of products and machine parts during their exploitation experience the impact of variable loads, which can give rise to their fatigue fracture. In doing so regardless the long history of study the problem of fatigue fracture and approaches to increase fatigue durability are of substantial importance [1]. Surface modification is an effective way both to protect and to improve the mechanical properties of structural materials. On the other hand, under mechanical loading the distinction of elastic modules of a modified surface layer and adjacent bulk material causes the stress concentrators to occur, whose relaxation may give rise to localized development of plastic deformation or fracture [2]. Under cyclic loading such distinction of the properties brings to microcracking within strengthened surface layer, to act as structural micronotches. Therefore, the choice of modes and options for modifying the surface layer should be a compromise between strength/ductility of this layer and its thickness (this as well depends on several other factors, including adhesion etc.). Ion implantation technique for a long time is widely used for industrial applications and is an extensively studied process. Recently, with the use of vacuum arc ion sources the modes of surface layer nanostructuring which allowed modifying surface layers with a thickness of some microns that is several times higher in contrast with ion implantation at conventionally used regimes were realized. Such nanostructured surface layers are not coatings yet, but no longer can be called ion-implanted ones [3]. Study of influence of such layers on fatigue life-time of structural steel specimens is of particular interest due to the possibility of simultaneously improvethe fatigue durability and wear resistance. To study the influence of surface layer nanostructuring of 12Cr1MoV and 30CrMnSiNi2 steels by Zr+ ions on the fatigue durability increase is the purpose of this work.
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