PSI - Issue 36

Pavlo Prysyazhnyuk et al. / Procedia Structural Integrity 36 (2022) 130–136 Pavlo Prysyazhnyuk et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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1. Introduction High-manganese steel, so-called Hadfield steel, is widely used material for the applications where high impact wear resistance is needed, for instance, it is used for wear parts of cone crushers, mining equipment, excavator bucket teeth, etc. The surface hardness of such parts can be significantly increased from ~200 to ~500 HB by work hardening during exploitation under conditions, where dominant loads are dynamic. Most researchers explain such properties changes in terms of stacking fault energy (SFE) of austenite phase dependence on Mn to C ratios. So, in steels similar to Hadfield steel the relationships between С and Mn tends to decreasing of SFE values and, as a result, most energetically favorable mechanism of its hardening is the deformation twining without phase transformations. Despite high work-hardening rate of the high-manganese steels, its abrasion resistance remains rather low, especially in cases where mode of abrasive particles acting changes from direct penetration to microcutting (Ropyak et al. (2019), Pashechko and Montusiewicz (2012)); and if the wear process is complicated by presence of chemical aggressive environments it tends to catastrophic wear rates (Saakiyan et al. (1987), Pashechko et al. (2003)). Moreover, as was shown in Bayhan (2006), wear resistance of high-manganese (14 wt. % Mn) steel, investigated in three-body abrasive wear conditions is almost equivalent to the medium carbon steel. In most cases impact wear of machine parts made of cast high-manganese steels complicated by several abrasive wear mechanisms including microploughing, microcutting, microcracking, etc. Depending on the geometry of contacting surfaces and corresponding stresses (Shatskiyi (2020), Ropyak et al. (2020a)), as well as abrasive particles shape factors affecting the cutting ability (Onysko et al. (2020), Pryhorovska and Ropyak (2019)), wear mechanisms may change each other, thereby the working surfaces need complex protection. According to Tecza and Glownia (2015), Ayadi and Hadji (2020), abrasion wear resistance of high-manganese steel can be significantly improved by its alloying with some refractory transition metals (Ti, Nb, V, Mo, etc.), which form thermodynamically stable and hard MC-type carbides and/or complex carbides (borides) (Ivanov et al. (2020)). Such type of alloying may cause decreasing of the casting properties by increasing of surface tension and viscosity of steel in liquid phase (Prysyazhnyuk et al. (2015)), which in turn leads to the crack formation during solidification, so the quantity of carbide-forming elements in cast high-manganese steels is limited to a 1-2 wt. %. This leads to the necessity of using cost effective and flexible restoration technologies (Bulbuk et al. (2019)), which are suitable for surfaces working under heavy impact conditions (Moisyshyn and Levchuk (2016), Bazaluk et al. (2021), Ropyak et al. (2020b)). Hardfacing by flux core arc welding (FCAW) with a wire based on high-manganese steel is devoid of such limitations due to features of solidification in thin surface layers, where primary crystallization and refractory phases grain growing does not lead to occurrence of significant internal stresses (Kuskov et. al. (2020)). As it was shown in Shihab et al. (2020) increasing amount of TiC and NbC in powder wires for hardfacing based on high manganese steel allow to obtain surface layers which are characterized by strong metallurgical bonding to the base material without crack formation at the interfaces. According to works by Marinenko et al. (2009), Koval’ et al. (2016), Pukas et al. (2020) multicomponent alloying w ith refractory carbides has several advantages over using monocarbide phases, for instance, increased values of hardness and crack resistance due to formation of interstitial complex carbide solid solutions. Similar approaches can be suitable for carbide alloying systems in materials and coatings based on high-manganese steel, where monocarbides of Nb, Ti, V etc. show rather high thermodynamic stability. In this study, microstructure, phase composition and impact-abrasion wear resistance of the high-manganese steel-based harfacings alloyed with NbC, TiC, VC and Mo 2 C in equimolar amounts have been studied and compared to the coatings, hardfaced with serial high manganese steel electrodes, high speed steel (HSS of R6M5 grade) after standard thermal treatment (Pashechko et al. (2017)) and mild carbon steel of steel 45 grade (St. 45) at the as delivered state. 2. Methods and materials The experimental powder wire used for hardfacing was manufactured by drawing the mixture of ferro-silico manganese, metal manganese, graphite and carbides (TiC, NbC, VC and Mo 2 C) powders into low carbon (of 08kp grade) steel sheath. The ratio between carbide components was set to equimolar, aiming to obtain high-entropy (- like) (Levchuk et al. (2021)) carbide precipitations in the solidified surface layer. The typical chemical composition