Copyright © 2019 V. Aulin, S. Lysenko, A. Hrynkiv, A. Chernai, I. Zhylova, A. Lukashuk This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Problems of Tribologyy, 92 (2) (2019)55-60 Problems of Tribology Website: http://tribology.khnu.km.ua/index.php/ProbTrib E-mail: tribosenator@gmail.com DOI: 10.31891/2079-1372-2019-92-2-55-60 Wear resistance increase of samples tribomating "Steel 45-cast iron SCH20" with geo modifier KGMF-1 V. Aulin1*, S. Lysenko1, A. Hrynkiv1, A. Chernai1, I. Zhylova1, A. Lukashuk 1Central Ukrainian National Technical University, Kropyvnytskyi, Ukraine *E-mail:Aulinvv@gmail.com Abstract Increase of wear resistance of different types of tribomating which are functioning in fluid lubrication is possible due to: choosing more expensive and high quality material of samples that is not always sensible; apply- ing some wear resistant coatings on them; selection and formation of complex composition of oil additives. Due to nanomaterials development there is a possibility of efficient use of functional additives such as geo modifiers in tribology. Due to geo modifier-based oil composites use it’s not necessary to make any structural changes of machines mated parts though their wear resistance is increased. It requires the conducting of some experimental tribological research. It was found that oil media modified by a geo modifier increase the wear resistance of working surfaces of different types of tribomating. The use of geo modifier КGМF-1 (Katerynivka friction geo modifier-1) has been suggested. Samples division into 4 types of mating according to the following characteristic features: mobility, material hardness and friction area has been suggested for more accurate picture of wear resis- tance changes of samples tribomating which are functioning in base and modified oil. Lower friction torque of different samples couplings in modified oil by geo modifier КGМF-1 in comparison with base oil M-10G2K was recorded while using Friction machine 2070 SMT-1 with add-on module "ring-ring". The samples wear rate in modified oil by geo modifier КGМF-1 in comparison with base oil M-10G2K was studied by method of acoustic signal amplitude measurements directly from the friction zone by a commercially produced instrument of Brüel & Kjear company. Moreover, it was recorded that the maximum wear rate of samples in their functioning in modified oil M-10G2K + КGМF-1 was 2...3 times lower, and friction torque change law is similar to the wear rate change depending on the time of testing. Key words: tribomating of sample, geo modifier, composite oil, friction torque, wear resistance, acoustic emission, friction area, oil M-10G2K. Introduction Nowadays the lubricating properties of oils are improved mainly due to commercial additive complexes. Oil additives based on natural minerals after their pretreatment are called geo modifiers. Some papers describing the effect of geo modifiers use admit that surface-active substances of a metal-ceramic reconditioner being used on friction areas with some oil provoke the process of formation of a highly wear resistant metal-ceramic coating with lower friction coefficient on the mated surfaces. Due to these additives in oil medium some friction surface texturing takes place with simultaneous hardening of the main material at great depth on the samples tribomating surfaces. While tribomating is taking place some rational micro relief is being created on the samples surfaces which are correspondent to the actual operating conditions. The distinctive feature of friction geo modifiers from other additives consists in adding some substances to the samples tribomating which launch the self-organization processes [1-4]. At the same time, mainly by add- ing some additives into oil, mated surfaces are being separated by soft metals [5] and long hydrocarbon chains, synthesized film. It contributes to the surface optimal structure developing, especially in the contact areas with maximum number of available bonds resulting in increased oil confinement ability and equilibrium roughness [6]. Literature Review Nonstationary maintenance conditions and high requirements to the machines efficiency along with high 56 Problems of Tribology level of reliability and limited financial expenditures on their maintenance demand from the tribological research to seek for new more efficient ways of wear resistance improvement of different types of oil medium mating [1- 3]. The use of oil additives classification and development of a methodical complex of their choice are high- lighted in many papers [4-6], but it was necessary to study some mating complexes aimed at tribomating wear resistance increase. To decrease the internal friction and to control the laws of external friction of tribomating samples materials it’s possible to use soft metals and their derivative coatings with further highly efficient treat- ment [7-9], but those coatings do not create the possibility of their wear resistance dynamic regulation but they only can control it under certain maintenance conditions. Different types of additives of synthetic and natural origin change the oil physical thermal-oxidative ability due to the formation of materials surface layers enabling to decrease the friction coefficient and additional dissipation of friction energy [10-12], resulted in increased oil lubrication ability but wear resistance does not change greatly. That why it is necessary to seek for some new compositions with more positive characteristics for tribomating. A wide range of tribological characteristics and repairing compositions with additives of natural origin which are based on serpentinite-based powder properties have been studied in the papers [13-16]. The data of conducted investigation haven’t shown the real comparative picture of wear with existing synthetic additives. Although, the authors in papers [13-16] gave some theoretical substantiation of oil compositions use with some friction geo modifiers of this type in tribomating under investi- gation. Geo modifiers stimulate mechanical and chemical reactions, oil components pyrolysis and tribo catalytic carbonization, graphitization and creation of hard carbon containing oil compounds [16,17]. These conclusions can be made due to the study of geo modifiers Mg6Si4O10(OH)8 properties [18]. It was found that friction geo modifiers were based on a large group of minerals with similar chemical formula where Mg can be replaced by iron and nickel [2,13,16]. Serpentinite rock includes several types of serpentinite, magnetite and chromium and various chemical elements used as geo modified composition mixture [10,14]. The study of various geo modi- fied compositions have been highlighted in papers [5,6,10,19], some recommendations have been given dealing with their efficient use in wear-reversing tribo technologies development [15-16]. Chemical constituent of metal-ceramic layer formation from geo modifiers has been developed to a cer- tain extent in the paper [20], but there is no information on physical-mechanical and rheological properties of these layers. Due to this a gap size between parts is getting bigger. Apparently, this happens while a layer is be- ing formed when geo modifiers are in the oil [17,21,22]. Deep investigation of surface and pre-surface layers formed on the friction surfaces under treatment by geo modifiers conditions haven’t been found in open sources. Purpose The purpose of the paper is to increase the wear resistance of samples couplings in oil medium with Katerynivka friction geo modifier-1 (КGМF-1). The purpose has been achieved by solving the problem: find the laws of friction torque change and wear rate of different types of samples mating "steel 450cast iron СЧ-20" due to the use of oil composition M-10G2K + КGМF-1 according to the the scheme “ring-ring” on the friction ma- chine 2070 SMT-1. Research Methodology Steel 45 (HRC52), cast iron СЧ20 (equivalent EN-GJL-200) (НRC40) were used as material samples. The criteria of material choice were their wide use and similarity in parts mating of internal combustion engines of KamAZ-family lorries which are widely represented in central regions of Ukraine and hydraulic units [16]. Motor oil M-10G2K (base oil) widely used for KamAZ-family lorries maintenance and oil composites: M- 10G2K + КGМF-1 (4.0-4.5) were used as a lubricating environment. The preliminary results of КGМF-1 content were described in the paper [2]. We must admit that geo modifier КGМF-1 mixture was obtained from clay- based natural substances, it’s main physical properties were recorded and described by the group of authors of Central Ukrainian national technical university in the patent of Ukraine [23]. Friction machine 2070 SMT-1 (a) with add-on module of "ring-ring" type (Fig. 1) has been used for the study of laws of friction torque change and wear rate of samples mating to find their wear resistance increase and prove the efficiency of oil composites use with geo modifier КGМF-1. Base and composite oils were supplied to the friction zone by a gear pump through a nozzle. A fine filter till particles of 10 mcm size was installed in lu- brication system to avoid wear particles impact on friction and wear parameters. Before the investigation the samples had been wearing in till the complete contact areas took place. Here, the surface roughness was equal to Ra=0.2 mcm that corresponds to wear-in mating of resources defining mating of power units of transport and hydraulic machines. The roughness measurements were made according to GOST 27964-88 using a profilometer (roughness indicator) of make 283. The investigation was conducted with the coefficient of mutual overlap Kb3=0.5, caused by involving more types of samples mating. The samples size and testing procedure were specified by GOST 23.210. Problems of Tribology 57 а b Fig. 1. Friction machine 2070 SМТ-1 (a), with add-on module "ring-ring" (b) The investigation was conducted under 150...250 N load and sliding velocity 0.5...0.7 m/sec that practi- cally corresponds to the contact area of the samples according to GOST Р 51860-2002 of friction machine 2070 SMT-1. The samples of "ring-ring" type have the outer diameter 12 mm, and inner diameter 6 mm. For the friction machine 2070 SMT-1 the mating is divided into 4 types according to the characteristic features: mobility, material hardness, friction zone area (Table 1). Table 1 Types of tribomated samples (parts) and characteristic features. Characteristic features of tribomated samples (parts) Movable sample (part) Stationary sample (part) Type of mating Material hardness, Нр Friction area, Sр Material hardness, Нн Friction area, Sн І Нm > Нf Sm > Sf Нf < Нm Sf < Sm ІІ Нm < Нf Sm > Sf Нf > Нm Sf < Sm ІІІ Нm > Нf Sm < Sf Нf < Нm Sf > Sm ІV Нm < Нf Sm < Sf Нf > Нm Sf > Sm The first type of tribomated samples is widely used where the material of a movable sample (part) is harder (Нр) and friction zone area (Sр) is larger, whereas a stationary sample is less hard (Нн) and its friction zone area (Sн) is smaller. Нр<Нн, Sр>Sн is a characteristic feature of the second type of tribomating, Нр>Нн, Sр