Resume PhD (1137131)

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Limited Liability Company"Scientific and Production Association "Geoenergetica"Skazochkin Aleksandr ViktorovichInvestigation of mechanical properties and structurestructural materials, modifiedultradispersed particles of mineralsRESUME OF DISSERTATIONfor the academic degree Philosophy Doctor Higher School of Economics(PhD HSE)Engineering and Applied MathematicsScientific adviser:Doctor of Physical and Mathematical Sciences,ProfessorBondarenko Gennady GermanovichMoscow – 20181The actuality of the research and the statement of the problemThe actuality of the investigation consists in the presence of a problem ofincreased wear of friction pair parts operating in an aggressive environment:abrasives of various origins, thermocyclic loads in a wide range of temperatures,hydrogen sulfide and other gases, sea water, acid solutions.Under these conditions, the wear and corrosion damage of the surface layersof friction units of machines and mechanisms increases sharply, which leads toconsiderable expenses for repair and production of spare parts.

Conventionalstructural materials, providing a general strength of the structure, often do not meetthe requirements of high wear resistance and corrosion resistance. To eliminate and/ or inhibit processes occurring at the metal-environment boundary and adverselyaffecting the performance of materials, various types of surface treatment are used.Such methods of increasing the hardness of metal parts as nitriding,carburizing, other surface modification methods, as well as methods for creatingcoatings, protective films and layers by galvanic methods, methods of heattreatment, ion-plasma treatment, microarc oxidation, gas-plasma spraying andothers. Only methods of modifying the surface to date, several hundred are known.Each of the methods of surface treatment has its advantages and disadvantages, aswell as limitations in the application.

The merits of many of these methods includerelatively low cost, high speed of coating, disadvantages - adhesion problems, theappearance of defects, restrictions imposed by the size of baths, ovens, evacuatedspace, changing the geometry of the part after processing.The shortcomings of many methods can also be attributed to low economicefficiency, since often the processes of creating layers or coatings are accompaniedby long-term high-temperature heating, limiting the mass-size dimensions, and thefragility of the layers obtained. High temperatures can lead to a change in thestructure of the metal, a reduction in strength properties, leashes and a low yield.2Therefore, it is actual to develop other methods for modifying a metal surface withminimal or low thermal impact.One of the effective technologies for creating protective layers on the detailsof friction pairs, in the operation of which showed good results, is the technologyof mineral coatings.

The essence of the technology lies in the creation of amodified surface layer, usually 5-30 μm thick, by its plastic deformation by meansof ultrasonic and mechanical influences, which activate the occurrence ofultradispersed particles of minerals in the metal volume, as well as processes,while protected in know-how mode.Applied research on the development of technology of mineral coatings andthe results of its application at different times were conducted in the followingareas: studies of the properties of mineral materials; research of the properties ofcoatings from mineral materials and the technology of their formation; research ofparameters and characteristics of parts, assemblies and mechanisms with mineralcoatings.Currently, about 80 types of mineral materials are used to createmultifunctional mineral coatings.

The fundamental basis of applied research on theuse of mineral materials for the creation of coatings are works on crystal chemistryand crystallography V.V. Zuev, Yu.V. Kholopov, S.Yu. Lazarev. The types ofmaterials used are determined by the composition and amount of impurities, thestructural-phase state of the constituent components and other characteristics.

Theclassification of natural mineral materials used to enhance the parameters of parts,assemblies and mechanisms has not yet settled and is waiting for its researcherwho has a systemic approach and who has access to information on thecomposition of mixtures.Investigation of the properties of coatings from mineral materials and thetechnology of their formation have been initiated since the creation of the basic3process steps of the technology of mineral coatings. Most of the works are devotedto applied research of properties and parameters of coatings of specific parts andmechanisms, in particular, turbine control units for geothermal stations, bearings,water lubrication, parts of internal combustion engines, parts of turbines, gears andothers.

The mechanisms of wear of concrete parts with mineral coatings, changesin the coefficient of friction of parts, the value of adhesion numbers of a number ofmaterials with mineral coating, and the resistance of coatings in some corrosiveenvironments were investigated.Despite the existing reserve of scientific works on the study of the propertiesof parts exposed to the technology of mineral coatings, it turned out that themicrostructure of the layer modified by the minerals was never investigated.

Untilrecently, it was not known what the metal surface was as a result of the applicationof processes of mineral coating technology: this coating or a modified layer.It should also be noted that to the experimental data published in manyarticles, there are many questions that remain unanswered due to the lack ofimportant details, which leads to the fact that part of the experiments cannot berepeated and correctly interpreted, and also used in calculations. There is aproblem of the correctness of the measurement of the physical and mechanicalproperties of thin coatings and thin modified layers, arising from the presence offactors that lead to methodological errors for some methods of measuring wearresistance, hardness, and modulus of elasticity.

The most significant factors thatintroduce distortion when registering a response are the surface roughness, residualstresses and the effect of the substrate. One of the methods lacking some of theabove drawbacks is the sclerometry method, which has not yet been used tomeasure surface parameters after modification by ultradispersed particles ofminerals. Various physical models of a metal surface modified with mineralparticles and the underlying causes underlying them can be checked, including onthe basis of qualitative experimental data.4Such technology possibilities as the possibility of forming mineral layers oncomplex shape and configuration details, the possibility of surface modification atrelatively low layering temperatures, without changing the geometric dimensions,have determined one more object for application - thread and thread connections ofthe clutch-nipple type from various types of steels, used in shipbuilding, oil andgas production, mechanical engineering, the tribotechnical parameters of whichuntil recently remained unknown.

The urgency of the investigation of the wearresistance of threaded joints with mineral coatings is evident for increasing the lifeof steel parts.Another problem is changing the tribotechnical parameters for local and / orgeneral heating, which can lead to intensification of destructive processes on thesurface and in the volume of the part, which affects its wear resistance and life.Heating during operation and the subsequent acceleration of the wear process, forexample, sliding and rolling bearings, reducers, worm gears and other parts is atypical case that occurs when operating various mechanisms and devices,especially large masses. Therefore, a decrease in the friction coefficient or itsstabilization upon heating, a decrease in the temperature of rubbing metal surfacesis an actual task of material science for practically all industries.

Determination ofthe temperature dependence of the coefficient of friction of a metal part allows insome cases to predict the resource of various details and can serve as a basicexperiment in predicting the properties of various parts with mineral coatings inother cases.The purpose and objectives of dissertation researchThe aim of the work is to obtain new data on changes in the surface structureand near-surface layers, as well as the mechanical properties of a number ofstructural materials (low-carbon steels, titanium and aluminum alloys) modified by5ultradispersed mineral particles to develop effective methods for improving thetribological characteristics of materials and products from them in productionconditions.In the present work several actual practical problems were solved:- obtaining new data on changes in the structure of the metal surface and nearsurface layers of samples from ferritic-martensitic chromium steel and titaniumalloy VT6 (Ti-Al-V) in the creation of mineral coatings;- obtaining new data on the mechanical properties of the titanium alloy VT6 (TiAl-V), modified with ultradispersed particles of minerals, using the sclerometrymethod to minimize the influence of the substrate;- obtaining new data on the temperature dependences of the coefficient of frictionof specimens made of steel modified with ultradispersed particles of minerals, withdifferent surface roughness;- Improvement of tribological parameters of samples from low-carbon steel withmineral coating to determine the possibility of their use in the manufacture of stopvalves;- Improving the tribological characteristics of threaded joints of several types ofsteel pipes, after modification of their surface by particles of minerals, to determinethe possibility of their use in the oil and gas sector.The object of the dissertation research is structural metal materials (lowcarbon steels, titanium and aluminum alloys), modified by ultradispersed particlesof minerals.The subject of the study are the mechanical properties and structure of metalalloys (low-carbon steels, titanium and aluminum alloys) modified with mineralparticles.6Methodological basis of the researchExperimental data were obtained using modern, high-precision andmetrologically certified equipment using standard methods and GOSTs.Microphotographs of the surface structure of the samples were obtained witha Supra 40 scanning electron microscope equipped with an X-Flash EDRS detectorand with the Quantax 4000 software.The surface roughness was measured on a profilometer, model 130, themanufacturing enterprise PROTON MIET.The hardness and modulus of elasticity were measured with a NanoScan-4Dnanodidomer.

The method of measurement is the indentation of a diamondpyramid with registration of an indentation diagram and subsequent calculation ofhardness and elastic modulus in accordance with GOST 8.748-2011 (ISO 14577).The wear resistance was measured using a NanoScan-4D scanning hardness testerusing the sapphire sphere multi-cycle friction method with the control of theclamping force and the tip deepening into the sample.The method of determining the life of a threaded joint of tubing was toconduct multiple tests for screwing-unscrewing the lock of a tubing with theregistration of torque at each stage of the test and the determination of the tightnesswith threaded calibers.The measurement modes and details of the experiments are in thecorresponding sections of the chapters of the dissertation.7Scientific novelty of dissertational research1.

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