Vol 21, No 4 (2019)
TECHNOLOGY
Investigation of the Technology of Microdosed supply of Lubricant Compositions with Nanoparticles during Grinding of Heat-Resistant Ni-based with Additional Air Cooling
Abstract
Introduction. In terms of environmental issues, the most significant problem in the metal finishing process is the use of lubricating cooling fluids (coolant). As an alternative of coolant using in the world practice are integrating an environmentally determined engineering of minimum lubrication (MQL – minimum quantity lubrication). Though the use of MQL process in the abrasion with the highest contact temperatures is not effective enough. Due to this a set of measures has been suggested in the scientific community such as, the additional cooling action of the cutting area by cold air (CAMQL – cold air with minimum quantity lubrication). As part of our paper the researches of using these methods, both separately and in synthesis, in order to assessment of capability for increasing the MQL efficiency when grinding Ni-based alloy are carried out. The purpose of the work is to quantify the influence of the MQL and CAMQL input processes on the operational factors of the grinding process and the properties of a thin surface. Vegetable soy oil is used as a lubricant, including the addition of Al2O3 nanoparticles. Research methods. The surface roughness is controlled with Mitutoyo Surfest SJ-410 profilometr. Component cutting forces are measured using a six-component force-measuring complex Amti MC36-1000. Elemental analysis and surface morphology rating are carried out using a FEI Versa 3D LoVac dual-beam raster electron microscope with an X-ray microanalysis attachment. The contact potential difference is measured by atomic-force microscopy using the Kelvin’;s probe method. Results and discussion. The better application conditions for MQL and CAMQL are established, these are the dosing regimens of lubricating at 30 ml/h and the air low range for CAMQL equals to 12 m3/h. The measurement results of cutting forces showed the using of soy oil lubricant only is more effective for CAMQL. On addition of Al2O3 nanoparticles with an optimal concentration of 0.4 wt. % there is observed the dramatic decline of the cutting forces, in particular Py component (by 30 % relative to grinding process without coolant), and the force values are almost the same when using both MQL and CAMQL. The machined surface roughness is reduced averagely 1.5 times. While using lubricant compositions with nanoparticles, there is a tendency to lower the surface roughness values when grinding with CAMQL. The states research of a thin surface layer after grinding process showed the use of CAMQL, regardless of the lubricant type, provides reduction of surface oxidation and improvement of its properties. When using compositions with Al2O3 nanoparticles, the decrease of adhesive interaction traces of machine surface is observed.
Obrabotka Metallov / Metal Working and Material Science. 2019;21(4):6-18
6-18
Production Amorphous Coatings by Electrospark Treatment of Steel 1035 in a Mixture of Iron Granules with CrMoWCBSi Powder
Abstract
Introduction. Metallic glasses are of interest to researchers as materials that can be used as protective coatings for metals and alloys. The study of new methods for forming coatings made of metallic glass is an urgent task. Purpose: to study the conditions of formation and properties of metallic glass coatings obtained by the method of electrospark treatment of steel 1035 in a mixture of iron granules and a multicomponent powder mixture consisting of chromium, tungsten, molybdenum, silicon, boron and carbon. Methods. The powder mixture had an average particle size of 0,3 μm. The volume fraction of the powder in the mixture with granules varied from 2,5 to 9,3 vol. %. Coatings are deposited at pulse energy of 0,33 J with a frequency of 1 kHz for 8 minutes in argon. The composition and structure of the coatings are studied by X-ray diffraction analysis, scanning microscopy, and energy dispersive analysis. Results and discussion. The average thickness of the coatings is in a narrow range of 41…43 microns. The proportion of the amorphous phase in the coatings ranges from 78 to 95 vol. %. The distribution of elements over the coating cross section is uniform. With increasing powder content in the mixture of granules, the iron concentration in the coatings decreases from 60 to 41 at. %. In this case, the ratio of the remaining elements in the composition of the coatings corresponds to the composition of the multicomponent powder, which indicates the uniform participation of powder particles of different grades in the formation of the deposited coatings. The wear rate of samples with coatings in the dry sliding mode is in the range 0,7…5,9 × 10–5 mm3/Nm, which is 2,5…6,5 times lower than that of steel 1035 without coating. The cyclic corrosion resistance of samples with coatings at a temperature of 700 °C for 100 hours of testing is 15…30 times higher than that of steel 1035, which is explained, first of all, by the presence of chromium and silicon in the coatings.
Obrabotka Metallov / Metal Working and Material Science. 2019;21(4):19-30
19-30
EQUIPMENT. INSTRUMENTS
The Dependence of Tool Wear and Quality Parameters of the Surface being Cut on Dynamic Characteristics
Abstract
Introduction. It is known that the wear and quality of the parts surface change during the cutting process. These changes depend on the dynamic cutting system. Studies are also known in the field of the dynamics of the cutting process, in which stability problems of various attractive sets of deformation displacements formed in the vicinity of the trajectories are considered. The bifurcations of attracting sets are analyzed, including those associated with the release of energy in the cutting zone. However, a study of the relationship between the evolutionary restructuring of the system and the output properties of the cutting process in the unity of the wear rate of the tools and the geometric surface topology formed by cutting is not performed. The provisions of evolutionary transformations of a dynamic cutting system for the case of analysis of the output characteristics of the cutting process are developed in the paper. The purpose of research is to disclose the relationship of the evolutionary adjustment of the dynamic cutting system with the tool wear resistance and a change in the geometric topology of the surface formed by cutting to ensure the required output processing characteristics. A method is proposed, and the results of studying changes in the wear rate, the amount of wear, and changes in the geometric topology of the surface formed by cutting depending on the initial technological conditions and the dynamic parameters of the system during evolutionary adjustment are presented. The research methods are: mathematical simulation of evolutionary transformations based on the representation of the dependence of the dynamic coupling parameters formed by the cutting process, in the form of its dependence on the power path of irreversible transformations at the interface nodes of the tool faces with the workpiece and the cutting zone. In this case, the conversion of power into the tool wear rate and the change in the geometric surface topology are considered. Results and discussion. Dependences of wear and surface geometry on the evolutionarily changing properties of a dynamic cutting system are disclosed. The task is to coordinate the designed trajectories with the internal evolutionally changing dynamics of the system to increase processing efficiency. The research results are promising especially for processing parts with complex geometric profiles, as well as parts whose stiffness matrices vary along the tool path.
Obrabotka Metallov / Metal Working and Material Science. 2019;21(4):31-46
31-46
Synthesis of the Motion Law of Filling Threads Beat-up Mechanisms of the STB Loom with Cam Driven
Abstract
Introduction. The paper considers the design of the filling threads beat-up mechanism for the STB type loom. The analysis of scientific literature in the field indicates that the wide range of fabrics production at high speeds requires providing the initial period of the mechanism movement with an additional area on the cam profile which allows reducing the impact load at the time of clearance adjustment in the pair of cam-roller. In this case, the designer needs to synthesize an acceleration law which should be task-specific and provide for a certain production step. This study is relevant since the existing synthesis methods of the filling threads beat-up mechanism fail in providing the basis for modernization of the mechanisms whose work depends on the main one (beat-up mechanism). The performance of such mechanisms can be increased only after significant changes in their cycle charts. Objective: synthesis of the new motion law of the filling threads beat-up mechanism (slay mechanism), allowing to reduce the load on the follower in the initial period of its movement. The paperinvestigates the motion law of the beat-up mechanism with an additional section of the cam profile which allows imparting additional movement to the follower at the moment of its initial movement. Research Method: designing the slay mechanism drive with form-fit cams using software packages application. Results and discussion. The conducted research allowed proposing the method of motion law synthesis for slay mechanism. We suggest introducing an additional section at the cam profile. The laws of displacement change are obtained by integrating the acceleration curve. Theoretical studies are brought to numerical values of the slay mechanism's follower accelerations and displacements.
Obrabotka Metallov / Metal Working and Material Science. 2019;21(4):47-58
47-58
MATERIAL SCIENCE
Hydrothermal Deposition of С/MoS2 on Electrospark Fe-Al Coatings for AISI 304 Stainless Steel
Abstract
Introduction. Improving the tribological properties of stainless steels can be achieved by creating anti-friction coatings. The purpose of the work is a research of the structure and wear resistance of composite electrospark coatings made of Fe-Al intermetallic compounds with pores filled with C/MoS2. Methods. In this work, the coatings of Fe-Al intermetallic compounds are obtained on AISI 304 stainless steel by the method of electrospark deposition in a mixture of granules consisting of iron and aluminum. Five mixtures of granules with aluminum content from 20 to 100 mol % are prepared. In order to increase the porosity of intermetallic coatings, it was etched in a 20% alkali solution. To fill the porous surface of samples with amorphous carbon and molybdenum disulfide, the method of hydrothermal synthesis is applied in two stages: in a glucose solution at 160 °C, and in a solution of thiourea and sodium molybdate at 220 °C. The structure of the coatings is studied by X-ray diffraction analysis, scanning electron microscopy, X-ray microanalysis and Raman spectroscopy. The wear resistance of the coatings is investigated according to ASTM G99-04 technique with dry sliding friction using counter bodies in the form of disks made of high-speed steel R6M5 at a speed of 0.47 m/s under loads of 10 and 50 N. Results and discussion. It is established that with an increase of the aluminum content in the granules mixture, the phase composition of intermetallic coatings changes from FeAl to Fe14Al86. It is shown that the etching of intermetallic coatings is accompanied by the expansion of transverse cracks and the appearance of pores that further are filled with carbon and with molybdenum disulfide. Friction coefficient is in range of 0.26-0.46. The wear rate of Fe-Al-C-MoS2 coatings is in the range of 1.1-9 × 10–5 mm3/Nm, which is 3-22.5 times lower than one of AISI 304 steel. The best wear resistance is expectedly demonstrated by coatings prepared in the medium of granules with the highest aluminum content.
Obrabotka Metallov / Metal Working and Material Science. 2019;21(4):59-69
59-69
Effect of Laser Alloying with the Powder Mixtures of Cu–Zn–Ti and Si–Cu on the Structure and Properties of Cast Aluminum Alloy
Abstract
Introduction. The use of laser based modification technologies is an actual and promising way to improve the surface properties of aluminum alloys. Laser alloying of aluminum alloys, which helps to improve its corrosion resistance, mechanical properties and wear resistance under conditions of adhesion and abrasive wear, is of great interest. The aim of this work is to study the possibility of increasing the physical and mechanical properties of the cast aluminum alloy by laser alloying with the powder mixtures of Cu–Zn–Ti (blend no. 1) and Si–Cu (blend no. 2), which are applied to the surface of specimens in the form of coatings. Laser alloying of the surface of specimens is carried out on a continuous CO2 laser with the emission wavelength λ = 10.6 μm. The methods of investigation. Optical and scanning electron microscopy, energy-dispersive microanalysis, x-ray diffraction phase analysis, microhardness measurement, instrumented microindentation, abrasive wear and thermal erosion tests are used. Results and discussion. It is established that the laser alloying results in the formation of alloyed layers with a depth h = 3.5–4.0 mm on the surface of the aluminum alloy specimens. The alloyed layers have a dendritic-cellular structure, the main structural components of which are the α–Al solid solution and a network of eutectic silicon crystals along the boundaries of dendritic cells. The CuAl2 intermetallide with a particle size of 1–5 μm also is detected in the structure of the alloyed layers. The laser alloying increases the hardness of the aluminum alloy from 90 to 125 HV0.025 after alloying with the powder blend no. 1 and up to 100 HV0.025 after alloying with the powder blend no. 2. According to the microindentation data, the alloyed layers are characterized by increased resistance to elastic-plastic deformation, which is evidenced by the increase in the parameters of Re in 1.2–1.38 times, HIT/E* in 1.33–1.67 times and in 2.14–3.71 times. Wear resistance tests under conditions of abrasive wear shows that the laser alloying leads to some increase in wear rate Ih (decrease in wear resistance) of the aluminum alloy from (1.49±0.09)×10−3 to (1.82±0.06)×10−3 after alloying with the powder blends no. 1 and 2. However, laser alloying the alloy leads to an increase in its resistance to thermal erosion, which manifests itself in reducing the number and size of thermal cracks.
Obrabotka Metallov / Metal Working and Material Science. 2019;21(4):70-84
70-84
Structure and Properties of Copper Compensator Joints obtained by Hybrid Friction Stir Welding Technology
Abstract
Introduction. Special copper compensators are used to compensate for temperature expansion, vibrations and the resulting dangerous deformations on power live conductors. Application of compensators for current-carrying elements allows to increase reliability, durability and safety of power electrical devices operation. However, now for compensators manufacturing the technology of the manual soldering is used, which lacks are low productivity, the limited sizes of received products, and also dependence of products quality on the personnel qualification. In this connection, the actual task is to develop new promising methods of obtaining copper compensators. Such methods include friction stir welding. This type of permanent joints formation is widely used in the shipbuilding and automotive industries, production of missile bodies for aerospace, and others. Friction stir welding was developed primarily for the production of permanent joints of thermally hardenable aluminum alloys, but it is also used for welding of thermally non-hardenable aluminum alloys, titanium alloys, steels and copper. Theoretical and experimental studies of friction stir welding of copper demonstrate the high ability of this technology to produce permanent joints from copper and its alloys. The purpose of the present work was to reveal the peculiarities of the structure and mechanical properties of copper compensators produced by friction stir welding. Results and discussions. The carried out researches have shown, that at friction stir welding of copper monolithic plate with copper foil, preliminary connected by soldering in a package, allows to receive a joint without formation of undesirable intermetallic compounds. Solder layers are mixed in the weld, and the distribution of solder in the stir zone is uneven. Microhardness and elemental microanalysis data showed that the retreating side of the joint contains the largest number of solder layers. The structure of the foil package has not changed after welding, so that the conductivity of the material has not changed either. Tensile tests have shown that the compensator is not fractured by the weld, but by successive rupture of the copper foil, which allows the damaged element to be identified in advance.
Obrabotka Metallov / Metal Working and Material Science. 2019;21(4):85-93
85-93
Regularities of Composite Materials Formation using Additive Electron-Beam Technology, Friction Stir Welding and Friction Stir Processing
Abstract
Introduction. At the present time, among the methods of obtaining polymetallic structures of great importance are the technologies of solid-phase and liquid-phase materials production, as well as the ways of combining different methods and using hybrid technologies. In this connection, it is necessary to carry out complex comparative research tests of structural-phase changes in the materials obtained by different methods from dissimilar metals and alloys. The purpose of this work is to obtain polymetallic structures of "copper-aluminum" system by different methods and to study the structural-phase state of the materials. The structure of copper-aluminum polymetallic samples formed by friction stir welding, friction stir processing and additive electron-beam wire-feed technology has been studied. The methods as optical microscopy, scanning electron microscopy and microhardness measurement were used in the study. Results and discussions. Different features of solid solutions and intermetallic phases formation in materials at various technological processes are revealed, and peculiarities of defects formation depending on technological methods of samples formation are determined. Possibilities of obtaining samples with a composite structure including hardening intermetallic particles in the metal matrix by different manufacturing and processing methods are determined. The received data testify to the formation of intermetallic phases of higher hardness in the boundary layer area during the mixing of the system components in the liquid state under the additive electron-beam technology conditions. Distribution of intermetallic components is more uniform at friction stir processing of copper and aluminum sheet metal package with an arrangement of aluminum alloy sheet in the upper part. The least hard intermetallic phases are formed during friction stir welding. Overheating of the system and sample destruction is possible with different positions of copper and aluminum alloy sheets during friction stir welding and processing. The heterogeneous structure of the stir zone of the system components during friction stir welding is determined by different conditions on the advancing and retreating sides of the sample. The structure of the stir zone of the heterogeneous materials sample is similar to that formed during friction stir welding of homogeneous materials and is represented by a vortex structure with alternation of different system components layers. Intensive diffusion interaction of aluminum alloy and copper during friction stir processing leads to the introduction of solid solutions and intermetallic phases to a significant depth in the heat-affected zone of copper sheet. Sample destruction due to the defect formation in the form of different scale level cracks at additive electron-beam technology occurs mainly in the zone of the hardest intermetallic phase formation along the boundaries of various structural components.
Obrabotka Metallov / Metal Working and Material Science. 2019;21(4):94-112
94-112
Damask Steel Mechanical Properties
Abstract
Purpose: to determine the mechanical properties of damask steel, to establish the main disadvantages and advantages of blade products of antiquity compared to modern high-carbon tool steels. Materials and research methods. The objects of the study are tool steel U15A (1.5 % С) and damask steel Ds15P. The chemical composition of the materials is determined using an ARL 3460 type optical emission spectrometer. Structural studies are carried out on a Zeiss EV050 XVP scanning electron microscope with an EDS X-Act probe microanalyzer system and a METAM PB-21-2 optical microscope. The structure of the excess carbide phase is studied using a transmission electron microscope of the TEI Tecnai G2 20 TWIN type. The structural component hardness is determined using a Model 402MVD microhardness tester. Results and discussions. Scientific works to determine the mechanical properties of genuine Damascus steel are very few. This is because most high-quality blades of genuine Damascus steel sword are stored in state museums or private collections. The authors agree that genuine Damascus steels with a carbon content of 1.3% to 2.3 % have legendary elasticity and fracture toughness with a sufficiently high content of phosphorus in the composition of these steels. The paper compares the mechanical properties of modern carbon tool steel and genuine Damascus steel. It is confirmed that the layered structure of Eastern Damascus steel type Ds15P, formed carbide layers of a width not exceeding 75 microns in troostite matrix differs from the homogeneous structure of modern carbon tool steel type U15А. The microhardness of the carbide layers in genuine Damascene steel is 920 HV, the microhardness of the layers troostite - 475 HV. Carbide layers in genuine Damascene steel consist of cementite oblong. Oblong excess carbides morphologically resemble an oval with a thickening in the middle part. The sizes of carbides in cross section make about 3...4 microns, in longitudinal section do not exceed 9...12 microns, the ratio of axes makes 1/3. Found that the blade edge Damascus blade represents microsaw consisting of parallel carbide and troostite layers. Conducted comparative tests on the preservation of cutting edge blade steel U15А and Ds15P found that with little effort Damascus steel (Ds15P) shows a greater number of cuts than the steel U15А. It is revealed that a layered structure of genuine Damascus steel type Ds15P the fatigue crack propagation from the time of its occurrence until complete destruction occurs for a greater number of cycles than in the homogeneous structure of modern carbon tool steel type U15А. Damascus steel type Ds15P showed a 2-fold stock fatigue life compared to modern carbon tool steel type U15А.
Obrabotka Metallov / Metal Working and Material Science. 2019;21(4):113-126
113-126