Vol 26, No 4 (2024)
- Year: 2024
- Articles: 14
- URL: https://bakhtiniada.ru/1994-6309/issue/view/19308
- Description:
Full Issue
TECHNOLOGY
Investigation of vegetable-based hybrid nanofluids on machining performance in MQL turning
Abstract
Introduction. Vegetable-based hybrid nanofluids are increasingly important in the context of Minimum Quantity Lubrication (MQL) turning due to its enhanced lubrication properties and environmental benefits. These nanofluids, which typically combine vegetable oils with nanoparticles like graphite or titanium dioxide, improve machining performance by reducing friction and cutting forces, leading to better surface finish and tool life. The purpose of the work. Coated carbide tools are widely used for machining SS 304 stainless steel due to its wear resistance and high temperature resistance. The purpose of the current work is to evaluate the machining performance of SS 304 steel under different concentrations of hybrid nanofluids. The methods of investigation. In this study, an attempt was made to use copper oxide/aluminum oxide (CuO/Al2O3) hybrid nanoparticles mixed with corn oil. A total of six hybrid cutting fluids with 100 ml volume and different mass concentration (0.4 %, 0.8 %, 1.2 %, 1.6 %, 2 %, and 2.4 %) were developed and its performance on SS 304 steel was investigated. Results and discussion. The finding revealed that with an increase in the mass concentration, the thermophysical properties improve. In addition, it is shown that friction decreases with an increase in the particle concentration to 1.6 wt. %. At a concentration of 1.6 wt. % of CuO/Al2O3 hybrid cutting nanofluid showed the best performance characteristics. This study also provides a comparison with dry turning. The highest tool wear was observed in dry turning, followed by turning using corn oil. A 32 % reduction in cutting force is observed. The surface roughness when using CuO/Al2O3 hybrid cutting nanofluid is reduced by 27.7 %. However, when using a hybrid nanofluid (2.4 % of CuO/Al2O3), low tool wear is observed. In this study, the possibility of using vegetable-based hybrid nanofluids for metal turning with a minimum amount of lubricant is considered.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):6-18
6-18
Impact of print orientation on wear behavior in FDM printed PLA Biomaterial: Study for hip-joint implant
Abstract
Introduction: hip joint replacement surgery involves replacing the damaged joint with an implant that can re-create the joint's articulation functionality. 3D printing technology is more promising than the traditional manufacturing process when it comes to producing more complex parts and shapes. The goal of the current research project is to determine how quickly biomaterial implant can be manufactured using 3D printing for hip-joint replacement by studying the wear rate of parts manufactured using different printing orientations. Although there are several additive manufacturing technologies, fuse deposition modeling (FDM) technology has had a significant impact on healthcare, automotive industry, etc. This is mainly due to the adaptability of different polymer-based composite materials and its cost-effectiveness. Such 3D printed polymers need to be further studied to evaluate the wear rate depending on different 3D printing orientations. Polylactic acid (PLA) biomaterials were extensively studied to determine its suitability for use as hip joint materials. Purpose of the work: in this work, an experimental study was carried out on the effect of printing orientation on dry sliding wear of a polylactic acid (PLA) material obtained by fused deposition modeling (FDM) technology using the pin-on-disk (SS 316) scheme. In addition, experimental and empirical models are developed to predict the performance taking into account the influence of load and sliding speed. Grey relational analysis was used to determine the optimal parameters. The methods of investigation: the FDM printing was used to manufacture pins using different printing orientations. Printing direction refers to printing at angles of 0°, 45°, and 90°, while all other 3D printing parameters remained unchanged. Wear testing was performed using the pin-on-disk kinematic scheme. During the experiments, the normal pin load and disk rotation speed were varied. The experiments were methodically designed to study the effect of input parameters on the specific wear rate. About 13 experiments were conducted for each printing orientation with a friction path of 4 kilometers, in the load range of 400–800 N, at a sliding speed of 450–750 rpm. Result and discussion: the study provides important results especially regarding the direction of 3D printing of components. It was found that the lowest sliding wear was observed for the pin printed at an angle of 0°, while slightly higher wear was observed for the pin printed at an angle of 90°. The layer bonding in the pin printed at an angle of 45° deformed under higher load, mainly due to an increase in temperature. The low bond strength in the pin printed at an angle of 45° resulted in high sliding wear. The optimal result was achieved at a sliding speed of 451 rpm and a load of 600 N. The results of the study are very useful for choosing materials for 3D printing of biomedical implants, medical and industrial products.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):19-40
19-40
Geometry distortion, edge oxidation, structural changes and cut surface morphology of 100mm thick sheet product made of aluminum, copper and titanium alloys during reverse polarity plasma cutting
Abstract
The introduction describes the feasibility of using reverse polarity plasma cutting to produce large-sized non-ferrous metal blanks up to 100 mm thick. Data on the use of plasma cutting with direct and reverse polarity currents for thick sheet metal and the main technological problems associated with its implementation are presented. The purpose of the work is to study the organization of the structure and properties of the near-surface zone, changes in the chemical and phase composition when cutting aluminum, copper and titanium alloys. The research methods are optical and scanning electron microscopy, microhardness measurement, X-ray diffraction and energy-dispersive analysis. Plasma cutting was carried out using air as a plasma-forming and shielding gas, simultaneously with water injection into the discharge chamber and the formation of a “water fog” around the plasma column. Results and discussion. It is shown that both the arc stability and the shape of the plasma column are of great importance in reverse polarity plasma cutting of rolled sheets. The distortion of the cutting geometry during normal operation is greatest in the central part, and with insufficient heat input it shifts to the lower part and increases significantly. The operation of the plasma torch in air does not lead to significant changes in the composition of the cutting surface of aluminum and copper alloys. A decrease in the magnesium content near the edge is typical for the aluminum alloy in the surface layers. Cutting of the titanium alloy is accompanied by intense oxidation of the surface, especially in areas of difficult metal displacement from the cutting cavity. The formation of titanium oxides, mainly rutile Ti2O, sharply increases the microhardness values in the surface layers, which negatively affects the machinability of the cutting edge and requires shot blasting to remove the oxide layer. The conclusion describes the main patterns of implementing reverse polarity plasma cutting of sheet metal from aluminum, copper and titanium alloys with a thickness of 100 mm.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):41-56
41-56
Comparative evaluation of roller burnishing of Al6061-T6 alloy under dry and nanofluid minimum quantity lubrication conditions
Abstract
Introduction. Roller burnishing is one of the most popular methods for improving the surface quality of a workpiece, increasing its wear resistance, microhardness and corrosion resistance. During the processing, the workpiece is compressed and smoothed under the pressure of hardened roller. Purpose of the work. The results of the research show that the introduction of minimum quantity lubrication (MQL) during roller burnishing makes it possible to increase the efficiency of the process by reducing friction and improving lubrication. Studies have shown that the use of nanofluids under MQL conditions improves the machining performance. However, very little attention has been paid to the roll burnishing of Al6061-T6 alloy under nano minimum quantity lubrication (NFMQL) conditions. The methods of investigation. In light of this, this study compares the performance of roll burnishing of Al6061-T6 alloy under dry friction conditions and NFMQL conditions. The microhardness, roundness, and surface roughness are evaluated, modeled, and optimized in the study by considering the cutting speed, feed rate, and number of passes. Based on the experimental results, mathematical models are established to predict the surface roughness, microhardness, and roundness deviation. Results and Discussion. The developed models of surface roughness, microhardness and roundness deviation show the R-square value higher than 0.9, which allows these models to be confidently used to predict the studied responses under dry friction conditions and under NFMQL conditions within the parameter domain selected in this work. According to this study, the machining performed in four passes at a cutting speed of 357 rpm and a tool feed of 0.17 mm/rev can obtain the lowest roundness deviation (3.514 μm), the best microhardness (130.19 HV) and the lowest surface roughness (0.64 μm). Further, the study shows that increasing the number of passes (more than four) does not lead to a significant improvement in surface roughness or microhardness. However, it leads to a slight increase in roundness deviation. Therefore, it is recommended to use a maximum of four passes during roll burnishing of Al6061-T6 aluminum alloy specimens under dry friction conditions to achieve optimal results. The obtained results imply that roller burnishing can effectively improve the overall surface quality and hardness of the workpiece. In addition, roller burnishing is regarded as an affordable method to enhance the functionality and strength of the machined parts by reducing the occurrence of surface defects such as scratches and cracks. It is found that the surface roughness decreases with the increase of the cutting speed. However, it is observed to increase under both dry friction and NFMQL conditions when the cutting speed is increased to 360–380 rpm. Moreover, it is found to decrease with the increase of the feed and the number of passes. But after three or four passes at a feed rate of 0.2–0.25 mm/rev, a noticeable increase in the surface roughness is observed. It is noticed that with the increase of the feed, the microhardness and the roundness deviation increase. In addition, as the number of passes increases, the roundness deviation decreases and the microhardness increases. The number of passes under dry friction condition and feed rate under NFMQL rolling has significant effects on the surface roughness. The cutting speed seems to have the greatest effect on the microhardness, followed by feed rate and the number of passes. On the other hand, the effect of increasing microhardness under NFMQL conditions seems to be stronger. Under dry friction condition, the cutting speed has a significant effect on the roundness deviation, and under NFMQL conditions, the feed rate has an effect.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):57-74
57-74
Assessment of the quality and mechanical properties of metal layers from low-carbon steel obtained by the WAAM method with the use of additional using additional mechanical and ultrasonic processing
Abstract
Introduction. Additive manufacturing is a technology that enables three-dimensional (3D) components to be printed layer by layer according to digital models. Completely different from traditional manufacturing methods such as casting, forging, and machining, additive manufacturing is a near net shape manufacturing process that can greatly enhance design freedom and reduce manufacturing runtime. The material processing challenges in Wire and Arc Additive Manufacturing (WAAM) are related to achieving performance metrics related to geometric, physical, and material properties. Tight tolerances and stringent surface integrity requirements cannot be achieved by utilizing stand-alone AM technologies. Therefore, WAAM parts typically require some post-processing to meet requirements related to surface finish, dimensional tolerances and mechanical properties. It is therefore not surprising that the integration of AM with post-processing technologies into single and multi-setup machining solutions, commonly referred to as hybrid AM, has become a very attractive proposition for industry. The purpose of the work is to evaluate the quality and mechanical properties of the resulting metal layers of mild steel by WAAM method using additional mechanical and ultrasonic processing. Research Methods. To conduct the experiments, a set of welding equipment was used — a single-phase inverter device KEMPPI Kempomat 1701, designed for welding with wire in shielding gases. A mixture of argon and carbon dioxide (80 % argon and 20 % CO2) was used as a shielding gas. SV-08G2S (0.8 C-2 Mg-Si) wire was used as the surfacing material. A plate made of steel St3 with overall dimensions 150×100×5 mm was used as a base for surfacing. The surface of the plate before surfacing was thoroughly cleaned from the layer of oxides, oil, rust and other contaminants. For this purpose mechanical cleaning of the surface was used with BOSCH abrasive wheel with a diameter of 125 mm diameter and a grit size of 120. Before surfacing the surface of the product was degreased with white spirit. The gas flow rate was set at 8 dm3/min. To select the optimal wire feed rate and volt-ampere characteristic, surfacing was performed at each adjustment step of wire feed rate, and voltage. Mechanical statistical tensile tests, chemical composition analysis and metallographic studies were also performed. Results and Discussion. Gas porosity is a typical defect that occurs during the WAAM process and should be eliminated because it adversely affects the mechanical properties. Initially, gas porosity leads to a reduction in the mechanical strength of the part due to damage from microcrack formation. In addition, it often causes the surfaced layer to have worse fatigue properties due to the spatial distribution of different shape and size structures. In our experiments we found that a wire feed speed range of 5–6 m/min is optimal. Increasing the flow rate of shielding gas in the range of 8–14 l/min allows reducing porosity in the surfaced metal to almost zero. The mechanical properties of the surfaced beads show that the average value of yield strength after machining is higher than that of unprocessed specimens. The data obtained from these experiments are in good agreement with those reported in the literature. The presented results can be used in real WAAM technological processes.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):75-91
75-91
EQUIPMENT. INSTRUMENTS
Systematics of multi-tool setup on lathe group machines
Abstract
Introduction. The analysis of factory lathe-automatic operations revealed a significant variety of multi-tool setups and identified its areas of application. To develop a matrix theory of accuracy for multi-tool machining and create a unified algorithmic approach to errors modeling for all possible spatial multi-tool setups, it is necessary to consider the flexibility of the technological system in all coordinate directions. In this regard, it is required to systematize a large number of existing multi-tool setups and classify it to structure the information and improve the understanding of its application. Purpose of the work is to develop a classification of multi-tool setups on multi-carriage and multi-spindle CNC lathes, enabling the creation of both a matrix model of machining accuracy for each classification class and a unified generalized matrix model of machining accuracy for the entire classification class. The work investigates the systematics of multi-tool setups, oriented toward the development of matrix models of machining accuracy. Therefore, the classification considered in this work is aimed at identifying the characteristics of force loading and deformation of the technological system during multi-tool machining. The research methods involve identifying the parameters used for classification and the hierarchy of these parameters, which determines the levels and order of the systematics. Based on the principles of systematics of multi-tool setups used in traditional automatic lathes, an analysis of its adaptation to the capabilities of modern lathes designed for multi-tool machining is conducted. Results and discussion. As a result of the research, a formalized six-level classification of multi-tool setups is developed, which includes the following aspects: the method of workpiece mounting, the set of carriages, the types of cutting tools, the types and directions of carriage feeds, the orientation of cutting tools relative to the workpiece, and the method of tool engagement (parallel, sequential). This classification takes into account the technological capabilities for organizing multi-tool machining on modern CNC lathes. The main classes of the proposed systematics of multi-tool setups in the presented work include single-carriage single-coordinate setups, single-carriage two-coordinate setups, dual-carriage single-coordinate setups, dual-carriage two-coordinate setups, and multi-carriage setups. The proposed systematics of multi-tool setups on lathe group machines is aimed at developing machining accuracy models and can serve as a basis for developing recommendations on cutting modes for these CNC machines. The proposed classification of multi-tool setups forms the foundation of the methodological support for the CAD system of lathe-automatic operations and serves as the basis for creating next-generation CAD systems for lathe operations.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):92-111
92-111
Increasing the durability of drill bit teeth by changing its manufacturing technology
Abstract
Introduction. The development of the mining industry requires increasing the durability and safe tool performance life. For bits of mining drilling machines, this problem is often solved by improving the material of the teeth of these bits. The paper presents the results of a study on the development of a technology for the manufacture of hard-alloy drill bits with increased wear resistance and testing of prototypes when drilling hard rocks. Changes in technology have led to changes in the shape of the tooth. Also, purer tungsten powder was used as the initial component. Research methods. The paper studies carbide teeth of bits manufactured at JSC Almalyk Mining and Metallurgical Combine using standard and modified technology. Its structure and chemical composition were studied. Results and discussion. New methods for performing technological operations for the manufacture of carbide teeth (pins) and steel pin bits are developed and mastered. Tungsten-cobalt teeth were manufactured using VK10KS (90 %W; 10 % Co) hard alloy, produced using tungsten carbide powder synthesized by carbidization of purified tungsten powder. The shape of the tooth surface was changed from ballistic to semi-ballistic. Metallic cobalt powder was used as a binder. Pin bits of the KNSh40×25 type are made of 0.35 C-Cr-Mn-Si steel. Tests of experimental bits were carried out at several mines, as a result of which its suitability for drilling rocks with a hardness of f` = 14–18 was established. The results of industrial operation showed that the durability of the teeth of bits manufactured by JSC Almalyk Mining and Metallurgical Combine is not significantly inferior to bits from European manufacturers. At the same time, the cost of such bits is several times lower.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):112-124
112-124
Investigation of the distribution of normal contact stresses in deformation zone during hot rolling of strips made of structural low-alloy steels to increase the resistance of working rolls
Abstract
Introduction. During the operation of the working rolls of the finishing groups of continuous wide-strip hot rolling mills, normal contact stresses have a decisive influence on its resistance and strength, especially when rolling a range of low-alloy structural steels with a minimum thickness range of 5.5–2.0 mm, which does not correspond to the passport characteristics of such mills. The subject of the study. Previously performed studies of the stress-strain state of the rolled strip in the deformation zones make it possible to estimate the level of normal contact stresses acting on the working rolls during hot rolling of strips of low-carbon steels. The paper discusses the results of the study of the stressed state of strips of low-alloy structural steels in contact with rolls, taking into account the features of the chemical composition of the metal and changes in its elastic properties during deformation at hot rolling temperatures. The results obtained are applicable to the evaluation of the contact strength of the finishing rolls of the rolling mill. The purpose of the work is to investigate the distribution of normal contact stresses in the deformation zones during hot rolling of strips of low-alloy structural steels to ensure high resistance of the working rolls. Material and methods. The study is based on the elastic-plastic model and equations for calculating normal contact stresses for each section of the deformation zone. The specificity of variation of Young's modulus (modulus of elasticity) of low-alloyed structural steels in accordance with certain hot rolling temperatures is studied in detail, and the contact strength of high-chromium cast iron work rolls is evaluated. Results and discussion. A reliable regression equation is obtained for determining the values of the Young’;s modulus of the rolled strip as a function of changing hot rolling temperatures. The results of a numerical experiment are presented in the form of calculating the maximum normal contact stresses using the elastic-plastic model of the deformation zone and assessing the contact strength of the work rolls based on actual rolling conditions on an operating mill. New improved technological modes of hot rolling of low-alloy structural steels (0.1 C-Cr-Si-Ni-Cu, 0.18 C-Cr-Mn-Ti and 0.14 C-2 Mn-N-V) are proposed, which make it possible to reduce the maximum contact stresses and increase the resistance of the working rolls.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):125-137
125-137
Manufacturing of tool electrodes with optimized configuration for copy-piercing electrical discharge machining by rapid prototyping method
Abstract
Introduction. This paper presents the results of obtaining a complex-profile tool electrode (TE) for copy-and-pierce electrical discharge machining by casting technology. This method consists in using a master model by rapid prototyping method. The purpose of the work: experimental study of accuracy assurance in manufacturing of complex-profile TE by casting with the use of rapid prototyping technology for copy-piercing electrical discharge machining. Research Methods. The master model of TE was produced on the Envisiontec Perfactory XEDE machine using stereolithography technology. Si500 photopolymer was used as a starting material. Intermediate and final surface deviation measurements were performed on a Contura Carl Zeiss G2 CMM. Calculation of the gutter and feed system was performed in ProCast software. A casting was obtained from casting brass LC40S (Cu-40 Zn-Pb). The study of the process of copy-piercing electrical discharge machining of TE made by casting with the use of rapid prototyping technology was carried out with the help of Smart CNC copy-piercing machine in the environment of transformer oil. Operating parameters: pulse turn-on time (Ton, μs), voltage (U, V), current (I, A). Results and discussion. The methodology of design and manufacturing of complex-profile TE with application of rapid prototyping technology for copy-piercing electrical discharge machining is developed. The analysis of shape deviation shows that errors occur during the manufacturing of the master model by stereolithography. An experimental study of the shape deviation of the master model shows surface concavity in the range of 0.03 to 0.07 mm depending on the arrangement of the sides. It is shown that the optimized master model has 25 % less shape deviation. A sprue-feeding system (SFS) is developed for the fabrication of TE by casting technology. When porosity is evaluated, it is found that pores are concentrated in the SFS and riser, which positively affects the quality of the casting. Manufacturing of the tool electrode with the help of casting technology showed that all accuracy and roughness parameters are within the specified tolerance and correspond to the initial drawing data. Experimental study of the process of electroerosion machining of the profile groove of the TE manufactured by casting on the investment casting model obtained with the use of rapid prototyping technology is carried out. It is established that the dimensions of the obtained groove meet the stated requirements.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):138-152
138-152
MATERIAL SCIENCE
A review of research on high-entropy alloys, its properties, methods of creation and application
Abstract
Introduction. The paper discusses the prospects for studying high-entropy alloys (HEA), metal materials with unique properties. The study of high-entropy alloys is an urgent area of research in connection with its properties, environmental sustainability, economic benefits and technological potential. HEA are of interest to researchers due to its stability, strength, corrosion resistance and other characteristics, which makes it promising for use in the aerospace industry, automotive, medicine and microelectronics. Thus, HEA research contributes to the development of new materials and technological progress, providing opportunities for creating innovative products and improving existing solutions. To effectively use the potential of high-entropy alloys, research is required in a number of areas. First, it is necessary to improve the production technology of such alloys and develop new methods for obtaining HEA with improved characteristics and reduced cost. Secondly, it is necessary to establish the basic principles of operation of high-entropy alloys and to study the mechanisms influencing its properties. It is also necessary to develop new alloys with specified properties and conduct experiments and computer simulations to optimize the characteristics of the alloys and determine the best compositions. The purpose of the work is to study developments in the field of high-entropy alloys and conduct a comparative analysis of published studies on improving the properties of high-entropy alloys. The research method is a review and analysis based on developments mainly for 2020-2024, which were carried out by domestic and foreign scientists. The paper discusses the prospects for the study of high-entropy alloys, materials with a wide range of applications in various industries. The paper presents the results of research, mainly for 2020-2024. The main properties of high-entropy alloys are described, such as high strength, corrosion resistance, fatigue properties, plasticity and deformability, thermal stability, electrical conductivity and magnetic properties, as well as the possibility of creating alloys with specified characteristics. The most common methods of changing the properties of alloys have been identified. The directions of further development of research in this area are considered. Results and discussion: a literature review shows that developments and research are carried out on all possible properties of HEA, but most of it is devoted to corrosion-resisting properties and thermal stability. Of the methods used in high-entropy alloys, the most common and universal can be considered the alloying of high-entropy alloys with other metals. Studies also confirm that alloying metals are selected depending on its characteristic properties. The number of scientific works also confirms the relevance of this topic and the need for its study. The authors noted that future studies on the fatigue properties of high-entropy alloys, as well as the properties of alloys under the influence of magnetic and electric fields are the most interesting.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):153-179
153-179
Analysis of changes in the microstructure of compression rings of an auxiliary marine engine
Abstract
Introduction. The cylinder-piston group (CPG) of a marine-type internal combustion engine is subjected to high operational loads. The reliability, durability and efficiency of the engine depend on the proper operation of the CPG. The change in the direction of piston movement and the lack of lubrication caused by the spraying of lubricant during operation, lead to increased wear of the moving package of piston rings. Having determined the factors influencing the changes in the structure of the metal during operation, it can be taken into account in the manufacturing technology and hardening of these parts. The subject of the study: the object of research is the used-out upper and lower compression rings of the cylinder-piston group of the HIMSEN 4H21/32 auxiliary marine engine. Purpose of the work is to consider the change in the structure and microstructure of the material of the compression piston rings of the HIMSEN 4H21/32 auxiliary marine engine arising as a result of operation; to compare the results of evaluating microstresses and deformations of the surface layer of parts by metallographic methods and X-ray diffraction analysis for various operating conditions of the upper and lower compression rings. Methods. Metallographic and X-ray methods were used in the study. The conditions of X-ray photography are described; X-ray diffraction analysis was carried out on a Dron-3M diffractometer. Residual microdeformations were determined, as well as the sizes of coherent scattering regions (D) and the density of dislocations on the surfaces of the samples. Results of the work. The results of metallographic and X-ray diffraction analysis (XRD) are presented. The residual macro- and microstresses and the sizes of the coherent scattering regions (D) of the surface layer of compression rings are determined. The results of X-ray diffraction analysis are comparable with the results of metallographic studies, and the convergence of the results is observed. Scope of the results application: the results of the study can be used in the selection of manufacturing technology for compression rings of marine internal combustion engines (MICE). Conclusions. It is advisable to evaluate changes in the manifestations of the stress state of cast iron under the influence of various factors. This will allow selecting the optimal technology for manufacturing compression rings to ensure the reliability of its operation. Ring quality control by various methods of structure assessment also makes it possible to predict the conditions of destruction of compression rings during operation. An increase in the degree of defectiveness of the upper ring occurs due to various kinds of deformations of the crystallites. As a result of inelastic deformations during ring operation, the resulting dislocations cause strong mechanical stresses.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):180-191
180-191
The effect of hot plastic deformation on the structure and properties of surface-modified layers after non-vacuum electron beam surfacing of a powder mixture of composition 10Cr-30B on steel 0.12 C-18 Cr-9 Ni-Ti
Abstract
Introduction. Currently, austenitic Ni-Cr steels are widely used in the oil and gas industry for drilling wells due to its high corrosion resistance, non-magnetic properties, high impact strength, ductility and weldability. However, in order to increase the service life of products, it is necessary to increase the abrasive resistance of the surface layers while maintaining chemical resistance, which is a difficult technological task. The solution to such a problem can be the creation of sheet blanks “austenitic Ni-Cr steel - modified layer” subjected to hot plastic deformation. The purpose of the work is to study the effect of hot plastic deformation on the structure and phase composition of “modified layer – base metal” compositions obtained by the method of non-vacuum electron beam surfacing of a powder mixture of boron and chromium on austenitic Ni-Cr steel 0.12 C-18 Cr-9 Ni-Ti. Material and methods of research. The work investigated specimens made of steel 0.12 C-18 Cr-9 Ni-Ti with a modified 10Cr-30B layer formed by non-vacuum electron beam surfacing of a powder mixture of chromium and boron, and subsequent hot plastic deformation at a temperature of 950 °C. The research methods are mechanical tests for microhardness, X-ray spectral analysis of the modified layer, metallographic studies, profile analysis, calculation of lattice parameters. Results and discussion. It is revealed that after deformation, defect-free compositions are obtained, the surface layer of which is a matrix composite material containing oriented chromium carbide particles with altered crystal lattice parameters. After plastic deformation, cracks and delamination are not recorded, which allows us to speak about the high quality of the “modified layer – base metal” compositions with increased hardness values exceeding 6.5 times as-delivered steel 0.12 C-18 Cr-9 Ni-Ti (3…11 GPa and 2 GPa, respectively). In the modified layer, complex borides of type (FexCry)B are formed and located in a γ-solid solution of iron. The lattice parameter decreases for γ-iron from 3.588 Å to 3.580 Å, for boride parameter a from 5.126 Å to 5.111 Å, parameter c from 4.228 Å to 4.199 Å.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):192-205
192-205
Structure of Inconel 625 alloy blanks obtained by electric arc surfacing and electron beam surfacing
Abstract
Introduction. Development of the manufacturing industry has led to the emergence of new methods for manufacturing blanks and parts. One of these new promising methods is additive manufacturing and, in particular, electric arc and electron beam surfacing technologies. The use of these technologies in the production of blanks from heat-resistant materials provides a number of significant advantages. The paper presents the results of a study of the microstructure of Inconel 625 specimens obtained using EBAM and WAAM technologies. The purpose of the work is a comparative analysis of the microstructure of Inconel 625 nickel alloy blanks obtained using EBAM and WAAM technologies. Methods and materials. The paper examined specimens obtained using EBAM and WAAM technologies. The specimens were manufactured using equipment developed at Tomsk Polytechnic University. Metallographic studies, scanning electron microscopy were carried out, and the microhardness of the obtained specimens was determined. Results and discussion. Comparison of specimens obtained by two different additive printing technologies EBAM and WAAM showed general patterns of structure formation that appear when using additive technologies. The specimens have a dendritic microstructure and contain zones rich in Ti, Mo and Nb, which is typical for nonequilibrium cooling. Pores are also observed in the specimens. The grains in the specimens have a predominantly elongated shape and are oriented in the direction of heat removal. The length of the grains reaches 1 mm. Differences in the specimens are observed in the number of formed inclusions of intermetallic compounds, in the number of formed pores, in the size of the grains. The EBAM technology provides more uniform structure. The difference in hardness between EBAM and WAAM is about 3.5 %. At the same time, the speed of specimen production using the WAAM technology is significantly higher.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):206-217
206-217
Study of surface hydrophilicity of metallic materials modified by ultraviolet laser radiation
Abstract
Introduction. Surface modification using laser radiation is a promising direction in the field of creating new technologies for treatment metal materials, including those for medical purposes. The ability of lasers to change the surface characteristics of a material and, consequently, its interaction with the environment has attracted great interest among researchers. Despite numerous recommendations for the use of laser surface treatment, there is still lack of systematic and detailed studies on the influence of parameters on the structural-phase state and properties of the modified surface, especially concerning ultraviolet laser exposure. The purpose of this work is to study the hydrophilicity of the surface of TiNi alloy and stainless steel after UV laser treatment. Materials and methods of the study: experimental samples made of TiNi (TN-10) alloy and 12KH18N9T (AISI 321) stainless steel were locally (beam diameter 0.5 cm) exposed to a solid-state Nd:YAG laser at the wavelength of 266 nm, with a pulse duration of ~ 5 ns, and pulse repetition rate of 10 Hz. The material was exposed to a constant output radiation energy density of 0.1 J/cm2, with a change in the exposure duration from 10 to 600 s. Before and after UV laser treatment, the wettability of the material surface and free surface energy were determined. The structure, elemental and phase composition, and surface topography of TiNi and steel were studied using scanning electron microscopy with the determination of the elemental composition by energy-dispersive spectroscopy, X-ray phase analysis, and profilometry. Results and discussion. Ultraviolet laser treatment of the surface of TiNi alloy and steel samples leads to an increase in their hydrophilicity. In the initial state, the contact angle of wetting is ≈75° for both materials, and after ultraviolet laser treatment it decreases to ≈11-13° for TiNi and to ≈22° for steel. The phase composition of steel does not change during laser treatment, and phases belonging to oxides are recorded on the surface of TiNi after 420 seconds of treatment. Ultraviolet laser treatment of TiNi alloy and steel leads to an increase in free surface energy, a change in the ratio of its components (a decrease in the dispersed component and a significant increase in the polar component), an increase in the oxygen content on the surface of both materials. With long laser exposure times (more than 300 seconds), microcracking occurs on the surface of the processed material, leading to an increase in roughness. The change in the surface topography (roughness) of TiNi alloy does not have a noticeable effect on the wettability of the surface of metal materials, and for steel samples, there is an insignificant tendency to reduce the contact wetting angle with increasing roughness. The degree of hydrophilicity of metal materials, characterized by the contact wetting angle, increases with an increase in the duration of laser exposure due to saturation of the surface with free oxygen and an increase in free surface energy (its polar component). Based on the studies, it can be concluded that ultraviolet laser treatment is an effective way to change the wettability of metal materials.
Obrabotka Metallov / Metal Working and Material Science. 2024;26(4):218-233
218-233