Ultrasonic Finishing Research Articles

Post-Production Finishing Processes Utilized in 3D Printing Technologies

Additive manufacturing (AM) has revolutionized production across industries, yet challenges persist in achieving optimal part quality. This paper studies the enhancement of post-processing techniques to elevate the overall quality of AM-produced components. This study focuses on optimizing various post-processing methodologies to address prevalent issues such as surface roughness, dimensional accuracy, and material properties. Through an extensive review, this article identifies and evaluates a spectrum of post-processing methods, encompassing thermal, chemical, and mechanical treatments. Special attention is given to their effects on different types of additive manufacturing technologies, including selective laser sintering (SLS), fused deposition modeling (FDM), and stereolithography (SLA) and their dedicated raw materials. The findings highlight the significance of tailored post-processing approaches in mitigating inherent defects, optimizing surface finish, and enhancing mechanical properties. Additionally, this study proposes novel post-processing procedures to achieve superior quality while minimizing fabrication time and infrastructure and material costs. The integration of post-processing techniques such as cleaning, surface finishing, heat treatment, support structure removal, surface coating, electropolishing, ultrasonic finishing, and hot isostatic pressing (HIP), as steps directly within the additive manufacturing workflow can immensely contribute toward this direction. The outcomes displayed in this article not only make a valuable contribution to the progression of knowledge regarding post-processing methods but also offer practical implications for manufacturers and researchers who are interested in improving the quality standards of additive manufacturing processes.

Finite Element Analysis of the Stress–Strain State of the Deformation Zone of a Workpiece from UFG Grade 4 Ti Subjected to Abrasive-Free Ultrasonic Finishing

Finite Element Analysis of the Stress–Strain State of the Deformation Zone of a Workpiece from UFG Grade 4 Ti Subjected to Abrasive-Free Ultrasonic Finishing

Finite element analysis of stress-strain state of the deformation zone of a UFG TI Grade 4 workpiece subjected to abrasive-free ultrasonic finishing

An effective approach to increasing the fatigue resistance of metal products is to create compressive residual stresses on the surface of the product using surface plastic deformation (SPD) processing. One of the effective SPD methods is the process of abrasive-free ultrasonic finishing (AFUF). Another well-known approach to improving mechanical properties including fatigue resistance is to create an ultrafinegrained (UFG) structural state in the product. This research focuses on the finite-element study of the stress-strain state of a UFG workpiece subjected to SPD by the AFUF method. Commercially pure Grade 4 titanium in the UFG state obtained by the ECAP-Conform method was chosen as a workpiece material. In the course of the study, the stress-strain state of the deformation zone was analyzed after a single indentation with subsequent unloading under the elastic-plastic scenario. The effect of the indenter oscillation amplitude and its geometry on radial residual stresses including their depth of occurrence, average normal stress and strain intensity was analyzed. It was found that as the indenter radius increases, the strain intensity (e) value decreases. The e parameter distribution has a gradient nature with a decrease in values from the surface to the center of the workpiece. An analysis of simulation results shows that radial residual stresses in the deformation zone are predominantly compressive, and, accordingly, they will increase the fatigue resistance of the finished product. It was established that as the indenter oscillation amplitude increases, the values of compressive radial residual stresses also increase. Their maximum values reach 540 MPa at an amplitude of 75 μm with the depth of these stresses up to 0.3 mm. An increase in the indenter radius, i.e. in fact the contact area, leads to an increase in the magnitude of compressive radial residual stresses with an almost linear behavior.

INCREASING THE DURABILITY OF CENTRIFUGAL PUMP SHAFTS BY COMBINED METHODS

The article analyzes the literature, which showed that in recent years there have been new technological methods of strengthening the surface layers of the centrifugal pumps shafts necks. They are based on the use of environmentally friendly method of electrospark alloying (ESA) (cementation, application of combined coatings with molybdenum disulfide (MoS2), coatings of Al-C-B) and without comparative tests for wear resistance is difficult to prefer one method or another. Studies on the friction machine СМЦ -2 found that the weight wear of round specimens of polished steel 40X, in contact with lubrication of turbine oil T-22 with babbitt inserts of the sliding bearing according to the scheme "disk-insert", 1.15 times greater than steel 30X13 and, respectively, 2.50 and 4.41 times than 40X steel after cementation by ESA (CESA) + non-abrasive ultrasonic finishing (NAUF) and ESA (Mo + S) + NAUF. In turn, the linear wear of polished steel 40X round samples is greater than steel 30X13 1.09 times and, respectively, 2.83 and 5.85 times than steel 40X after CESA + NAUF and ESA (Mo + S) + NAUF. The lowest coefficient of friction was recognized as 0.025 and 0.030, which belongs to the coating of MoS2, formed, respectively, on samples of steel 30X13 and 40X and treated with NAUF.
 Analysis of the linear wear change nature of steel 40X and 30X13 round samples, both hardened and not hardened, showed that all samples first have more intense wear, which after 2 hours of abrasion slows down, becomes more stable and at first glance resembles exponential dependence. Samples reinforced in the sequence ESA (Mo + S) + NAUF have the best wear resistance, the wear of which after 8 h of tests is 0.9 and 1.1 μm, respectively, of steel 30X13 and 40X.
 Weight and linear wear of 40X steel specimens without hardening is higher compared to non-reinforced 30X13 steel specimens tested in pair with BK8 counterbody under conditions of abundant lubrication with I40A industrial oil, by 21.7 and 14.2%, respectively; in comparison with samples of 40X steel with a coating applied by the method of ESA composition (Al-C-B) followed by NAUF, respectively, 77.8 and 84.7%; and 30X13 steel with similar treatment of ESA (Al-C-B) + NAUF, 98.0 and 71.8%, respectively.

Rational modes of surface smoothing using ultrasonic finishing

The rational parameters of the regime of surface plastic deformation (burnishing) with simultaneous exposure of ultrasonic vibrations are experimentally determined: an initial depth of penetration of the indenter, an angular and linear speeds of the workpiece. It has been established that under ultrasonic treatment the microhardness of the surface increases, with intensive ultrasonic treatment the microhardness increases to 7200 MPa, but at the same time chips are observed on the surface. Keywords: wear resistance, restoration of parts, burnishing, ultrasonic processing, non-abrasive processing, surface plastic deformation, processing mode. kharchenko.mv@bk.ru

Electric-Spark Alloying of Metal Surfaces with Graphite

The article reviews and analyses the current scientific research in the field of surface treatment of metal surfaces with concentrated energy fluxes (CEF) — the electric-spark (in the literature, known also as electrospark) alloying (ESA), which makes it possible to obtain surface structures with unique physical, mechanical and tribological properties at the nanoscale. The ESA method with a graphite electrode (electrospark carburizing — EC) is based on the process of diffusion (saturation of the surface layer of a part with carbon), and it is not accompanied by an increase in the size of the part. In this article, the influence of the EC parameters on the quality of the carburized layer is investigated. The microstructural analysis shows that the three characteristic zones could be distinguished in the structure: the carburized (‘white’) layer, the finely dispersed transition zone with fine grain, and the base metal zone. The analysis of the results of the durometric studies of the coatings is carried out. To achieve the required parameters of dimensional accuracy and roughness of the working surface of the part after the EC process, it is necessary to use the method of non-abrasive ultrasonic finishing (NAUF). In addition, because of applying the NAUF method, the surface roughness is decreased, the tensile stresses are changed to the compressive ones, and the fatigue strength is increased too. In addition, to reduce the roughness of the treated surface, it is proposed to apply the EC technology in stages, reducing the energy of the spark discharge at each subsequent stage. In order to increase the quality of the carburized layer obtained by the EC process, it is proposed to use a graphite powder, which is applied to the treated surface before alloying. The comparative analysis shows that, after the traditional EC process at Wp = 4.6 J, the surface roughness of steel 20 is Ra = 8.3–9.0 μm, and after the proposed technology, Ra = 3.2–4.8 μm. In this case, the continuity of the alloyed layer increases up to 100%; there increases the depth of the diffusion zone of carbon up to 80 μm as well as the microhardness of the ‘white’ layer and its thickness, which increase up to 9932 MPa and up to 230 μm, respectively. The local micro-x-ray spectral analysis of the obtained coatings shows that, at the EC process carried out in a traditional way, the applying Wp = 0.9, 2.6, 4.6 J provides the formation of the surface layers with high-carbon content depths of 70, 100, 120 μm, respectively, and with the use of a graphite powder, they are of 80, 120, 170 μm. While deepening, the amount of carbon is decreasing from 0.72–0.86% to the carbon content in the base metal — 0.17–0.24%. In the near-surface layer formed with the use of the new technology, the pores are filled with free graphite, which could be used as a solid lubricant to improve the operating characteristics of the friction-pairs parts processed thereby.

Шероховатость и микротвердость ультрамелкозернистого титана Grade 4, подвергнутого безабразивной ультразвуковой финишной обработке

Increasing the fatigue resistance of implants is an important scientific and technical problem. One of the solutions to this problem is the high-strength state formation due to the ultrafine-grained (UFG) structure. However, high-strength alloys are characterized by greater sensitivity to stress concentrators and the surface roughness parameter. In turn, implant designs, as a rule, imply the presence of concentrators in the form of various grooves, threaded elements, etc., and the manufacturing technology supposes mechanical processing with an ambiguous effect on a finished product surface. The application of additional surface finishing, for example, abrasive-free ultrasonic finishing (AFUF), is a solution to this problem. This work aims to study the effect of different AFUF modes on the microhardness and roughness of a cylindrical blank made of Grade 4 commercially pure titanium in the UFG state. During the study, the authors assessed the effect of the rotation frequency of a workpiece and the static force of pressing the tool against the processed workpiece on the surface parameters; carried out microstructural studies of the obtained samples. The results showed that processing titanium in the UFG state by the AFUF method leads to a significant increase in the surface microhardness and a decrease in its roughness. For example, depending on the mode, the increase in microhardness can reach from 2 to 3.5 times. The authors investigated the effect of a power level of ultrasonic treatment on roughness and microhardness and considered various variants of surface pretreatment. The study identified that an increase in the speed of rotation of a workpiece reduces the roughness of a machined workpiece, while the microhardness increases.

The Influence of Surface Hardening by Combined Thermo-Forced Impacts on the Fatigue Life and Damage of the VT22 Titanium Alloy

The influence of electromechanical surface treatment (EMT) and nonabrasive ultrasonic finishing (NAUF) on the titanium alloy and the complex influence of the above treatment methods and subsequent aging on the fatigue life and the change in the surface microhardness is studied. Specimens for research are made of rods manufactured of the transition VT22 alloy after the standard thermomechanical treatment. The EMT is conducted by rolling the surface of the specimen with a roller pressed to it and passing a high-density current between them. As a result, the surface thermomechanical treatment is conducted under fast local heating and cooling of the surface. The NAUF is performed by shock treatment with a striking ultrasonic emitter on the treated surface. The rotational bending loading of specimens at stress amplitude of 0.5σu upon the NAUF results in an increase in fatigue life by a factor of 1.8 in comparison with the untreated initial state, accompanied by a slight increase in the microhardness of up to 16%. The EMT reduces microhardness by almost 20% and fatigue life by 70%. The combined processing by EMT + NAUF insignificantly affects microhardness, but increases the life by 40% compared with the EMT. Aging at a temperature of 450°C for 5 h increases the microhardness upon the EMT by 30–40% with a simultaneous twofold increase in durability. The aging of the specimens subjected to EMT + NAUF practically does not increase microhardness, but it increases durability by almost three times compared with the EMT. A fractographic analysis of the fracture surface has shown that the reduction in the life after EMT is associated with a reduction in the stage of crack initiation, which virtually excludes this stage of accumulation of fatigue damage from the overall durability of the specimen.

Influence of surface hardening by combined thermal force impacts on VT22 titanium alloy fatigue life and damage

The study covers the influence of electromechanical surface treatment (EMT), non-abrasive ultrasonic finishing (NAUF), their complex influence with subsequent aging on the fatigue life and surface microhardness changes. Samples for research were made of VT22 transition alloy rods after standard thermomechanical treatment. EMT was carried out by sample surface rolling with a roller and applying a high density current between them. As a result, surface thermomechanical treatment was carried out with the local fast surface heating and cooling. NAUF were implemented by shock treatment with an ultrasonic emitter striking on the treated surface. This revealed 1.8 times higher fatigue life when loading by rotational bending (with amplitude of 0.5σв) for samples after NAUF in comparison with the untreated initial state together with a slight increase in microhardness (up to 16 %). EMT reduces microhardness and fatigue life by almost 20 % and 70 %, respectively. EMT + NAUF complex processing has an insignificant effect on microhardness, but it increases fatigue life by 40 % with respect to EMT. Aging at 450 °C for 5 hours increases microhardness after EMT by 30–40 % with a simultaneous increase in fatigue life by 2 times. The aging of samples subjected to EMT + NAUF revealed virtually no increase in microhardness, but increased fatigue life by almost 3 times (as compared to EMT). According to fractography results, the reduction in fatigue life after EMT is associated with a reduction in the crack initiation stage, which virtually excludes this stage of fatigue damage accumulation from the overall sample fatigue life.

Influence of parameters of ultrasonic finishing on the roughness of machined surfaces of parts made of tool steels

The influence of the parameters of plastic deformation by ultrasonic burnishing during finishing treatment on the surface roughness of workpieces made of Р6М5 and 9ХС steels with an initial surface hardness of 57¸60 HRC is investigated. The D-optimal Hartley—Kono plan was used in the experiments for four factors (workpiece rotation frequency, feed, loading force, ultrasound power). Keywords: ultrasonic finishing, indenter, ultrasound power, surface roughness, plastic deformation zone. v.slutskov@narfu.ru

ОБРАБОТКА ЭЛЕКТРОИСКРОВЫХ ПОКРЫТИЙ МЕТОДОМ УЛЬТРАЗВУКОВОГО ПЛАСТИЧЕСКОГО ДЕФОРМИРОВАНИЯ

In the paper there are shown results on roughness parameter decrease on the electrospark coatings of 20H13 and 30 steel surfaces by means of smoothing with the use of the plant for non-abrasive ultrasonic finishing (NUF). 
 For the coating formation there were used Ni, Cu and an intermetallic alloy based on Ni3Al phase. At the NUF increase of coatings formed with the use of Cu there is a roughness growth caused with material “pickup” upon an indenter. It is determined that for smoothing the surfaces with electrospark coating with the assurance of roughness considerable decrease a six-fold NUF processing is required. A microstructure of the coating obtained with the use of anode material based on the Ni3Al alloy consists of columnar crystal grains the cross-section dimensions of which change from some mkm to several tens of nm. Crystal grains are directed mainly normally regarding a cathode surface. By means of micro-X-ray spectrum analysis there is defined an elementary composition of columnar crystal grains corresponding to the alloy of the Nix-Aly-Fez system which is alloyed with Cr and contains admixtures of Si and Mn. By means of the microstructure investigation of the coating smoothed surface in a number of areas there are revealed crystal grains with the signs of plastic deformation.

Kinematics of ultrasonic processing

The paper considers the kinematics of ultrasonic finishing processing with implementing the vibrations tangentially to the surface machined. The investigations are conducted on determining the main kinematic parameters of the method mentioned and their influence on the character of the tool trace on the machined part surface. The mathematical description of the motion trajectory of the deforming tool on the processed surface is presented. Its analysis allows us to find out the main principles of the formed trajectories and their relative location as well as the possibilities of increasing the processing efficiency.

Searching for a rational schedule of a burnishing process with superimposition of ultrasonic vibrations

An ultrasonic finishing treatment unit was used for experimental researches to find effective burnishing modes. Based on the research findings of an obtained surfaces microtopography the following parameters were determined: Ra – arithmetical mean deviation of the profile and Pc – average number of profile end points per 1 cm of the surface length, by which the quality of treatment was evaluated.

Sparsest packing of two-dimensional objects

The concept of the sparsest packing is introduced in this paper. The sparsest packing is aimed to place the objects in the container as distant as possible. More specifically, the minimal Euclidean distance between the objects, as well as, between the objects and the boundary of the container is maximised. This new problem statement is motivated by modern clean and energy-saving technologies such as ultrasonic hardening and finishing by detonating gas mixtures. The sparsest packing of two-dimensional objects in a circular container is considered subject to balancing conditions. The objects may have regular or irregular shapes bounded by arcs and line segments. Using the phi-function technique a mathematical model is formulated and a corresponding nonlinear programming problem is stated. A solution algorithm is proposed and computational results are presented to illustrate the approach.

Influence of structure and properties of surface layer on fatigue durability of hardened steels strengthened by combined electromechanical treatment

Using the example of hardened carbon steels (steel 45, U8), the effect of combination of various surface hardening technologies is considered (using electromechanical processing, surface plastic deformation, non-abrasive ultrasonic finishing and their combination) on changes in structural state and surface microhardness, cyclic durability of hardened specimens and fatigue failure mechanisms. The studies were carried out by the methods of optical and scanning electron microscopy and by microhardness and fatigue tests. It is shown that for the investigated steels in quenched state, a high-speed pulsed thermo-deformation effect during electromechanical processing is accompanied by an increase in the surface microhardness (by more than 50 %) and decrease in the fatigue limit (by 20 – 30 %). Such a change in properties is associated with formation in the surface layer of substantially non-equilibrium, inhomogeneous in chemical composition, ultradispersed phases with increased hardness. At the same time, in the near-surface metal volumes tempering processes of the hardened structure proceed with the formation of softening zones and tensile residual stresses, accompanied by a decrease in the microhardness in these zones and the fatigue limit of the specimens. Such effects reduce some of the materials performance characteristics during surface hardening. The ways to improve the properties of such products due to additional technological operations require further studies. Combined surface hardening (based on electromechanical processing, surface plastic deformation and non-abrasive ultrasonic finishing) of carbon steels allows, due to variations in the intensity of temperature and deformation effects, to purposefully change the structural-phase composition and stress-strain state of the surface and near-surface metal layers. As a result, it becomes possible to form a balanced complex of strength and fatigue characteristics of the samples, depending on the preliminary heat treatment of steel. The operations of surface plastic deformation and non-abrasive ultrasonic finishing after electromechanical hardening, due to intensive plastic deformation provide smoothing of the surface and healing of near-surface defects and allow correction of stress-strain state of the processed metal. It provides an increase in microhardness in the tempering zone by 20 – 25 % and the fatigue limit of the samples by 25 – 30 %.

Influence of the Surface Structure and Properties on the Fatigue Strength of Electromechanically Strengthened Quenched Steel

Abstract—For the example of quenched carbon steel 45 and U8 steel, the influence of surface hardening (electromechanical treatment, surface plastic deformation, nonabrasive ultrasonic finishing, and various combinations) on the surface structure and microhardness, the cyclic durability of the hardened samples, and the mechanisms of fatigue failure is analyzed. Research by means of optical and scanning electron microscopy, microhardness measurement, and fatigue tests shows that, for the quenched carbon steels, high-speed pulsed thermal deformation in the course of electromechanical treatment increases the surface microhardness (by more than 50%) and decreases the fatigue limit (by 20–30%). That is associated with the formation of hard nonequilibrium ultradisperse phases of nonuniform chemical composition in the surface layer. The quenched structure close to the surface is tempered, with the formation of softening zones and the appearance of residual tensile stress. Accordingly, the microhardness in these zones declines and the fatigue limit falls. Such decrease in performance of the steel on surface hardening merits further study, along with potential technologies for improving its performance. Surface hardening of carbon steels by some combination of electromechanical treatment, surface plastic deformation, and nonabrasive ultrasonic finishing permits adjustment of the structure and phase composition and the stress–strain state of surface and subsurface layers of the steel by varying the temperature and deformation. By that means, balanced strength and fatigue characteristics of the samples may potentially be obtained by appropriate preliminary heat treatment. Intense surface plastic deformation and nonabrasive ultrasonic finishing after electromechanical hardening may be used to smooth the surface, mend subsurface defects, and correct the stress–strain state of the steel. That increases the microhardness in the tempering zone by 20–25% and the fatigue limit of the samples by 25–30%.

Influence of Ultrasonic Finishing on the Surface Roughness of Ship Components

The influence of plastic deformation by ultrasonic smoothing on the surface roughness of 17Kh18N9 and 20Kh1M1F1TR steel billet in finishing is studied. In the experiments, a D-optimal Hartley–Kono design for four factors is employed. The four factors are the speed of billet rotation, the supply, the clamping force, and the ultrasonic power.

Development of Fatigue Damages in a Pseudo-α-Titanium Alloy after Intense Thermomechanical Treatment

The influence of surface hardening by electrochemical treatment, abrasive-free ultrasonic finishing treatment, and their combination on the accumulation of fatigue damages in a pseudo-α-titanium alloy (PT3V) during pulsed cyclic loading in a transition stage of fatigue (104–105 cycles) is studied. The fatigue damage accumulation kinetics is estimated using the inelasticity parameters of a specimen (hysteresis loop width, cyclic creep, rigidity (compliance)) during cyclic loading, an analysis of fracture surfaces, and the crack growth rate. The state of surface layer is shown to play a key role in the change in the fatigue life of laboratory specimens. The type of surface hardening only weakly affects the accumulation of fatigue damages at the stages of stable crack growth and rupture.

Tribological Properties of Brass Surfaces Machined by Abrasive - Free Ultrasonic Finishing Process

Brass mechanical properties are not ideal, particularly when the brass is exposed to the effects of mechanical wear. Final finishing of functional surface of machine component is substantial for the particular choice of brass. The aim of the research was to approve or disapprove the hypothesis if abrasive - free ultrasonic finishing (bufo) of brass has higher wear resistance of surface compared to the classical machining. The results of the experiment showed that abrasive - free ultrasonic finishing (bufo) has a major impact on the size of the elliptical wear area. Surface finishing by classic machining formed on average a 41% larger elliptical wear area compared to surface with abrasive - free ultrasonic finishing. The hypothesis of experiment were verified and it is possible to consider that abrasive - free ultrasonic finishing (bufo) has considerable influence on wear resistance of the surface of machine parts.

RESEARCH OF MICRORELIEF AND STRUCTURE OF THE SURFACE LAYER BY LASER AND ULTRASONIC THERMO-STRAINING TREATMENT OF TOOL STEEL

In this article, to improve the microrelief and structure of the surface layer of tool steel by combined method of the laser heat hardening and subsequent ultrasonic strain hardening and finishing was suggested. The results of experimental studies the formation of the microrelief on the surface, as well as the patterns of changes in the structure and microhardness of the surface layer of tool steel W8 using a CO2 laser and one-pin ultrasonic tip, are presented. The influence of technological regimes of the laser heat treatment (power of a laser beam and feed rate) on the structure, microhardness and size of the heat affected zone were established. It is shown that the microhardness of the surface layers increased more than 3.5 times at the laser heat treatment and at the ultrasonic strain treatment by 30...40% in comparison with the initial state. Using the combined method of thermo-strain hardening and finishing provided improving in 2 times in the surface roughness and increasing in 4.5 times of the surface layer microhardness as compared with untreated surface. It will allow increasing the wear resistance of the working surfaces of tools.