Electron-beam Additive Technology Research Articles

Macro- and Microstructural Homogeneity of Nickel-Based Superalloy Product Material Obtained by Wire-Feed Electron Beam Additive Manufacturing

This paper investigates the structural homogeneity of samples of articles made of ZhS6U alloy obtained by wire-feed electron beam additive technology. It is found that the formed material is represented by directionally growing dendrites and does not contain any defects. The temperature gradient value and its dependence on the height of the additively formed product are estimated using the change in the primary dendrite arm spacing. On this basis, it is concluded that the temperature gradient values achieved during the additional formation process correspond to the modern methods of directional solidification. The features of the electron-beam additive process that affect the heat removal conditions and cause changes in the temperature gradient are shown. It is found that changes in these conditions do not significantly affect the size and morphology of the intermetallic γ'-phase. It is demonstrated that the mechanical properties of the additively formed product material are superior to those of the original material in the as-cast state.

Исследование свойств сплавов на основе кремниевой бронзы, напечатанных с применением технологии электронно-лучевого аддитивного производства

Introduction. Additive technologies make it possible to curb material expenses by reducing allowances for the final dimensional machining of workpieces. For such expensive materials as copper and copper alloys, this method is considerably attractive from a perspective of increasing resource efficiency in production. The operational properties of the C65500 alloy manufactured using additive technologies have not been fully studied and require additional research. The aim of the work is to study the structural and phase state, mechanical and operational properties of C65500 bronze specimens printed using electron beam additive manufacturing technology. In the work, specimens made of C65500 wire with different heat input values are studied, some of which were subjected to thermal treatment and mechanical processing, as well as specimens, manufactured using multi-wire technology. The work uses such research methods as the study of corrosion resistance of bronze specimens using a potentiostat, confocal laser scanning microscopy, friction tests and X-ray phase analysis. Results and discussion. Processing of specimens by plastic deformation (compression) and subsequent annealing leads to the most serious structural changes. Based on X-ray phase analysis, it is found that higher silicon content is observed in the case of the addition of silumins to bronze. The study of mechanical properties shows that the specimens, printed using multi-wire technology, have the highest strength properties. During tribological testing, fluctuations in the value of the friction coefficient are revealed, due to the scheme of the experiment and the combined adhesive-oxidative mechanism of specimens’ wear. The addition of 10 wt.% aluminum filament to bronze in the additive manufacturing process is an effective means for increasing the resistance of the material to electrochemical corrosion and increasing its wear resistance.

The Microstructural and Phase Evolution of the 3D Printed Ti–6Al–4V Alloy during Mechanical Loading

This paper presents the results of an in situ study on the evolution of the microstructure and phase composition of 3D-printed Ti–6Al–4V samples under tension in the transmission electron microscope col-umn. The microstructure of Ti–6Al–4V specimens manufactured by wire-feed electron beam additive tech-nology is shown to consist of columnar primary β-grains inside of which are α/α'-Ti laths separated by layers of the residual β-phase and gathered into packets. A characteristic feature of 3D-printed Ti–6Al–4V samples is the concentration nonuniformity of the alloying elements due to the partial decomposition of the marten-sitic α'-phase. The reorientation of the α/α'-Ti lattice near interfaces takes place during uniaxial tension. Deformation-induced α'→α" transformations can develop in the reoriented regions of the α/α'-Ti lattice, in places enriched in vanadium.

INFLUENCE OF THE GRADIENT ZONE EXTENT OF THE FUNCTIONAL GRADIENT PRODUCT OF THE CU/AL SYSTEM ON THE STRUCTURAL-PHASE STATE AND MECHANICAL PROPERTIES

The formation of functional gradient Cu/Al materials with a continuous intermetallic surface layer by electron beam additive manufacturing is associated with the formation of a number of inhomogeneities and defects in the structure. The main obstacles to obtaining stable and defect-free FGM structures on the surface of the copper base are the difference in the coefficients of thermal expansion of copper and aluminum at the boundary with the formation of intermediates, cracks and delaminations. The formation of a smooth gradient from copper to intermetallic Cu/Al layers allows to avoid the formation of cracks and delaminations. In the work, defect-free functional gradient Cu/Al materials with different gradient zone widths were obtained using electron beam additive technology. The structural-phase state and mechanical properties of FGM Cu/Al over the entire height of the printed material are investigated. It is established that the Cu/Al gradient zone of FGM consists of the phases α-Cu, Cu4Al, Cu3Al and Cu9Al4. It is established that the width of the gradient zone affects the volume fraction of CuxAly intermetallic phases, which, in turn, determine the magnitude of the elongation at a constant value of the tensile strength (305 ± 10 MPa). The microhardness values increase sharply in the gradient zone and have an uneven distribution due to the formation of Cu4Al, Cu3Al and Cu9Al4 intermetallides. It is shown that the upper part of the Cu/Al FGM, consisting of 67 % Cu and 33 % Al (vol.), demonstrates a sharp drop in mechanical properties, which is probably due to the formation of the Cu9Al4 phase, the volume fraction of which prevails compared to other intermetallic phases of the CuxAly system.

Structure and Mechanical Properties of Cu–Al–Mn Alloys Fabricated by Electron Beam Additive Manufacturing

In this work, the method of electron beam additive manufacturing (EBAM) was used to fabricate a Cu-based alloy possessing a shape memory effect. Electron beam additive technology is especially relevant for copper and its alloys since the process is carried out in a vacuum, which makes it possible to circumvent oxidation. The main purpose of the study was to establish the influence of the printing parameters on the structure of the obtained products, their phase composition, mechanical properties, dry friction behavior, and the structure-phase gradient that formed in Cu-Al-Mn alloy samples during electron beam layer-by-layer printing. The results of the study allowed us to reveal that the structure-phase composition, the mechanical properties, and the tribological performance of the fabricated material are mainly affected by the magnitude of heat input during electron beam additive printing of Cu-Al-Mn alloy. High heat input values led to the formation of the β1' + α decomposed structure. Low heat input values enabled the suppression of decomposition and the formation of an ordered 1 structure. The microhardness values were distributed on a gradient from 2.0 to 2.75 GPa. Fabricated samples demonstrated different behaviors in friction and wear depending on their composition and structure, with the value of the friction coefficient lying in the range between 0.1 and 0.175.

Features of the Macro-, Micro-, and Fine Structure of the Nickel Superalloy Product Material Formed by the Method of Electron Beam Additive Manufacturing.

In the present work, the products in the form of vertical walls were made of heat-resistant nickel-based superalloy ZhS32 via the method of electron beam additive technology. Unidirectional printing strategy was applied. The effect of heat input and 3D printing strategy on the macrostructure, dimensions, and morphology of microstructure elements was established. It was shown that the additive product material has a directed macrostructure. The only exclusion was the final layer with a thickness of no more than 3.5 mm. The directed macrostructure consisted of dendrites oriented predominantly along the crystallographic direction {001} of the primary dendrite arms. The misorientation of the dendrite axes did not exceed 9 degrees. The angle between the predominant dendrite growth direction and the normal to the substrate was 23 degrees. The average primary dendrite arms' spacing increased monotonically from 16 µm at 5 mm from the substrate to 23 µm in the final layers of the product material (the overall height was 41 mm). It was found that the average size of γ' (Ni3Al)-phase precipitations in the form of nanoscale and submicrocrystalline cuboids varied in the range of 76 to 163 nm depending on the distance from the substrate. The size of γ'-phase precipitations reached a maximum at about 30 mm from the substrate, while in the final layers of the product material, the average cuboid size did not exceed 135 nm. Extreme dependence of the size of γ'-phase precipitations on the height of the product followed from a combination of a given monotonic decrease in heat input and heat accumulation in the product material as it formed, as did additional heat removal by means of radiation during formation of the final layer of the product without re-melting. Chemical elements of the austenitic steel substrate material were not detected in the product material more than 8 mm from the substrate. There were no macrodefects, such as voids, in the entire volume of the product material.

Obtaining a steel-based metal matrix composite by wire-feed additive electron beam manufacturing with the introduction of tungsten powder

Wire-feed electron-beam additive technology is used to produce samples of a composite material based on the 40Cr9Si2 steel by additionally introducing tungsten powder during printing. Controlling the feed of wire and powder makes it possible to form composite structures in the surface layers of the samples while maintaining the sample bulks with high strength and plasticity. The content of tungsten in the surface layer increases smoothly. This has a positive effect on the structure of the samples and prevents cracking or delamination at the boundary between the base metal and the surface layer. The tensile strength of the layers decreases with the introduction of tungsten in comparison with the bulk of the sample. In this case, the surface layers are characterized by a multiple increase in wear resistance, especially at elevated test temperatures.

Phase Formation, Microstructure, and Mechanical Properties of Ni-Cu Bimetallic Materials Produced by Electron Beam Additive Manufacturing

The paper presents the results of applying wire-feed electron beam additive manufacturing technology to produce bimetallic samples of CuCr1 copper alloy and Udimet 500 nickel-based superalloy. Different printing strategies were used to obtain samples with a defect-free structure and high mechanical properties in the transition zone, not inferior to the strength of copper alloy. Two types of samples were fabricated with a sharp and smooth CuCr1/Udimet 500 interface. The printing strategies of type I and II samples differed in the combination and arrangement of nickel and copper alloy layers. Structural studies in the transition zone revealed mechanical mixtures of initial copper and nickel alloy components and solid solutions based on nickel, copper, and chromium. Despite the presence of defects and structural heterogeneities in the experimental samples, the mechanical properties of the main components are at a high level, corresponding to the typical properties of copper and nickel alloys. The strength of the transition zone in type II samples is between the strength of Udimet 500 and CuCr1.

Hardening mechanisms in stainless steel/aluminum bronze composite fabricated using electron beam additive manufacturing

The authors investigated the features of structural-phase state of a composite based on stainless austenitic steel with addition of 25 % (vol.) aluminum bronze. The composite was obtained by electron beam additive technology with simultaneous feeding of two wires. The paper considers analysis of the structural-phase state and mechanical characteristics. The contributions of various mechanisms to the composite hardening were evaluated. It was established that a multiphase structure is formed in the steel – 25 % bronze composite, which consists of 43.9 % austenite, 32.0 % ferrite and 24.2 % bronze. Dispersion-hardened copper particles are isolated in austenite grains, volume fraction of which counts 47 %. Dispersion-hardened NiAl particles with a volume fraction of 20 % are isolated in ferrite grains. Transmission electron microscopy data indicate a coherent conjugation of arrays of dispersion-hardened particles with the matrix. Such a composite structure provides an increase in the tensile strength by an average of 50 % compared to austenitic steel obtained by electron beam additive technology without the addition of aluminum bronze. It was found that the contributions of various hardening mechanisms to yield strength of austenite, ferrite and bronze amounted to 959.3, 972.7 and 408.7 MPa, respectively. Bronze grains do not make a significant contribution to increase in yield strength of the composite, except for its increase due to dislocation hardening. The main contributions to increase in the composite yield strength are made by austenite grains due to grain-boundary, dispersion and dislocation hardening and by ferrite grains due to grain-boundary, solid-solution and dislocation hardening.

Assessment of Structure and Properties Homogeneity after Repairing of a Nickel-Based Superalloy Product by the Electron Beam Additive Technology

Repairing damaged products made of nickel-based superalloys is an urgent task because replacing them with new products is a costly and time-consuming process. The present work considers the method of electron-beam additive manufacturing as an approach to the repair process. First of all, the initial product was produced by layer-by-layer deposition. Hereon, a part of the surface was removed, and then several more layers were deposited. Thus, three areas were considered in the work: initial, transitional, and repaired areas. Each of the formed regions was defect-free. It was found that the transition region was difficult to identify since it did not differ in structural-phase composition from the initial and repaired regions. It is shown that the complex thermal history consisting of periodic thermal exposure and repeated melting of the newly crystallized layers does not lead to the formation of defects and undesirable phases. Moreover, in all three regions, there is a redistribution of the chemical element content of the γ′ and γ phases towards an increase in the mismatch of their lattice parameters. The mechanical properties of the transition and repaired regions are not significantly different from the initial area.

Hardening Mechanisms in Stainless Steel/Aluminum Bronze Composite Fabricated Using Electron Beam Additive Manufacturing

The authors investigated the features of structural-phase state of a composite based on stainless austenitic steel with addition of 25% (vol.) aluminum bronze. The composite was obtained by electron beam additive technology with simultaneous feeding of two wires. The paper considers analysis of the structural-phase state and mechanical characteristics. The contributions of various mechanisms to the composite hardening were evaluated. It was established that a multiphase structure is formed in the steel–25% bronze composite, which consists of 43.9% austenite, 32.0% ferrite and 24.2% bronze. Dispersion-hardened copper particles with 47 vol % content precipitated inside the austenite grains while only 20 vol % of the dispersion-hardening NiAl particles precipitated in the ferrite grains. Transmission electron microscopy data indicate a coherent conjugation between crystalline lattices of these dispersion hardening particles and matrix. Such a composite structure provides 50%, on average, improvement of the tensile strength compared to that of austenitic steel obtained by electron beam additive technology without the addition of aluminum bronze. It was found that the contributions of various hardening mechanisms to yield strength of austenite, ferrite and bronze amounted to 959.3, 972.7 and 408.7 MPa, respectively. Bronze grains do not make a significant contribution to increase of the yield strength of the composite, except for its increase due to dislocation hardening. The main contributions to the increase of the composite yield strength are made by austenite grains due to grain-boundary, dispersion and dislocation hardening, and by ferrite grains due to grain-boundary, solid-solution and dislocation hardening.

Regularities of Friction Stir Processing Hardening of Aluminum Alloy Products Made by Wire-Feed Electron Beam Additive Manufacturing

Friction stir processing of additive workpieces in the sample growth direction (the vertical direction) and the layer deposition direction (the horizontal one) was carried out. The hardening regularities of aluminum-silicon alloy A04130 and aluminum-magnesium alloy AA5056 manufactured by electron beam additive technology were studied. For each material, 1 to 4 subsequent tool passes were performed in both cases. It was found that the formation of the stir zone macro-structure does not significantly change with the processing direction relative to the layer deposition direction in additive manufacturing. The average grain size in the stir zone after the fourth pass for AA5056 alloy in the horizontal direction was 2.5 ± 0.8 μm, for the vertical one, 1.6 ± 0.5 μm. While for the alloy A04130, the grain size was 2.6 ± 1.0 μm and 1.8 ± 0.7 for the horizontal and vertical directions, respectively. The fine-grained metal of the stir zone for each alloy in different directions had higher microhardness values than the base metal. The tensile strength of the processed metal was significantly higher than that of the additively manufactured material of the corresponding alloy. The number of tool passes along the processing line is different for the two selected alloys. The second, third and fourth passes have the most significant effect on the mechanical properties of the aluminum-magnesium alloy.

Fabrication of Conically Shaped CuCr1 Chrome Bronze Products by Wire-Feed Electron Beam Additive Manufacturing

The structure and properties of conically shaped products made of CuCr1 chrome bronze obtained by wire-feed electron beam additive technology have been investigated. The studies show that the organization of the structure in the samples fully corresponds to the peculiarities of the printing process and heat removal from the samples. The structure is represented by large grains elongated in the direction of heat removal. Chromium in the samples is mainly localized in the form of particles located between the dendrite arms. Near the substrate, intense mixing of the bronze with the substrate material (steel 321) is observed. The mechanical properties of the conical and cylindrical sample parts material are at a fairly close level. The samples are characterized by low values of yield strength, low values of tensile strength and high plasticity. Near the substrate, the mechanical properties of the specimens increase.

Structural design and performance evaluation of Ti6Al4V/5%Cu produced by electron-beam additive technology with simultaneous double-wire feeding

For the first time, the possibility of Ti6Al4V/5%Cu multi-material production by electron-beam additive technology (EBAM) with simultaneous feeding of two wires has been shown. The work shows the influence of Cu on the evolution of microstructure, phase composition and mechanical properties of Ti6Al4V/5%Cu. The simultaneous feeding of Ti and Cu wires during EBAM allows the refinement of coarse columnar grains and the formation of equiaxed ones. The Ti6Al4V/5%Cu microstructure is represented by a supersaturated solid solution of Cu (up to 5 at.%) in the α/β Widmanstätten structure. There is precipitation of Ti2Cu particles in the Ti6Al4V/5%Cu structure. Together with the effects of fine grain, solid solution, dispersion hardening and grain boundary wetting, the ultimate tensile strength of Ti6Al4V/5%Cu increased by about 20%, while the tensile strain decreased by three times.

Production of gradient intermetallic layers based on aluminum alloy and copper by electron-beam additive technology

This study presents the results of experimental work on the production and examination of samples of laminated polymetallic products made by wire-feed electron-beam additive technology using the technique of controlled filament feeding into the melt bath. The structure of the products based on M1 copper and AMg5 aluminum alloy combines metallic and intermetallic layers with the presence of a gradient transition between the phases. Inside the layers with a transition structure the distribution of intermetallic phases can be of different types. The microhardness values of the different structural constituents of the samples differ by more than a factor of 16. The mechanical properties of the material of the transition layers are characterized by low strength and low plasticity. In the structure of the intermetallic layers and at the boundary between them the formation of defects in the form of cracks and delaminations is observed.

Structure and phase composition features of nickel-based superalloy after electron beam additive process

In the present work, the structure and properties of products from heat-resistant nickel-based superalloy ZhS6U formed by wire-feed electron beam additive technology were investigated. Products were obtained under different parameters of electron beam additive process (accelerating voltage, beam current and movement speed of working table were varied). It was shown that a high speed of displacement leads to the formation of defects in the form of cracks and delamination of the obtained product from the substrate, which also leads to the appearance of cracks. It has been established that the greatest energy input leads to evaporation of aluminum (the main hardening γ’ phase). The phase composition of the additive product did not differ from the original material.

Modification of the Material Structure Produced by the Electron-Beam Additive Manufacturing by the Subsequent Friction Stir Processing

The work is devoted to the study of the formation of large blocks from aluminum alloy AA5056 by electron-beam additive technology with subsequent friction stir processing of the material. Conducted studies of the sample structure show that during the processing of additively produced samples there is a refinement of the material grain structure in the stir zone with the removal of defects such as pores and small discontinuities. Large defects of the additively produced material can be eliminated by the friction stir processing only partially, with the formation of defects such as the Lazy “S” or the joint line one in the stir zone.

The Formation of Bimetallic Materials by the Electron-Beam Additive Manufacturing

The structure of Cu-Ni system polymetallic materials samples produced by the electron-beam additive technology has been studied. Two types of samples were manufactured: with a smooth and sharp gradient. The separation effect of the nickel alloy from the copper substrate was found in a number of experiments. More intensive heating of the substrate before the first layer was applied, which resulted in the formation of a smoother transition zone from copper to nickel alloy, but did not solve the problem due to uncontrolled diffusion in the molten bath. The use of the multi-wire gradient printing with simultaneous feeding of two filaments allowed to form a smoother transition in the boundary zone.

Structure formation features of large block-shaped samples from the copper and aluminum alloy produced by the wire-feed electron-beam additive technology

In this work the study of the structure of samples made by the wire-feed electron-beam 3D printing from copper C11000 and aluminum alloy AA5056 was carried out. The presence of a dendritic structure typical of this method was revealed, as well as the presence of pores, cracks and other defects that occurred during printing. Mechanical properties of samples cut in the planar section are at a rather low level. The ultimate tensile strength of copper block samples varies between 165 and 187 MPa. The relative elongation of samples without pores is at 18%, but with the presence of pores it decreases sharply to 7%, while the strength is practically not decreased. The samples of alloy AA5056 demonstrate slightly higher mechanical properties: the strength is at the level of 190-192 MPa and the relative elongation is about 16-18%. In samples with defects such as large pores or discontinuities, the strength drops to almost zero.

Peculiarities of Structure Formation in Copper/Steel Bimetal Fabricated by Electron-Beam Additive Technology

In the present paper, the microstructure of heterogeneous material bimetal compound fabricated by wire-feed electron-beam additive technology from CrNiTi stainless steel and С11000 copper has been investigated. The bimetallic compound is characterized by the well-defined interface between the two materials and possesses two-phase transition areas on both sides of the interface. The heterogeneity of strength properties (microhardness) in the transition zones is associated with a solid solution hardening of the bimetal basis components and formation of composite structures in the transition zone of the bimetal: spherical inclusions of steel in the copper part and copper inclusions in the steel section. In the copper part of the bimetal sample, a heterogeneous grain structure is formed – areas with macroscale non-equiaxed grain structure and zones with spherical grains were observed. The heterogeneity of grain structure does not have significant influence on the yield strength, but affects the macroscopic deformation pattern of the bimetal copper part, as has been revealed by microstructural analysis of slip traces and grain structure calculated using the Hall–Petch relationship.