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AlCoCrFeNiTi0.5 high entropy alloy (HEA) coating with high hardness and excellent wear resistance was deposited on TC4 surface by electron beam cladding, and the process parameters, microstructure and properties of the coating were studied. The analysis shows that the microstructure of HEA coating is composed of dendritic (DR) and interdendritic (IR) phases. The IR phase, which is mainly composed of Fe and Cr, is confirmed to be BCC solid solution, while the DR phase is FCC solid solution with AlNi2Ti (or AlCo2Ti) structure. The grain orientation of the HEA coating is random, without obvious texture. Hardness gradually decreases from the upper part area of the HEA coating to the inner of the TC4 substrate. The hardness curve in the HEA coating region has some fluctuations, but the fluctuations are small, indicating a homogeneous microstructure. The average hardness of the HEA coating is 796.18 HV0.2, which is about 2.6 times that of the TC4 substrate. The HEA coating exhibits a higher coefficient of friction (COF) compared to the TC4 substrate. The average COF of HEA coating and TC4 substrate in the stable stage are 0.57 and 0.48, respectively. Wear loss of the HEA coating is 0.0657 mm3, about one tenth of that of TC4 substrate (0.6112 mm3). The hardness of the HEA coating is high, no obvious furrow is found, and its wear mechanism is considered to be a mixture of adhesive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys exhibit exceptional suitability for operating in environments characterized by corrosive agents and elevated temperatures. Strategic allocation of this expensive material solely to the functional surface areas yields significant economic advantages. The poor tribological property profile of Inconel 718 can be significantly improved through a boriding process. In this study, the possibility of combining a coating process with boriding technology and in situ heat treatment was investigated. Layers of Inconel 718 were deposited to an austenitic stainless steel using wire-based electron beam cladding (EBC) and subsequently subjected to boriding. Based on results from annealing experiments, boriding treatments were performed at various temperature/time regimens with the aim of inducing in situ age hardening during boriding. The focus was on the investigation of the influence of the temperature/time regime during boriding on the microstructure and hardness, as well as examining the wear and corrosion behavior of the resulting borided layers. The results showed that the desired target hardness range was achieved after in situ aging with all boriding variants. Furthermore, it was demonstrated that boriding significantly improved the wear resistance but decreased corrosion resistance. [ABSTRACT FROM AUTHOR]

The structure and properties of surface layers of billets from steel 12Kh18N9T formed by vacuum electron beam surfacing of powder mixtures are studied. The main alloying component is molybdenum in an amount of 40 wt.%. The structural and phase studies are made using optical and electron microscopes and an x-ray diffractometer. The microhardness and the wear resistance of the deposited layers are determined. The structure of the hardened surface layer is shown to contain phases Mo0.08Fe0.92, Mo0.9Fe0.1, Mo0.1Fe0.9, α-Fe and γ-Fe. The alloying with molybdenum raises the wear resistance of the steel by a factor of 1.8 and the heat resistance by a factor of 6.7. [ABSTRACT FROM AUTHOR]

In this study, Al21Co22Cr22Fe13Ni22 high-entropy coatings were produced on steel substrates by non-vacuum electron beam cladding of Co, Cr, and NiAl powders. The high-temperature oxidation behavior of the coatings was studied by holding the specimens at 900 °C in air. The microstructure and phase constitution of the samples were studied both in the as-cladded state and after the heat treatment. The microstructure was characterized using light microscopy (LM) and scanning electron microscopy (SEM). Synchrotron X-ray diffraction (SXRD) and energy-dispersive X-ray spectroscopy (EDX) were used to study the phase constitution of the coatings and the "coating-substrate" interface. The coating consisted of disordered bcc (A2), ordered bcc (B2), and disordered fcc (A1) phases. Annealing the coatings for 50 h at 900 °C led to the formation of fcc precipitates in the bcc dendritic grains and a mixture of fcc and σ-phase particles in the interdendritic regions. Needle-like nanosized B2-precipitates were formed due to annealing in the fcc grains at the coating/substrate interface. The microhardness at the top of the as-cladded coating was 585 HV and gradually decreased towards the substrate. A more uniform distribution of the microhardness was obtained after the annealing. Its average value was 441 HV. Rhomboid Cr2O3, needle-like Al2O3, and spinels of a different morphology were found on the surface of the samples after oxidation at 900 °C. [ABSTRACT FROM AUTHOR]

Some unavoidable factors in the operating environment could damage single-crystal components of nickel-based single-crystal superalloys. This work prepared an epitaxial growth NiCoCrAlYTa repaired coating without the columnar-to-equiaxed transition (CET) phenomenon on a nickel-based single-crystal superalloy by electron beam cladding. The microstructure of two cross-sections and two surfaces at different depths were characterized. Moreover, the formation mechanism of coating dendrite was revealed by studying the relationship between coating dendrite size, growth direction, and solidification rate. The microstructure evolution and crystal growth orientation of the coating were investigated. The microstructural investigation of the sample revealed that the dendrites' orientations on the coating's horizontal section were different, and its characteristics were highly visible on the surface of the coating. The crystal growth orientations of the coating on the vertical cross-section parallel/perpendicular to the scanning direction of the electron beam were also different. Moreover, the average primary dendrite arm spacing (PDAS) of the columnar dendrite in the different areas of the coating was different and increased from 2 μm to 4 μm. The oxidation resistance of the coating at 1000 °C was about three times higher than that of the substrate. [ABSTRACT FROM AUTHOR]

The paper describes a model of electron-beam cladding taking into account the gradual growth and shrinkage of the powder layer. The effective properties of the grown layer depend on the porosity and temperature. The calculation algorithm is based on an implicit difference scheme. The surfacing process turns out to be generally non-stationary, which necessitates a more detailed study of the interaction of different phenomena at different stages. The dynamics of the process, the surface layer relief, the porosity and the temperature are shown to depend on such parameters as the electron beam velocity along the surface and the scanning step. Some examples of calculations illustrating the model capabilities are given. [ABSTRACT FROM AUTHOR]

In this study, Al21Co22Cr22Fe13Ni22 high-entropy coatings were produced on steel substrates by non-vacuum electron beam cladding of Co, Cr, and NiAl powders. The high-temperature oxidation behavior of the coatings was studied by holding the specimens at 900 °C in air. The microstructure and phase constitution of the samples were studied both in the as-cladded state and after the heat treatment. The microstructure was characterized using light microscopy (LM) and scanning electron microscopy (SEM). Synchrotron X-ray diffraction (SXRD) and energy-dispersive X-ray spectroscopy (EDX) were used to study the phase constitution of the coatings and the “coating-substrate” interface. The coating consisted of disordered bcc (A2), ordered bcc (B2), and disordered fcc (A1) phases. Annealing the coatings for 50 h at 900 °C led to the formation of fcc precipitates in the bcc dendritic grains and a mixture of fcc and σ-phase particles in the interdendritic regions. Needle-like nanosized B2-precipitates were formed due to annealing in the fcc grains at the coating/substrate interface. The microhardness at the top of the as-cladded coating was 585 HV and gradually decreased towards the substrate. A more uniform distribution of the microhardness was obtained after the annealing. Its average value was 441 HV. Rhomboid Cr2O3, needle-like Al2O3, and spinels of a different morphology were found on the surface of the samples after oxidation at 900 °C.

NiAl-based intermetallic coatings were obtained using non-vacuum electron beam cladding on low-carbon steel. The structure of the coatings was investigated using optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). The coatings mostly consisted of grains elongated perpendicular to the substrates, with a strong <100> texture along the grain growth direction. The coatings contained about 14 at. % Fe, which appeared due to the partial melting of the steel substrate. At the bottom of the coatings, an inhomogeneous mixing zone with an increased concentration of Fe was formed; at the "substrate–coating" interface, a thick layer with a Fe50-Ni25-Al25 at. % composition was observed. The samples exhibited weight gains of 0.1, 0.8, 2.14, and 3.4 mg/cm2 after 100 h of oxidation at 700, 800, 900, and 1000 °C, respectively. The oxide layer contained α-Al2O3 and θ-Al2O3, and the presence of iron atoms contributed to the formation of a small amount of spinel. During the oxidation process, a layer with a high Fe content (~60 at. %) formed along the boundary between the oxide film and the NiAl-based material, which had a positive effect on the formation of a non-porous "oxide–coating" interface. [ABSTRACT FROM AUTHOR]

Ni60 electron beam cladding can play an important role in improving the properties of 7050 aluminum alloy. The cracking of the cladding layer, however, greatly affects the cladding quality. To solve this problem, the optimum range of cladding process parameters is determined by an experimental method: electron beam current [25–30 × 10−3 A], scanning speed [10–12 mm/s] and focusing current [700–720 × 10−3 A]. Through range analysis of the experiment results, the primary and secondary order of the influence of the cladding process parameters on the crack areal density is determined as follows: electron beam current > scanning speed > focusing current. A mathematical model of the crack areal density of the cladding layer is established based on the method of nonlinear regression, which is y = 4.1553 × 104 I2.2887V−0.8379I210.2675. It is shown that the model has obvious significance in the results of variance analysis, which can provide a basis for the selection of electron beam cladding process parameters. [ABSTRACT FROM AUTHOR]

Corrosion resistance of surface layers of structural steel 12KhN3A modified with chromium, nickel and titanium using the process of non-vacuum electron beam cladding is investigated. Tensile mechanical tests are conducted, the structural and phase compositions of the materials are analyzed, the total concentration of the alloying elements is determined. The corrosion resistance of layers with different compositions clad on steel 12KhN3A is studied under the action of nitric (65%), sulfuric (5%) and orthophosphoric (65%) acids. It is shown that the corrosion resistance of large-size steel billets can be raised by electron beam cladding of powder mixtures onto their surfaces. [ABSTRACT FROM AUTHOR]

Numerical simulations combined with electron beam melting were adopted to study the effect of the thickness of the preset coating on the quality of electron beam melting and forming of aluminum alloys. The research was carried out using ANSYS19.0 finite element analysis software to perform the numerical simulation of the temperature field and stress field during the process of electron beam melting of the Ni60 coating on 6061 aluminum alloy. The results show that the thicker the preset coating, the higher the surface temperature and the greater the melting depth and width of the melt pool, but the smaller the substrate melting depth, and the highest surface temperature obtained was 2536.05 °C. When the coating thickness reached 1.5 mm, the substrate essentially showed no change; otherwise, the thicker the preset coating, the greater the residual stress, and the maximum residual stress on the coating surface along the scanning direction appeared at the position near the boundary. Moreover, the maximum residual stress along the depth direction occurred at the interface. The electron beam cladding experiments showed that the 0.5 mm thickness of the coating resulted in a cracking phenomenon at the interface with the substrate, and the surface of the molten layer had more defects such as pores and pits; the 1 mm thickness of the coating had a good metallurgical bond with the substrate, and the surface of the molten layer was dense and flat; the 1.5 mm thickness of the aluminum alloy substrate did not melt, and the surface of the molten layer had more cracks. The numerical simulation was essentially consistent with the electron beam cladding experiment, and the forming quality was better when the preset coating thickness was 1 mm. [ABSTRACT FROM AUTHOR]

NiAl-based intermetallic coatings were obtained using non-vacuum electron beam cladding on low-carbon steel. The structure of the coatings was investigated using optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). The coatings mostly consisted of grains elongated perpendicular to the substrates, with a strong texture along the grain growth direction. The coatings contained about 14 at. % Fe, which appeared due to the partial melting of the steel substrate. At the bottom of the coatings, an inhomogeneous mixing zone with an increased concentration of Fe was formed; at the “substrate–coating” interface, a thick layer with a Fe50-Ni25-Al25 at. % composition was observed. The samples exhibited weight gains of 0.1, 0.8, 2.14, and 3.4 mg/cm2 after 100 h of oxidation at 700, 800, 900, and 1000 °C, respectively. The oxide layer contained α-Al2O3 and θ-Al2O3, and the presence of iron atoms contributed to the formation of a small amount of spinel. During the oxidation process, a layer with a high Fe content (~60 at. %) formed along the boundary between the oxide film and the NiAl-based material, which had a positive effect on the formation of a non-porous “oxide–coating” interface.

A major drawback in the application of AlCoCrFeNiCu high-entropy alloy (HEA) coatings is a susceptibility to hot-cracking, which is closely related to a grain boundary segregation due to the low melting point Cu component. Reducing or eliminating the grain boundary segregation of Cu is an effective means of reducing cracking in the HEA coating. In this study, blended and partial pre-alloyed powders were used as feedstock to fabricate the AlCoCrFeNiCu coating. The application of electron beam (EB) cladding to partial pre-alloyed powders, prepared by resistance seam welding (RSEW), resulted in an appreciable reduction of crack density in the coating. This response is attributed to the formation of Ni 3 Al and Al 4 Cu 9 promoted by the relatively low heat generated during the RSEW process. In subsequent EB cladding, nanoscale Me 3 Al (Me = Cu, Ni) replaced the Cu-rich phase at grain boundaries. The hardness and wear resistance of coatings using partially pre-alloyed powders were 17.2 % and 15.8 % higher, respectively, than blended powders. The findings of this study indicate that the use of partial pre-alloyed powders can offer a new effective approach to reducing the hot cracks in EB cladding AlCoCrFeNiCu HEA coatings. [Display omitted] • AlCoCrFeNiCu coatings were fabricated by blended and partial pre-alloyed powders. • Cracks were reduced using partial pre-alloyed powders by electron beam cladding. • Ni 3 Al and Al 4 Cu 9 phases reduced the interdendritic segregation of Cu in RE coatings. • Wear resistance of RE coating was optimal 20.4 % higher than EB coating. [ABSTRACT FROM AUTHOR]

The study investigates an electron beam cladded coating of nitrogen-alloyed austenitic steel (24.4Cr, 16.4Mn, 0.18Ni, 1.1Si, 0.57С, 0.7N, rest Fe (wt %)). Cladding was performed by a continuous low-energy (27 keV) and low-current (0.02–0.04 A) focused electron beam on an electron beam system at a residual pressure of 0.1 Pa. The microstructure, phase composition, and chemical composition of the coating were examined by OM/AES/XRD/SEM/EDS methods. The coating has no pores and is characterized by high work hardening and wear resistance. The formation of М7(С, N)3 carbonitrides in the steel plays a crucial role in the control of the structure and wear resistance of the applied coating, because carbonitrides are able to distinguish between the lattice curvature zones and the stable translationally invariant lattice. Frictional loads arising during wear trigger a γ → α′ transformation. With increasing frictional load, the coefficient of friction decreases. [ABSTRACT FROM AUTHOR]

An important parameter of non-vacuum electron-beam cladding is the surface density of the input energy that depends on the beam current and the specimen travel speed. The paper presents results of investigation of the effect of the heat input on the structure and properties of composite coatings fabricated by electron beam cladding. The modes of cladding with beam currents of 25 and 40 mA and specimen travel speed varying within 0.5–2.0 cm/s have been studied. It was revealed that the thickness, the dendrite grain size, and the microhardness of the coatings increased, and the volume fraction of the eutectic decreased with increasing specific electron beam power. It is shown that for a low heat input, an austenitic-martensitic structure is formed with carbides in the eutectic and martensite needles. For a large heat input, an austenitic structure with eutectic carbide network is formed. The martensitic structure is formed only along the coating-substrate interface as a result of intense heat removal deep into the substrate material. [ABSTRACT FROM AUTHOR]

Electron beam cladding in vacuum was carried out according to the Archimedes spiral on copper billet of 80 mm diameter and 10 mm thickness. The authors have used a mixture of copper and chromium powders with chromium content fromf 20 to 50 wt. % for electron-beam cladding. Copper and chromium powder particle size was in the range from 90 to 125 microns. The comparison study of microstructures generated on the contact materials by vacuum arc surface melting and the microstructure of contact materials after electron beam cladding was carried out. The analysis of the microstructures was carried out using a scanning electron microscope Leo Evo 50 equipped with microanalysis by secondary and backscattered electrons. The authors identified the areas of preferential combustion of cathode spots on the surface of the sintered contact material. It is shown that copper evaporates preferentially during the surface melting of the contact material by vacuum arc and the surface layer is enriched in chromium. Surface melting zone has a non-uniform depth on the contact material. Surface melting areas of contact material alternate with areas having the original structure. In the surface melting areas a bimodal structure is formed. It consists of primary and secondary chromium precipitates of either micron or submicron size, respectively. CuCr clad coatings demonstrate a bimodal structure similar to the structure of the surface layer contacts of vacuum switches fused by short circuit currents. Thus, it is shown that the electron-beam cladding is self-organizing structure of the contact material similar to the surface layer structure of vacuum circuit breakers contacts formed at their operation.

The methods of optical and scanning electron microscopy, micro-X-ray analysis, and analysis of backscattered electron diffraction are used to study the influence of the input energy on the structure and phase composition of coatings obtained by high-energy electron cladding of a mixture of chromium carbide and titanium carbide powders on low-carbon steel in the open air. A correlation between the structural-phase state of coatings and their microhardness is established. The role of titanium carbide particles in the formation of the structure and changes in the microhardness of coatings is discussed. [ABSTRACT FROM AUTHOR]

Electron beam cladding (MoNbCoCrAl x Si 0.2) 70 Ti 30 RHEAs coatings with different Al contents on the surface of Ti600 alloy, and their microstructure and properties were investigated. Two solid solution phases, A2/B2-BCC1 and A2-BCC2, and precipitated phases (Ti,Mo,Nb,Al) 5 Si 3 -IMC were found. The mechanical properties and wear resistance of RHEAs coatings increase and then decrease with increasing Al. The mechanism of the change in mechanical properties and wear resistance is based on the strong and weak relation between solid solution strengthening and precipitation strengthening. The improvement of high-temperature oxidation resistance is due to the promotion of Al 2 O 3 formation at the early oxidation stage. • The (MoNbCoCrAl x Si 0.2) 70 Ti 30 RHEAs coatings with different Al contents are fabricated on Ti600 by EBC. • The RHEAs coatings are composed of BCC1+BCC2 solid solution phases and IMC precipitated phase. • The mechanical properties and wear resistance of RHEAs coatings are affected by the number and size of precipitates. • The high temperature oxidation resistance of RHEAs coatings and the mechanism are studied. [ABSTRACT FROM AUTHOR]

This study employs a continuous scanning electron beam to deposit AlCoCrFeNi composite cladding on the surface of 253MA austenitic stainless steel to enhance its surface properties. The characteristics were examined through a scanning electron microscope (SEM), backscattered electron diffraction (EBSD), and white light interferometric three-dimensional surface profile instrument. This study investigated the effect of electron beam process parameters on the surface organization and mechanical properties of 253MA steel. The sample surface was divided into four zones: overlay, bonding, thermal influence, and substrate, according to the results. Coarse columnar and island-shaped crystals composed the overlay zone, while equiaxed austenite grains primarily constituted the substrate. With the increase of the beam current, the microstructure's grain size decreased, the substructures increased, and the BCC phase transformed into the FCC phase. The grain size slightly decreased, substructures changed marginally, and the BCC phase increased as the scanning speed increased. Additionally, the microhardness and mechanical properties of the overlay layer increased significantly, and wear volume and wear rate decreased progressively with the increase in beam current and scanning speed. At a beam current of 18 mA and a scanning speed of 200 mm/min, the surface hardness of 253MA steel reached the maximum value of 520 HV. When the beam current was 24 mA, and the scanning speed was 200 mm/min, the wear volume and wear rate of the overlay sample were minimal, accounting for 37.4% of the original sample's, and its wear resistance was 2.67 times more than that of the substrate. • Unique microstructure in cladding zone: coarse and island-shaped crystals; equiaxed austenite matrix. • Beam current refines grains, enhances substructure, transforms BCC to FCC phase. • Scanning speed causes minor grain refinement, limited substructure changes, increased BCC phase. • Higher beam current and scanning speed boost microhardness, mechanical properties, wear resistance. [ABSTRACT FROM AUTHOR]

• Al–Mg–WC composite coating obtained by non-vacuum electron-beam cladding. • Alloying of Al–6 %Mg with WC particles leads to the formation of Al 12 W, Al 4 W phases. • Density, structure, microhardness and wear resistance of aluminum matrix composite. The composite coating with a thickness of 5.2 ± 0.3 mm was obtained by non-vacuum electron-beam cladding of WC powder on an Al–6 % Mg alloy. A highly concentrated relativistic electron beam exposure to the alloying system leads to partial dissolution of tungsten carbide in the melt pool, causing interfacial interactions and new phases formation. The microstructure and phase composition of composite coating was studied using scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction analysis. The microhardness of the composite coating is 1.3 times higher than substrate material and wear resistance is 1.13 times higher than Al–6 % Mg alloy. [ABSTRACT FROM AUTHOR]

Titanium and titanium alloys are highly important structural materials for many industries where low density in combination with high mechanical strength and corrosion resistance are required. However, titanium is not applicable for tribological or high temperatures purposes due to its interaction with atmospheric gases and friction seizure during the contact with most metallic materials. To protect the surface of titanium and improve its wear resistance intermetallic coatings can be applied. In this study, the Ti-Al intermetallic layers were fabricated on Ti surface by electron beam melting of Al and Ti powders. By variation of Al/Ti ratio in the initial powders it was possible to control elemental and phase composition of the layers. The formation of TiAl, Al 2 Ti and Ti 3 Al phases was observed in the layers. Independently on Al content the layers had lamellar type of structure. Microhardness, wear resistance and oxidation resistance were measured to evaluate the quality of the layers. The microhardness and wear resistance were in good agreement with each other. The coating, consisted of pure Ti 3 Al phase, demonstrated the highest level of these properties. Oxidation resistance of the coatings increased proportionally to the aluminium content due to formation of alumina in oxide scale. [ABSTRACT FROM AUTHOR]

The aim of the presented work was to carry out the research on electron beam cladding with a wire as a ller material. The scope of the work was to investigate the influence of technological parameters such as: wire feed rate, beam current, travelling speed, acceleration voltage on stability of the cladding process and geometric dimensions of the padding welds. The research revealed that, at low beam currents, the cladding process is unstable. The padding weld reinforcement is nonuniform. Irregularity of the width, height and straightness of the padding welds can be observed. At too high acceleration voltage and beam current, burn-through of plate and excess penetration weld can be revealed. The study also showed that increase of the cladding rate (travelling speed on the table) results in reduced face width and padding weld reinforcement. in polish Napawanie wiązką elektronów przy użyciu drutu Celem pracy było przeprowadzenie badań w zakresie napawania przy użyciu wiązki elektronów i materiału dodatkowego w postaci drutu. Zakres pracy obejmował zbadanie wpływu warunków technologicznych tj.: prędkości podawania drutu, natężenia prądu wiązki, prędkości przesuwu, napięcia przyspieszającego na stabilność procesu napawania oraz wymiarów geometrycznych napoin. Przeprowadzone badania wykazały, iż przy niskim natężeniu prądu wiązki proces napawania nie jest stabilny. Nadlew nie jest równomierny, można zaobserwować nierównomierność szerokości, wysokości i prostoliniowości nadlewu. Przy zbyt wysokim napięciu przyspieszającym oraz natężeniu prądu wiązki można zaobserwować przetopienie płyty próbnej na wskroś i wyciek w grani. Przeprowadzone badania wykazały również, iż wzrost prędkości napawania (przesuwu stołu) powoduje zmniejszenie szerokości lica oraz wysokości nadlewu.

In this study, non equiatomic FeCrNiCoMoW MEA composite coatings were successfully prepared by electron beam cladding Fe-based amorphous powders. The effects of WC-10Co amounts (0–30 wt%) on the microstructure, mechanical properties, and electrochemical property of the MEA composite coatings were investigated. The added WC-10Co decomposed, and the original amorphous alloy was completely crystallised. The composite coatings primarily comprised the face-centred cubic (FCC) matrix, M 23 C 6 (M = Cr, Mo, Fe, or W) and WC particles. The average hardness of the composite coatings gradually increased with increased WC-10Co amounts from 5.66 ± 1.09 GPa to 8.02 ± 2.54 GPa. The composite coating with 30 wt%WC-10Co showed optimal hardness and wear resistance, which were approximately 4 and 2 times that of the substrate, respectively. The wear mechanism changed from severe adhesive wear for 0 wt% WC-10Co composite coating to abrasive and slight adhesive wear for 10–30 wt% WC-10Co composite coatings. The 10 wt% WC-10Co coating exhibited the best corrosion resistance in 3.5 wt% NaCl solution. The number of corrosion pits decreased with the addition of WC-10Co increased, and corrosion occurred in the Cr-depleted regions. Solid solution, dislocation, WC particles and M 23 C 6 nanoprecipitates were responsible for the improvement in mechanical properties and corrosion resistance of the coatings. • Non equiatomic FeCrNiCoMoW MEA composite coatings were prepared on the surface of 304 steel by the electron beam cladding. • The microstructure, mechanical properties, and electrochemical properties of the coatings were investigated. • The coatings mainly comprised face-centred cubic matrix and M 23 C 6 (M = Cr, Mo, Fe, or W). • The coating exhibited excellent wear and corrosion resistance performances. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) are currently considered as promising materials for a wide range of applications, including high-temperature use. Since HEAs contain a large number of expensive elements, producing HEA-based coatings seems to be a reasonable approach from an economic point of view. In this study, non-vacuum electron beam cladding was used for the first time to produce CoCrFeNiX layers (where X = Al, Cu or Mn) on a surface of low-carbon steel. As-received coatings had a columnar grain structure with a 〈100〉 fiber texture. The CoCrFeNiCu cladding layer consisted of two fcc phases: Cu-enriched phase was observed in the interdendritic regions, and the Cu-depleted phase was found in dendrites. The CoCrFeNiMn coating had a single-phase fcc structure. CoCrFeNiAl alloy consisted of bcc and B2 phases. The hardness of the Cu and Mn-containing coatings was 190 and 186 HV, respectively. The hardness of the CoCrFeNiAl coating was 570 HV, which is 3.4 times higher compared to the material of the substrate. High-temperature oxidation tests carried out at 850 °C for 45 h revealed that oxide layers formed on the tested samples had a gradient structure that consisted of several different sublayers. The total mass gain due to high temperature oxidation was 2.29 mg/cm2, 2.04 mg/cm2, and 0.60 mg/cm2 for the CoCrFeNiCu, CoCrFeNiMn, and CoCrFeNiAl samples, respectively. The mass gain of the base material over the same period of time was 41.01 mg/cm2. The CoCrFeNiAl coating had the best oxidation resistance due to the formation of a dense Al 2 O 3 scale. We show that non-vacuum electron beam cladding can be used to produce an HEA-based coating with a different chemical composition. The thickness of coatings in a single pass cladding can be as high as 1.8 mm. CoCrFeNiAl is a suitable coating for low-carbon steel in applications where high hardness and oxidation resistance are required. • HEA-based coatings were fabricated by non-vacuum electron beam cladding. • Coatings were produced from Co + Cr + Ni + X (X = Al, Cu, Mn) powders on Fe-based substrate. • Coatings possessed the columnar grain structure with a <100> fiber texture. • Gradient oxide layers were formed on the coatings during oxidation at 850 °C. • CoCrFeNiAl coating possessed the best oxidation resistance compared to other samples. [ABSTRACT FROM AUTHOR]

The refractory high-entropy alloys (RHEAs) possess excellent mechanical properties and electron beam cladding (EBC) has the advantages of vacuum protection and higher energy utilization. In this study, the Mo 20 Nb 20 Co 20 Cr 20 (Ti 8 Al 8 Si 4) RHEA coatings under different cladding currents (16, 17, 18,19 mA) are fabricated by EBC to improve the surface wear resistance of the Ti600 substrate. The microstructure and phase structure of RHEA coatings are investigated by OM, SEM, XRD, TEM. The mechanical properties of tcoatings and substrate are studied by microhardness, nanoindentation and dry wear test. The results show that the HEA coatings involve four main phases: BCC1(Mo,Nb,Al-rich-A2/B2), BCC2(Co,Cr,Ti-rich-B2), IMC1(Laves phase-CoTi) and IMC2((Ti,Nb,Zr) 5 Si 3), respectively. With the cladding current increasing, the dilution rate of the substrate increases to cause the Ti content within coatings to rise. The size of BCC1(DR regions), IMC1 and IMC2 becomes larger and the microhardness, nanoindentation hardness, elastic modulus and room-temperature creep resistance decrease. The properties improvement of the coating is attributed to the solid solution, second phase and precipitation strengthening caused by the solid solution structures and intermetallic compounds. The maximum microhardness of the coatings at current 16 mA is 1150 HV 0.2 , more than 3 times that of the substrate and the friction coefficient of Ti600 is 2.16 times that of current 16 mA, which suggests that the Mo 20 Nb 20 Co 20 Cr 20 (Ti 8 Al 8 Si 4) RHEAs can be used as an excellent wear-resistant coating with broad application prospect. [Display omitted] • The Al-containing Mo 20 Nb 20 Co 20 Cr 20 (Ti 8 Al 8 Si 4) RHEA coatings are fabricated on Ti600 by EBC. • Mo 20 Nb 20 Co 20 Cr 20 (Ti 8 Al 8 Si 4) RHEA coatings are composed of BCC1+BCC2 solid solutions and IMC1+IMC2 intermetallic compounds. • The RHEAs exhibits better mechanical properties than substrate and deteriorate as cladding current increases. • The strengthening mechanisms is a mixture of solid solution + second phase and the wear behaviors is mainly abrasive wear. [ABSTRACT FROM AUTHOR]

The structure and tribological properties of commercially pure titanium (cp-Ti) samples after non-vacuum electron beam surface alloying with carbon were studied. Two types of powders were used to introduce carbon in surface layer of cp-Ti: titanium carbide (TiC) and mixture of pure titanium and graphite (“Ti + C”). Single layer and multilayer coatings were studied. Application of electron beam for alloying provided cladding rate of 4.5 m 2 /h. The thickness of the clad coatings was 1.6–2.0 mm. The main phases received after “Ti + C” powder cladding were α-titanium, TiC, and retained graphite. In the samples obtained by cladding of TiC, graphite was not observed. A factor determining the microhardness and tribological properties of the cladded layer was the volume fraction of TiC. Maximum coating microhardness of 8 GPa was obtained by cladding of single layer of TiC powder or two layers of the “Ti + C” mixture. Two types of tests were carried out to evaluate the wear resistance of the samples. In friction tests against loose abrasive particles, the wear rate of the best samples was 9.3 times lower than that of cp-Ti. In wear tests using fixed abrasive particles, the relative wear resistance of the best samples was 2.3 times higher than that of cp-Ti. [ABSTRACT FROM AUTHOR]

Highlights: [•] We study the abrasive wear resistance of composite coatings. [•] We found a multimodal size distribution of carbide particles in the coatings. [•] Aging and self-aging by thermocycling serve to precipitation of fine carbides. [•] Wear resistance is improved with the carbide multimodal size distribution. [•] Wear resistance is improved by extra aging the composite coatings. [ABSTRACT FROM AUTHOR]

High-entropy alloys have been widely studied as a new and excellent material in the field of surface protection. To improve the low surface hardness and wear resistance of Ti600 alloy, AlCrTiNbMo high-entropy alloy (HEA) coating was prepared by electron beam cladding. The phase structure and microstructure showed the presence of two BCC solid solution phases A2 and B2 within HEA coating. Laves phase Ti 3 Al and intermetallic compound Mo 3 Al 8 were also present in the coating. The results of hardness and wear resistance tests showed that the microhardness of coating is 813.5 HV 0.2 ，while substrate is 370.7 HV 0.2. The mass loss of coating is only 1.02 mg after wear test, while the mass loss of Ti600 is 38.81 mg. There are cracks and delaminations on the worn surface of Ti600, and wear mechanism is a mixture of micro-ploughing and micro-cutting. The worn surface of HEA coating contains only shear surface traces, and the wear mechanism is micro-cutting. The width and depth of grooves on the worn surface of HEA coating are nearly 10 times that of Ti600 substrate. AlCrTiNbMo HEA coating can be used as an excellent wear-resistant coating with wide application prospect. • A method of AlCrTiNbMo HEA coating prepared by EBC on Ti600 is proposed. • Two BCC HEA microstructure disordered A2 and ordered B2 is fabricated by EBC. • The actual diffraction spots and lattice parameters of A2 and B2 are calculated. • The HEA coating has better wear resistance, and the mechanism is clarified. [ABSTRACT FROM AUTHOR]

Abstract: The effect of heat aging treatment on structural-phase composition and properties of austenitic composite electron-beam clad coatings has been studied. The rational aging schedule has been developed both to retain the austenitic matrix and provide multimodal carbide particles' size distribution throughout the clad metal volume. It is shown that vanadium carbide precipitates in manganese- and nickel-containing matrices in the form of isolated equiaxial particles of the mean size 94nm and ~1μm, respectively. Such a structural-phase state becomes feasible by combining the electron-beam cladding and heat treatment conditions. Wear resistance of coatings with multi-modal carbide size distribution has improved as compared to that of the non-aged coatings. [Copyright &y& Elsevier]

• WC-Ni 3 Al composite coatings with a volume fraction of WC particles of 18 % and 31%. • Microhardness of coatings varies from 5.198 GPa to 5.986 GPa. • Wear resistance of coatings is 2.2 times higher than Ni 3 Al. • CaF 2 + LiF flux reduces the loss of WC during cladding. The non-vacuum electron beam cladding technique was used to fabricate composite coatings with WC on the surface of Ni 3 Al intermetallic. The microstructure and phase composition of composite coatings were studied using scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction analysis. The results showed a good metallurgical bond of WC particles with the Ni 3 Al intermetallic matrix. Addition of CaF + LiF flux mixtures in the initial cladding powder reduces the loss of tungsten carbide powder compared to MgF 2 flux during electron-beam processing. Effect of tungsten carbide volume fraction, particle size and shape on the microhardness, wear mechanism of composite coatings was demonstrated. The microhardness of produced composite coatings was 1.3–1.5 times higher than substrate material and wear resistance was 2.2 times higher than Ni 3 Al. [ABSTRACT FROM AUTHOR]

Single, double, and triple-layer WC-40Co coatings were prepared by electron beam (EB) cladding to improve the wear resistance of Ti-6Al-4V. The microstructure, microhardness, wear resistance, and corrosion resistance of the coatings were investigated. The results demonstrated that the three types of coatings consisted of β (Ti, W), TiCo, (Ti, W) C 1-X , (W, Ti) C 1-X , and a small amount of Ti 2 Co. The core/shell structure of (W, Ti) C 1-X / (Ti, W) C 1-X was observed by TEM, and the phase interfaces were studied. The hardness and wear resistance of triple-layer coating was the highest, and its wear resistance was improved by 11.5 times that of the substrate. The wear mechanisms of the substrate, single- and double-layer coating was oxidative and abrasive wear, while the triple-layer coating exhibited abrasive wear. The corrosion resistance of the single- and double-layer coatings was better than that of the substrate; however, the triple-layer coating surface was significantly damaged owing to the cracks. • Multilayer WC-40Co coatings were prepared on Ti-6Al-4 V using electron beam cladding. • The microstructure characterizations of the coatings were investigated. • Formation mechanisms of (W, Ti)C 1-X /(Ti, W)C 1-X core/shell structure were investigated. • The triple-layer coating exhibited best wear but worst corrosion resistance performance. [ABSTRACT FROM AUTHOR]

To better control the Inconel617 electron beam cladding solidification process, a three-dimensional temperature field model was built to simulate the temperature gradient, cooling rate, and solidification rate in the solidification process and take a deep dive into the solidification behavior, as well as the calculation of the solidification characteristic parameters at the edge of the molten pool and then predict the solidification tissue structure. The study shows that the largest temperature gradient occurred in the material thickness direction. The self-cooling effect of the material dominated the solidification of the alloy layer; the cooling rate depended on the high-temperature thermal conductivity of the material and the self-cooling effect of the matrix, and the maximum cooling rate in the bonding zone was 1380 °C/s. The steady-state solidification rate was equal to the moving speed of the heat source; the solidification characteristics of the solidification process at the edge of the molten pool increased with the distance from the surface: the cooling rate decreased from 1421.61 to 623 °C/s, the temperature gradient increased from 0.0723 × 106 to 0.417 × 106, and the solidification rate decreased from 0.01 to 0 m/s. The prediction was made that the small and thin equiaxed crystals are on the top, a thin and short dendritic transition structure in the middle, and relatively coarse dendrites at the bottom. Experiments confirmed that the solidification tissue structure is basically consistent with the simulation law. [ABSTRACT FROM AUTHOR]

In this study, WC-10Co/Ti-6Al-4V coatings were fabricated under varying cladding voltages via electron beam cladding technology. The microstructure, microhardness, and wear performance of the composite coatings were studied. In addition, temperature field simulations were performed for the cladding process applying ABAQUS. The thickness of the coatings ranged from 350 to 850 μm. The presence of α-Ti, (Ti, W)C 1-X , and small amounts of WC, TiC, (W, Ti)C 1-X , W 2 C, and β-Ti in the coatings was confirmed. WC and TiC were partially dissolved and, in accordance with the simulated temperature field, resulted in the appearance of (W, Ti)C 1-X around the WC particles. Moreover, the consumption of C atoms was beneficial for the diffusion of W atoms into the TiC lattice to form (Ti, W)C 1-X. In the comparison of experimental and numerical simulation results, it was found that a deeper penetration and further settlement of WC particles was observed experimentally, when a higher cladding voltage was applied. The coating prepared under 65 kV exhibited the best mechanical performance and its friction mechanism entailed abrasive and adhesive wear. • WC-10Co/Ti-6Al-4V composite coatings were fabricated via electron beam cladding. • Microstructures of the coatings were characterized. • Formation mechanisms of (Ti, W)C 1-X and (W, Ti)C 1-X were investigated. • The coating fabricated at 65 kV exhibited best wear resistance performance. [ABSTRACT FROM AUTHOR]

In this study, the non-vacuum electron beam (EB) technology was used to clad commercially pure (CP-) Ti with Ta and Nb. The microstructure of the samples was characterized using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The cladded layers were 1.7–2.7 mm thick and had a dense defect-free structure. Compositional inhomogeneity caused by dendritic liquation was observed in the cladded layers. High cooling rates during non-vacuum EB cladding led to the formation of the α', α", β, and ω metastable phases in the samples. The nanoscale ω phase was found in the regions with a high amount of Ta and Nb. Due to the increase in the Nb and Ta content, the microstructure of the samples was refined, and the microhardness increased from 330 HV to 400 HV. The impact toughness of the materials with cladded layers remained at a sufficiently high level (180–250 J/cm2). Corrosion tests carried out in hot nitric acid revealed that the addition of 15% Ta and 11.3% Nb to Ti decreased the corrosion rate from 0.104 mm/year to 0.004 mm/year, which was related to an increase in the fraction of Ta and Nb oxides in the oxide film. The produced materials can be recommended as a relatively cheap alternative for nuclear waste recycling when a hot solution of nitric acid is used. • Ti Ta Nb cladding layers were produced by non-vacuum electron beam technology. • All samples had a dense defect-free structure. • Increasing the Moeq from 1.9 to 8.7 led to the structure changed from α′ + β to α″ + β + ω. • The corrosion rate of the cladded layer was 26 times lower compared to CP-Ti. [ABSTRACT FROM AUTHOR]

• The composite coatings with and/or without refractory modifier were fabricated by electron-beam cladding. • Influence of modifiers on α → γ transformation of Fe phase was investigated. • Compared to chromium carbide coatings, modified coatings were 9–10 times more wear resistant. Chromium carbide-based coatings with and without TiC and TiB 2 modifiers were fabricated by non-vacuum electron-beam cladding. Addition of the modifiers to the initial Cr 3 C 2 powder mixture led to a change in the phase composition, microhardness and wear resistance of the composite coatings and the α → γ transformation of Fe. TiC and TiB 2 particles formed the many crystallization centers in composite coatings, which led to a refinement of their microstructure. Larger TiC particles compared to the TiB 2 particles were formed in the coatings as a result of melt crystallization. TiC modifier caused a decrease in the size of dendrites, while TiB 2 led to a transition from a coarse dendritic structure to an equiaxed one. The coatings with TiC modifier demonstrated the maximum microhardness, and TiB 2 coating had increased wear resistance. [ABSTRACT FROM AUTHOR]

A unique process to prepare composite coating on titanium alloy by electron beam cladding is explored for improving durable oxidation resistance. The composite coating can be divided into two layers, including in-situ fabricated transition layer and pure Al layer. The isothermal oxidation tests are carried out at 973 and 1073 K. The composite coating reduced the oxidation rate to approximately 1/10 and 1/4 that of the substrate due to formation of Al 2 O 3. It can be obtained by the oxidation rate that the diffusion coefficient of composite coating is 4 × 10 − 20 m2/s, which is lower than 1 × 10 − 18 m2/s of the substrate. It indicated that the composite coating improves the oxidation resistance by inhibiting the diffusion of O. Although the oxidation rate of pure Al coating is similar to that of composite coating, the largest bonding force and completed structure after 20 cycles thermal shock of composite coating reveals that composite coating can improve the durability of oxidation resistance due to providing match CTE, which will improve the oxidation resistance further. • The composite coatings are composed of the middle transition layer and a pure Al layer via EB cladding. • The preparation technology provides a method to inform α-Al 2 O 3 at the surface. • The composite coatings are effective to protect TC11 from the inward and outward oxidation at 700 and 800 °C. • Mechanisms for improving oxidation resistance and bonding performance are discussed in detail. • The final oxidation rate is 0.0002 and 0.0022 mg2/cm4 ⋅ h at 700 and 800 °C. [ABSTRACT FROM AUTHOR]

The high passivation capacity of austenitic stainless steels results in excellent corrosion resistance in a wide variety of corrosion media. However, the tribological properties of these steels are insufficient due to their low hardness and high susceptibility to adhesive wear. To improve the wear behavior of austenitic steels while maintaining corrosion resistance, thermochemical processes such as nitriding or nitrocarburizing can be used. Such processes can be carried out as single procedures or in combination with coating techniques. Herein, the results of a new combination treatment consisting of the electron beam cladding (EBC) of a Co‐based alloy with subsequent gas nitrocarburizing (GNC) are presented. The effects of the beam deflection technique on the microstructure and phase formation of the cladded wear protection layer, the resulting hardness as well as the dilution ratio and the bonding of this layer to the base material are demonstrated. The subsequent gas nitrocaburizing leads to the formation of an ≈10 μm‐thick surface layer enriched with nitrogen and carbon. The significant improvement in wear resistance compared with the untreated base material is demonstrated by abrasive and adhesive‐abrasive wear tests. Corrosion resistance is investigated by recording current density—potential curves and long‐term tests in corrosive media. [ABSTRACT FROM AUTHOR]