Powder Welding Research Articles

Review on Plasma Atomizer Technology for Metal Powder

The application of plasma process is growing field covering a wide range of activities, from welding technology, coating technology, deposition technology, manufacturing technology of metal powder, and other important engineering technology. The manufacture of metal powders can be generated from the process of gas atomization, water atomization, plasma atomization, and plasma rotating electrodes process atomization. In the process of plasma atomization provides advantages in addition to producing round powder, it is also very potential for efficient processing and recycling of used and alloy materials, thus saving fuel and essential materials. These operations will have a continuing impact on our industrial society as a whole. The industry of future metal powder manufacturers that utilize plasma atomization technology is an investment strategy that has a great opportunity to grow rapidly. A variety of plasma processes for the manufacture of metal powders will be reviewed in this paper, among others, are plasma atomization and plasma rotating electrodes process atomization. They are all potentially able to control and to produce of metal powders of spherical particles, making it very profitable on powder technology applications. The purpose of this review is to summarize and provide future research for activities in the field of metal powders by plasma atomization processes. The emphasis on plasma engineering technology future research in powder making available for exploration and research needs to be met so that these future research can be realized. Finally, the future challenges of automation from the use of plasma atomization technology for additives manufacturing, powder welding and medical manufacturing.

Balance beams of caterpillar vechicals properties recovered by plasma powder weld deposition

Balance beams of caterpillar vechicals properties recovered by plasma powder weld deposition

A strategy for improving the mechanical properties of FSWed joints of non-heat-treatable Al alloys through a combination of water cooling and particle addition

In this paper, we developed a new process to improve the mechanical properties of FSWed joints of non-heat-treatable Al alloys through a combination of water cooling and particle addition. 5-mm-thick AA5083-H112 non-heat-treatable Al alloy plates were joined by friction stir welding (FSW). The whole FSW process was performed underwater with titanium (Ti) powders incorporated into the nugget zone (NZ), which is referred to as the underwater friction stir powder welding (UFSPW). The microstructure and mechanical properties of the UFSPW joints were investigated, and compared with the conventional FSW joints without Ti particle addition. The results revealed that compared with FSW joint, the area around the NZ of UFSPW joint was much less influenced by the thermoplastic deformation taking place in the NZ. Also, Ti particles with the excellent Ti/Al interfacial bonding, were uniformly scattered into the NZ of UFSPW joint, which was composed of ultrafine recrystallized grains with the average size of ∼0.8 μm. Compared to BM, the NZ of UFSPW joint exhibited markedly improved hardness while the hardness of the NZ of FSW joint increased slightly, with a slight hardness reduction occurring in a local area around the NZ. The YS and UTS of UFSPW joint was significantly increased when compared to that of FSW joint fracturing at the advancing side of NZ, and even up to that of the BM with the fracture occurring at the BM. Such obvious enhancement in strength originates from the creation of ultrafine grains and the well-distributed Ti particles.

Выбор режимов напекания металлических порошков на основе никеля и железа при комбинированном методе восстановления бронзовых втулок

Выбор режимов напекания металлических порошков на основе никеля и железа при комбинированном методе восстановления бронзовых втулок

Metallurgical features of the formation of a solid-phase metal joint upon electric-circuit heating

The thermodynamic conditions of formation of a joint between metals using the solid-phase methods of powder metallurgy, welding, and deposition of functional coatings upon electric-current heating of the surfaces to be joined are studied. Relations are obtained to quantitatively estimate the critical sizes of the circular and linear active centers that result in the formation of stable bonding zones.

Analysis of Particle Distribution in Milled Al-Based Composites Reinforced by B4C Nanoparticles

In the present work, high-energy ball milling was employed to synthesize Al-(5-10 wt.%)B4C nanocomposite. To do this, two sizes of particles of 50 nm as nanoparticles (NPs) and 50 μm as coarse particles (CPs) were used. The morphology and microstructure of the milled powders were characterized using particle size analyzer, SEM, TEM and EDX techniques. It was found that milling time, B4C particles size and their content strongly affect the characteristics of powders during milling process. The breaking and cold welding of powders was recognized as two main competitive actions during the milling process that influence the microstructural evolutions. It was found that the presence of CPs led to the formation of microcracks which promote the fracture process of Al powders. The dominated mechanisms during the fabrication of composites and nanocomposites were discussed. Also, the theoretical issues regarding the changes in morphology and distribution of B4C particles in CPs and NPs are clarified.

Determination of influence of laser welding modes and powder material composition on wear resistance of coatings

The results of metallographic studies and laboratory comparative adhesion strength tests of the coating with the base and abrasive wear by Brinell–Havorth method of weld powder coatings on nickel base with a width of weld layer of 20–80 mm and a height of 3–9 mm in one pass and samples of 40Kh steel have been presented. The adhesion strength of coating with hardness of 38–42 HRC was 400–480 MPa. It has been revealed that, at a hardness of the weld layer of 58–61 HRC, the wear resistance of coatings is higher than that of 40Kh steel in normalized and the improved state by 10 and 4.6 times respectively.

Modelling of High Pressure Torsion using FEM

Abstract High Pressure Torsion (HPT) is historically the first and is currently most common process of the severe plastic deformation (SPD). HPT is used for producing nanocrystalline structures in metals and alloys, as well as for cold welding of powders. The result of the HPT treatment is determined by the flow kinematics and the stress state of a material under deformation. P. Bridgman proposed a simple model for the initial assessment of shear strain in the sample during HPT. A number of recent investigations show that the true plastic flow during HPT can differ significantly from the simple model. We present in our report results of the FEM investigation of different types of flow during HPT. We propose a hypothesis that the vortex formation during the SPD process is caused by the local blocking of simple shear in a material under deformation.

Laser powder weld reconditioning of gas turbine engine blades

The paper presents an analysis of technologies of weld reconditioning of gas turbine engine blades made of heat-resistant nickel alloys. The analysis shows that the most prevalent techniques of repair do not meet the demands of modern efficient production. An automated laser cladding machine adapted for fine cladding of blade elements of high-pressure turbines, low-pressure turbines and power turbines of gas turbine units during repairing is proposed within the framework of a joint project with an industrial partner. The weld reconditioning technology based on the principles of additive manufacturing makes it possible to reduce both the losses of material during the subsequent machining and the duration of the latter. Experimental studies on laser cladding showed that the productivity of the cladding process could be up to several tens of working blades per hour. Metallographic studies showe that the deposited layers do not contain macroscopic defects. The results obtained by the authors allow predicting high productivity of the equipment for weld reconditioning, providing high quality of the material deposited.

Synthesis of Nano-Size AlN Powders by Carbothermal Reduction from Plasma-Assisted Ball Milling Precursor**supported by National Natural Science Foundation of China (No. 51177008)

Nano-size aluminum nitride (AlN) powders have been successfully synthesized with a high efficiency method through annealing from milling assisted by discharge plasma (p-milling) alumina (Al2O3) precursors. The characterization of the p-milling Al2O3 powders and the synthesized AlN are investigated. Compared to conventional ball milling (c-milling), it can be found that the precursors by p-milling have a finer grain size with a higher specific surface area, which lead to a faster reaction efficiency and higher conversion to AlN at lower temperatures. The activation energy of p-milling Al2O3 is found to be 371.5 kJ/mol, a value that is much less than the reported value of the unmilled and the conventional milled Al2O3. Meanwhile, the synthesized AlN powders have unique features, such as an irregular lamp-like morphology with uniform particle distribution and fine average particle size. The results are attributed to the unique synergistic effect of p-milling, which is the effect of deformation, fracture, and cold welding of Al2O3 powders resulting from ball milling, that will be enhanced due to the introduction of discharge plasma.

Influence of spark plasma sintering conditions on the sintering and functional properties of an ultra-fine grained 316L stainless steel obtained from ball-milled powder

In this work, 316L samples with submicrometric grain size were sintered by spark plasma sintering. To this aim, 316L powder was first ball-milled with different conditions to obtain nanostructured powder. The process control agent quantity and milling time were varied to check their influence on the crystallite size of milled powder. Samples were then sintered by spark plasma sintering using different sets of sintering parameters (temperature, dwell time and pressure). For each sample, grain size and density were systematically measured in order to investigate the influence of the sintering process on these two key microstructure parameters. Results show that suitable ball-milling and subsequent sintering can be employed to obtain austenitic stainless steel samples with grain sizes in the nanometer range with porosity lower than 3%. However, ball-milling and subsequent sintering enhance chromium carbides formation at the sample surface in addition to intragranular and intergranular oxides in the sample as revealed by X-ray diffraction and transmission electron microscopy. It has been shown that using Boron nitride together with graphite foils to protect the mold from powder welding prevent such carbide formation. For mechanical properties, results show that the grain size refinement strongly increases the hardness of the samples without deviation from Hall-Petch relationship despite the oxides formation. For corrosion resistance, grain sizes lower than a few micrometers involve a strong decrease in the pitting potential and a strong increase in passivation current. As a consequence, spark plasma sintering can be considered as a promising tool for ultra-fine grained austenitic stainless steel.

Проектирование и технология изготовления модернизированной установки для сверхзвуковой газопорошковой наплавки

The results of the device original design development for supersonic gas powder weld deposition (SGP-weld deposition) are presented. The models of basic parts of equipment are considered. The basic requirements made to the device developed are described. The techniques for manufacturing main parts of an updated plant are shown.

On the Principles of the Additive Technology Implementation of Composite Magnetic Coating’s Formation on Non-Magnetic Substrates by Laser Welding of Micro Powders

The article discusses the formation of coatings with magnetic properties on non-magnetic substrates by the method of additive technology of metal powders using high power pulsed laser radiation. An instrumental base for the development of methods for creating local magnetic zones of a given configuration has been described. Approaches to create methods of additive welding of solid solution magnetic zones on the basis of micro-powders of metal alloys have been developed. The coatings with soft magnetic properties on the basis of powders of bronze and iron-containing "Inconel" alloy on non-magnetic substrates were obtained by laser welding. The structural inhomogeneity at the interface of the substrate and the solid solution were studied. Data on hardness and magnetic properties were obtained for formed magnetically soft materials.

Structure of the Steel Surface-Alloyed with Titanium, Vanadium and Carbon in the Process of Powder Welding by a High-Energy Electron Beam

Structural investigations of steel surface layers alloyed with vanadium, titanium and graphite were carried out using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis methods. Coatings were obtained by high-energy electron beam treatment. The titanium – vanadium ratio in initial powder mixtures was as 2:1, 1:1 and 1:2. TiC, a-Fe (ferrite), eutectic consisted of VC and a-Fe were the main structural components of the coating: With an increase of vanadium content shapeless TiC particles turned into dendritic; tertiary dendritic arms consisted of VC. In addition, it also resulted in an increase of carbide particle sizes. The volume fraction of strengthening particles in all coatings was approximately identical (18 %).

Invited: Large-Scale Production and Assembly of Nanowires for the Fabrication of Highly Efficient Thermoelctrics

Energy usage in the United States is predicted to increase exponentially over the foreseeable future. However, data from the Energy Information Administration (EIA) indicates that 56-57% of all energy produced each year in the US is still rejected as waste heat. For example, a major portion of the energy generated by burning gasoline in automobiles (approximately 70%) is lost either in the engine coolant or through the exhaust. Therefore, a possible pathway for meeting the ever-increasing demand for energy is through the recovery of waste heat. Solid-state thermoelectric modules are useful for this purpose. The lack of any moving parts, portability, very long operational lifetimes, and minimal maintenance requirements of these solid-state thermoelectric modules make them very attractive for waste heat recovery. Current state-of-the-art thermoelectric modules are not highly efficient. This limits their use to specialty application (e.g., for powering up satellites). The lack of a pathway for precisely and independently tuning the thermal and electrical transport through materials employed in the fabrication of thermoelectrics is the primary reason for their low efficiencies. Recent theoretical and experimental studies have indicated that nanostructuring of materials serves as a route for independently tuning the thermal and electrical transport through them, and further enhance their heat-to-electricity conversion efficiencies. Of all the forms of nanomaterials, nanowires hold the most promise for the fabrication of efficient thermoelectric modules. The two different dimensions of the nanowires, namely the diameter and the length, offer a convenient pathway for independently tuning the electrical and thermal transport through them. This fact is supported by a few recent experimental studies on individual nanowires that indicated that nanowire form of materials exhibit enhanced thermoelectric performance, compared to their bulk counterparts. As the large-scale deployment of thermoelectrics for terrestrial use is a bulk application, it is required to ensure that enhanced thermoelectric performance observed in individual nanowires is also extendable to assemblies composed of a multitude of nanowires. This further requires strategies for the synthesis and assembly of nanowire powders on an industrial scale. Furthermore, any assembly strategy developed should offer the ability to tune the thermal and electrical transport through the interfaces between the nanowires. In short, the fabrication of next-generation, highly-efficient thermoelectrics requires the large-scale synthesis and interface-engineered assembly of nanowires (1-3). The aim of this presentation is to showcase the progress that has been made in this research area by our group. More specifically, the strategies useful for the bulk production of nanowire powders and their in-situ functionalization with organic molecules (1), together with the strategies useful for assembling them in an interface-engineered manner on a large-scale into functional thermoelectric devices (2,3), will be addressed in this talk (Figure 1). Example illustrations of how the interface-engineered assembly affords thermal and electrical transport control of the interface between the nanowires in the assembly will be presented. Novel strategies for imparting the nanowires resistance against air-, moisture- and acid-assisted degradation will also be presented. Specific examples that will be addressed include the fabrication and characterization thermoelectric devices based on bulk assembled Zn3P2 and ZnO nanowire powders (2,3). In addition, use of phase transformation as a strategy for the simultaneous synthesis (4) and assembly via welding of metal silicide nanowire powders will also be presented. The thermoelectric performance of metal silicide nanowire assemblies will be discussed.ACKNOWLEDGEMENTS Financial support from NSF/DOE thermoelectrics Partnership (NSF CBET # 1048702) is gratefully acknowledged. REFERENCESL. Brockway, M. Van Laer, Y. Kang, S. Vaddiraju, Physical Chemistry Chemical Physics, 15, 6260-6267, (2013).L. Brockway, V. Vasiraju, S. Vaddiraju, Nanotechnology, 25, 125402 (2014).L. Brockway, V. Vasiraju, H. Asayesh-Ardakani, R. Shahbazian-Yassar, S. Vaddiraju, Nanotechnology, 25, 145401 (2014).Y. Kang, L. Brockway, S. Vaddiraju, Materials Letters, 100, 106-110 (2013).

Main thermophysical processes in laser beam buildup welding of metal powders

The energy balance of laser beam buildup welding of powders is analyzed. Comparison of the obtained results with the experimental data shows that a significant portion of the absorbed power of the laser beam is consumed for evaporation the of powder. A procedure of selection and optimization of laser beam buildup of powder is proposed. It is established that the thermal conductivity and thermal diffusivity of powder can increase significantly within its melting owing to subsequent formation of thermal contact between the melt and underlying layer of powder particles. The range of the Peclet numbers corresponding to high efficiency of laser beam buildup welding of powders is determined.

Influence of carbide phase distribution on deterioration of composite coating WOKA PTA-6040 after plasma powder surfacing

The paper presents results of research on abrasive wear of the coating WOKA PTA-6040 formed by plasma powder welding with arc currents 70A, 85A and 100A. Some patterns of wear of the deposited material due to the peculiarities of distribution in it of carbide phase at various currents of plasma arc are identified. The changes of the microstructure, the height of the elemental composition of the deposited layer, as well as sedimentation process of carbides are underlined and their effect on the wear resistance of the deposited material is shown.

Explosive Metalworking: Experimental and Numerical Modeling Aspects

The application of the High Energy Rate Forming (HERF) represents a new paradigm in the field of production of knowledge-based more components materials: furthermore, joining by plastic deformation of the materials is carried out directly, by high speed, high energy shock waves, without using energy transforming equipment as hydraulic presses etc. The energy sources of the HERF processes are either the electrical energy stored in capacitors or chemical energy stored in the high explosives. High explosives can be utilized for many metalworking techniques; however the three main types of explosive metalworking are: Explosive welding and cladding Explosive tubeforming Explosive compaction of powders and granulates. The present work briefly introduces the principles and practices of the three main types of the explosive metalworking techniques mentioned above and discusses aspects of their numerical simulation.

Fabrication of Ni-Base ODS Alloys via Reactive Ball Milling

By the use of YH2 and NiO, oxide particles were introduced in Ni-base ODS alloys through reactive ball milling, which shows the advantages of energy-saving and uniform distribution of the oxide dispersion. The mophological and size evolution of ball milled powder were investigated, and the synthesized oxides were characterized. The results shows that the ball milled powder exhibits the feather of severe deformation. The disintegration of particles occurs after 10 h, and the balance of powder welding and fracturing is achieved around 25 h. the formation of Y2O3 with the size of 20~50 nm was confirmed by XRD and TEM results.

산업용 폭약을 이용한 폭발용접, 폭발성형과 충격분말고화에 관한 실험 및 수치해석적 연구

본 논문은 폭약의 폭발현상을 이용한 폭발용접, 폭발성형과 충격분말고화기술의 기본적 원리와 실험방법, 실험결과에 대하여 기술한다. 타이타늄(Ti)과 스테인레스 강(Stainless steel, SUS 304) 판재의 폭발용접 실험결과, 두 재료 접촉면의 단면에서는 연속적인 젯(jet)모양의 파형이 관찰되었고, 두 금속판재의 설치 경사각도가 <TEX>$15{\sim}20^{\circ}$</TEX> 이고 접착속도가 2,100~2,800 m/s인 경우에 최적의 접합조건을 보였다. 알루미늄(Al) 판재를 이용한 폭발성형 실험과 전형적인 가압성형 실험 결과를 비교분석하여, 폭발성형의 경우가 큰 곡률변형을 보여 가공성이 우수한 것으로 확인되었다. 끝으로 금속과 세라믹의 혼합분말(<TEX>$Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$</TEX>)에 대한 충격고화 실험법을 제안하고 실험을 수행한 결과, 고화체의 표면과 내부에 균열이 확인되지 않았으며 세라믹입자와 금속입자들의 강한 미세조직 결합이 형성되었다. 또한 충격분말고화실험에서 발생되는 폭약의 폭발에 의한 폭굉파와 수중 충격파의 전파 및 간섭현상을 분석하기 위하여 LS-Dyna 3D를 이용한 동적해석을 수행하였다. 그 결과, 물용기 내 벽면에서 반사된 수중충격파가 중앙부에서 중첩되어 폭약의 폭발압력보다 높은 20 GPa의 수중 충격압을 보여, 물용기 내부형상의 중요성을 입증하였다. Theoretical backgrounds on the experimental methods of explosive welding, explosive forming and shock consolidation of powders are introduced. Explosive welding experiments of titanium (Ti) and stainless steel (SUS 304) plate were carried out. It was revealed that a series of waves of metal jet are generated in the contact surface between both materials; and that the optimal collision velocity and collision angle is about 2,100~2,800 m/s and <TEX>$15{\sim}20^{\circ}$</TEX>, respectively. Also, explosive forming experiments of Al plate were performed and compared to a conventional press forming method. The results confirmed that the shock-loaded Al plate has a larger curvature deformation than those made using conventional press forming. For shock consolidation of powders, the propagation behaviors of a detonation wave and underwater shock wave generated by explosion of an explosive are investigated by means of numerical calculation. The results revealed that the generation and convergence of reflected waves occur at the wall and center position of water column, and also the peak pressure of the converged reflected waves was 20 GPa which exceeds the detonation pressure. As results from the consolidation experiments of metal/ceramic powders (<TEX>$Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$</TEX>), shock-consolidated <TEX>$Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$</TEX> bulk without cracks was successfully obtained by adapting the suggested water container and strong bonding between powder particles was confirmed through microscopic observations.