Material Deposition Rate Research Articles

Formation of thick electrical discharge coatings

Abstract Thick electrical discharge coatings, also known by the commercial name “MSCoating”, can be applied on complex shapes and cavities to repair components or act as protective coatings. A variant of the EDM process, it can be used to make coatings up to several mm thickness on electrically conductive substrates. In this paper, an insight into the microstructure and formation mechanism is made through the production of experimental coatings using sacrificial Stellite 31 electrodes on stainless steel substrates. The coatings comprised mostly of ‘splats’ of CoCr. In addition, a significant amount of directly deposited un-melted electrode material was present, along with regions of oxide splats and substantial porosity. Using single discharge analysis, individual deposits contained both melted and un-melted electrode material. Through analysis of the debris, it was found that electrode material either formed spherical particles through melting and resolidification within the discharge gap, or in the form of original unmelted electrode material. It is thought that the low peak pulse section of the current waveform results in increased melting and solidification of material within the discharge gap and on the workpiece. The high peak pulse section of the waveform results in increased mechanical pull-out from the electrode, a proportion of which attaches to the workpiece. The ratio between the peak pulses was found to affect the amount of energy per unit volume of coating material for re-melting. The process is then followed by several discharges preferentially located in the spark region resulting in coating consolidation and build-up through further deposition and re-melting of material. Clustering of discharges was found to be critical in coating formation, where such areas exhibited increased deposition of electrode material. Under the conditions used in the study, the threshold for electrode particle size was found to be between 45 and 70 μm, suggesting that powder diameter is fundamental to thick coating formation. The density of debris within the discharge gap, dependant on the Duty Factor, is thought to correlate with the rate of material deposition from electrode to substrate, where an ideal density of debris produces a large amount of uncontrolled and preferential sparking/arcing, enhancing depositon and attachment.

Effect of dynamic wire feeding on deposition quality in laser cladding process

Laser based material deposition has matured into a well-established industrial technique for precise coating deposition (cladding) and additive layer manufacturing (direct laser metal deposition). Laser cladding is one of the techniques for enhancing the surface performance, hence extending the lifetime of many components in severe corrosive-wear environments. Laser cladding with wire consists in feeding the deposited material as a metallic wire, which is melted by a laser source and manipulated over the deposition volume. This process shows some advantages over powder-based systems such as cleaner processing environment, reduced environmental cost for producing the wire, better surface finishing, and a higher material deposition rate. By means of innovative equipment such as dedicated nozzle and wire feeder systems, well-customized manufacturing strategies can improve the coating quality. Among recent innovations, the change of the wire direction results in a forward final feeding speed. This type of feeding is called dynamic feeding. The controlled movement of the wire is well-known in arc welding, and its synchronization with the arc's electrical parameters gives a drastic increase in stability and controllability. Based on that, the present paper addresses a characterization analysis of the frequency of dynamic feeding process in laser cladding in terms of coating quality. In addition, a dynamic feeding equipment was developed with total flexibility of parameters regulation. Dynamic feeding oscillation showed good stability and lower dilution compared to the conventional method.

Patterning of biomaterials by aerosol jet printing: A parametric study

Bioprinting is an emerging field with ongoing interest in the development of new techniques for structuring and patterning biomaterials in different configurations. Two-dimensional patterning techniques such as micro-contact or inkjet printing enable in vitro studies to investigate the effect of spatial organization on cell physiology. However, micro-contact printing requires relatively lengthy preparation times, while inkjet printing subject materials to significant shear forces and the resolution is limited to approximately 50 ​μm in practice. Aerosol jet printing (AJP) is a versatile, direct-write technique capable of high-resolution deposition of biological materials for cell patterning. However, the resolution and print quality are heavily influenced by a range of different printing parameters. This systematic study investigates the influence of critical printing parameters, using aqueous gelatin as a model biomaterial ink. Our results indicate that the tested parameters influence the line quality by inducing a change in one or more of the following primary processes: material deposition rate, evaporation rate and the aerosol jet focusing. Furthermore, with minimal adjustments to parameter settings, gelatin lines could be printed with a width of 30 ​μm. A systematic approach is outlined for the selection of suitable parameters for stable and accurate printing at a desired resolution. This provides a framework for approaching the optimization of parameters for novel combinations of biomaterial inks and substrates. An improved understanding of the complex interplay between different process parameters is expected to support the development of new applications of aerosol jet printing in biology.

Experimental investigation of tungsten and copper carbide coating on AISI 1020 steel using electro discharge coating process

This paper elaborates about the material deposition rate (MDR) processed by electro discharge coating (EDC). Powder metallurgy (PM) route was considered for preparation of tool electrodes are in different proportions of W-Cu for the EDC process. The substrate material was of AISI 1020 steel. The experiments were carried out using Electric discharge machining (EDM). The process parameters were considered as peak current, pulse on time and compositions in different proportions of tungsten and copper (W-Cu) based on preliminary experiments. The optimization of the process was done by using Taguchi technique. A total of L16 orthogonal array was considered for experimentation. The Taguchi analysis was done to identify the importance of the levels and optimal parameters for the electro discharge coating. The significance of the process parameters was tested using Analysis of variance (ANOVA) conducted at 95% confidence level. The peak current and pulse duration effect on the material deposition rate is evaluated. The experimental results shows that peak current and pulse duration has important role on the performance of the coating within the processing range. The microstructure of the specimen was done by Scanning electron microscope (SEM) to recognize the presence of W-Cu coating on the substrate surface.

Influence of inductive heating on coating geometry during deposition of AISI 316 stainless steel over EN8 carbon steel using friction surfacing process

The present experimental work has attempted to analyze the influence of substrate heating on coating geometry during the deposition of stainless steel over medium carbon steel substrate using friction surfacing process. Inductive heating was applied to the substrate plate using an electric unit with three different temperatures of 200 °C, 400 °C, and 600 °C. Elemental process parameters like axial force, rotational speed and transverse speed with different combinations were considered for conducting experimental work. The material consumption rate (CR) and deposition rate (DR) were extensively studied. The high rate of material consumption and deposition were seen at samples obtained from 600 °C of inductive heating compared to the conventional friction surfacing process. Using the IR thermometer, the interface temperature at both the advancing and the retreating side was recorded which showed a higher temperature was experienced by advancing side than the retreating side. The mechanical strength of the coating was analyzed by micro hardness and bending tests. Interfacial attributes of the coating were analyzed by using FE- SEM images and the elemental composition at the coating interface was studied through the EDAX report.

Multi-criteria environmental and economic impact assessment of wire arc additive manufacturing

Wire Arc Additive Manufacturing (WAAM) is a fusion- and wire-based additive manufacturing technology which has gained industrial interest for the production of medium-to-large components with high material deposition rates. However, in-depth studies on performance indicators that incorporate economic and environmental sustainability still have to be carried out. The first aim of the paper has been to quantify the performance metrics of WAAM-based manufacturing approaches, while varying the size and the deposited material of the component. The second aim has been to propose a multi-criteria decision-analysis mapping to compare the combined impacts of products manufactured by means of the WAAM-based approach and machining.

Mechanical Finishing of Wire Arc Additive Manufactured Aluminum Parts

Additive Manufacturing (AM) processes enable new design freedoms in engineering. Due to that, the use of AM offers the potential to shorten time to market and to reduce either manufacturing cost or material waste. Furthermore, parts can be individualized by using AM and product properties can be modified selectively. Hence the Wire Arc Additive Manufacturing (WAAM) process is utilized in order to minimize the energy consumption in a process chain of automotive components. WAAM is selected due to its high material deposition rates and its comparably low costs. The WAAM process is used to attach part features onto semifinished products in order to adapt the parts to the expected loads. To meet the requirements regarding geometry and surface quality, the welded part features must be finished mechanically afterwards by milling. The influence of mechanical finishing on the surface integrity of WAAM parts are not yet investigated sufficient. Further research regarding the mechanical finishing of additive manufactured structures and its influence on the resulting material properties is required. The influence of milling and deep rolling on the surface integrity of AlSi12 parts produced by WAAM is investigated and the results are presented. This study especially focuses on the effect of deep rolling on the surface integrity, hardness, microstructure and mechanical properties of the parts. As a result of this paper, the improvement of the surface integrity of WAAM parts subjected to deep rolling is verified.

Microstructure study on electro discharge deposited magnesium alloy with semi sintered and sintered electrode

In this research, electro discharge deposited ZE41A magnesium alloy with semi sintered and sintered electrode are studied. Parameters used in this study were compaction load, current and pulse on time and coating responses were material deposition rate (MDR), micro hardness (MH). For the electrical discharge coating (EDC), electrodes were prepared using tungsten carbide and copper powder by powder metallurgy method. It was observed that the MDR and MH increased when increased current and pulse on time in low compaction load for semi sintered and sintered electrode. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were analysed in the deposited surface to study the microstructure and presence of electrode materials respectively. Comparative microstructure study on electrical discharge coating of ZE41A magnesium alloy with powder metallurgy semi sintered and sintered electrode was carried. Among two conditioned electrode, semi sintered electrode has the higher material deposition rate and micro hardness. Further increased the sintering temperature the deposition is formed with the large cracks and craters.

Heat transfer analysis of automated fiber placement of thermoplastic composites using a hot gas torch

With more and more use of composites in engineering applications, the need for automated composites manufacturing is evident. The use of automated fiber placement (AFP) machine for the manufacturing of thermoplastic composites is under rapid development. In this technique, a moving heat source (hot gas torch, laser, or heat lamp) is melting the thermoplastic composite tape and consolidation occurs in situ. Due to the rapid heating and cooling of the material, there are many issues to be addressed. First is the development of the temperature distribution in different directions which gives rise to temperature gradients. Second is the quality of the bond between different layers, and third is the rate of material deposition to satisfy industrial demand. This paper addresses the first issue. The temperature distribution affects the variation in crystallinity, and residual stresses throughout the structure as it is being built. The result is the distortion of the composite laminate even during the process. In order to address this problem, first the temperature distribution due to a moving heat source needs to be determined. From the temperature distribution, the development and distribution of crystallinity, residual stresses and deformation of the structure can then be determined. As the first phase of the work, this paper investigates the temperature distribution due to a moving heat source for thermoplastic composites, without considering the material deposition. A finite difference (FD) code based on energy balance approach is developed to predict the temperature distribution during the process. Unidirectional composite strips are manufactured using AFP and fast-response K-type thermocouples (response time of 0.08 s, as compared to normal thermocouples with response time of 0.5 s) are used to determine the thermal profiles in various locations through the thickness of the composite laminate subjected to a moving heat source. It is shown that temperature variations measured experimentally during the heating pass, using thermocouples embedded into the composite substrate, underneath layers of the composite material, are consistent with the generated thermal profiles from the numerical model. The temperature distribution, in both the direction of the tape and through-thickness direction can be predicted numerically.

Production of hard and lubricating surfaces on miniature components through micro-EDM process

The study acclaims the generation of hard, wear-resistant, and lubricating layer on Ti alloy using molybdenum disulfide (MoS2) powders mixed in dielectric (deionized water) using a brass tool electrode (diameter 800 μm) through the micro-electrical discharge process. The deposition rate, micro-hardness, recast layer, and surface roughness were studied for the surface generated through the process and correlated with the XRD, AFM, electron probe micro-analyzer, EDS analysis, and FESEM images. Results indicate that a higher voltage (60 V) and powder concentration (12 g/L) increase the material deposition rate in the form of intermetallic compounds deposited on the recast layer. The coated layer formed shows an increase in micro-hardness ranging from 426.42 to 714.25 HV, which is more when compared to the base material hardness of 417.61 HV. In addition to this, lower micro-cracks were seen at high powder concentration, voltage, and duty factor with improved surface quality. The pin-on-disc wear test of the coated samples was performed, and results indicated that the specific wear rate decreased with the increase in duty factor due to the formation of hard and wear-resistant intermetallic compounds as confirmed from the EDS and XRD plots.

Residual stress in metal arc additive manufacturing of mill knives cutting edges

The additive manufacture process by electric arc is growing in importance due to its high material deposition rate and application in large components. However, the process also has its limitations regarding the poor quality of the surface finish and the generation of residual stresses that require post-processing for improvements. This work investigates the metal arc additive manufacturing of mill knives cutting edges with the coated electrode DIN 8555 E6-UM-60-S and substrate material, the AISI 1020 steel. In this scenario, the effect on the change of the material deposition direction (longitudinal and transverse direction to sample length) in the residual stresses of the specimens is investigated. The following additional analyses were carried out: temperature behavior on the substrate during deposition and analysis of the microstructure in the material deposition region. The maximum average temperature in the specimens during the longitudinal deposition was 301 °C and, in the transverse, 347 °C. The longitudinal deposition resulted in lower values of residual stresses in relation to transverse deposition (difference of − 62.4 MPa at compression stress and 69.3 MPa at tensile stress).

Layer‐by‐Layer Formation of Polyamine‐Salt Aggregate/Polyelectrolyte Multilayers. Loading and Controlled Release of Probe Molecules from Self‐Assembled Supramolecular Networks

AbstractThe use of soft materials as building blocks in layer‐by‐layer (LbL) assemblies represent a very appealing and useful approach to enhance the loading capacity of thin films. Here, the capacity of positively charged polyamine‐salt aggregates (PSAs) based on ionically crosslinked poly(allylamine hydrochloride) (PAH) with phosphate anions (Pi) is explored to act as building blocks in construction of multilayers by alternated deposition with poly(sodium 4‐styrenesulfonate). Hybrid thin films are successfully prepared by the LbL technique with a highly regular growth and a material deposition rate higher than the traditional full polyelectrolyte LbL. The loading of bromophenol blue (BPB) is evaluated by integration into PSAs followed by LbL deposition and monitored with UV–vis spectroscopy. Finally, the release of the dye molecules is carried out by exposing the film to different aqueous solutions. It is shown that a fully controlled release can be achieved by simply varying the media pH obtaining total BPB release over periods between minutes and months. The data obtained reveal that this new LbL construction strategy using ionically crosslinked PAH/Pi colloids allows to obtain nanoarchitectures with high loading capacity and remarkable properties for controlled release.

Effects of the Nozzle Tip Clogging and the Scanning Direction on the Deposition Process During Laser Metal Deposition of Alloy 718 Using a Four-Stream Discrete Nozzle

Depending on the configuration of the LMD system, the nozzle tilting is necessary to be able to manufacture parts with complex geometry. In these cases, the use of discrete coaxial nozzles is recommended. With this type of nozzle, the powder can clog the internal tips of the nozzle streams due to an inappropriate shape, size distribution, humidity or temperature conditions of the powder particles during the deposition process. This undesired effect can be an opportunity depending on the combination of the activated powder tips for coating complex surfaces when the geometry of the substrate acts as a barrier for the powder stream.This work presents for first time the effect of the scanning direction and the stream clogging on the deposition process in terms of powder efficiency, Material Deposition Rate (MDR) and clad geometry and dimensions, when Alloy 718 is deposited by LMD using a four-stream discrete coaxial nozzle.

A nonlinear coupled-variables model for mass transfer modes in MIG-MAG processes with experimental validation

Welding processes have relevant importance in many areas of industry, especially in the manufacturing area. The choice of mass transfer mode, to weld metal plates, depends on workpiece structure and its sensibility to the heat input and necessity for material deposition rate. Then, aiming at the mass transfer modes in metal inert gas-metal active gas (MIG-MAG) processes utilising pure CO2 as shielding gas, the objective of this paper is to present a detailed mathematical modelling for globular and short-circuit transfer modes. The proposed models cover a large set of process dynamics, approximating the simulated dynamics very closely to the physical process, which give a high level of credibility for the models. Furthermore, simulations and experimental data are presented to corroborate the validation of both models.

A nonlinear coupled-variables model for mass transfer modes in MIG-MAG processes with experimental validation

Welding processes have relevant importance in many areas of industry, especially in the manufacturing area. The choice of mass transfer mode, to weld metal plates, depends on workpiece structure and its sensibility to the heat input and necessity for material deposition rate. Then, aiming at the mass transfer modes in metal inert gas-metal active gas (MIG-MAG) processes utilising pure CO2 as shielding gas, the objective of this paper is to present a detailed mathematical modelling for globular and short-circuit transfer modes. The proposed models cover a large set of process dynamics, approximating the simulated dynamics very closely to the physical process, which give a high level of credibility for the models. Furthermore, simulations and experimental data are presented to corroborate the validation of both models.

Surface modification of Ti-alloy by micro-electrical discharge process using tungsten disulphide powder suspension

This work aims to produce a hard and solid-lubricating layer over Ti6Al4V work piece surface through μ-EDM process. Deionised water mixed with tungsten disulphide (WS2) powder (average particle size: 15 μm) was used as dielectric medium and brass rod of diameter 800 μm was used as the tool. Various responses such as micro-hardness (HV), recast layer thickness (RLT), material deposition rate (MDR), and surface roughness (SR) were measured and correlated with FESEM images, EDS, XRD and EPMA results. The results indicated the formation of various intermetallic compounds on the modified surface. A higher MDR (0.049 mm3/min) was found at maximum powder content of 12 g/L. There is an improvement in micro-hardness from 421.38 HV to 881.34 HV when compared to that of the base material (417.61 HV). Maximum recast layer thickness of 13.11 μm was obtained at parameter settings of 12 g/L, 60 V and 70% duty factor. Wear test was performed and found that the specific wear rate is decreased as compared to that of the base material.

Wire and arc additive manufacturing: a comparison between CMT and TopTIG processes applied to stainless steel

Wire and arc additive manufacturing (WAAM) enables the building of near net-shape components layer by layer by using arc welding technologies and wire filler metal as feedstock. The study aims at comparing the applicability of two innovative robotic arc welding technologies (cold metal transfer (CMT) and TopTIG) for additive manufacturing (AM) of stainless steel parts. Initially, a process development has been completed with the goal of optimizing material deposition rate during arc time. Both continuous and pulsed current programs were implemented. Then, different thick-walled samples composed of more than one overlapped weld bead per layer were manufactured in 316L stainless steel grade by CMT and TopTIG. Mechanical properties have been determined in as-build samples in different building orientations. WAAM applying CMT and TopTIG welding technologies is analyzed in terms of part quality (defined as the absence of defects such as pores, cracks, and/or lack of fusion defects); surface finishing; part accuracy; productivity; microstructural characteristics; and mechanical properties. Achieved mechanical properties and deposition rates are compared with the state of the art. Findings and conclusions of this work are applicable to the industrial manufacturing of stainless steel parts and requirements to apply these technologies to other expensive materials are finally discussed.

Prediction of the Fiber Orientation State and the Resulting Structural and Thermal Properties of Fiber Reinforced Additive Manufactured Composites Fabricated Using the Big Area Additive Manufacturing Process

Recent advances in Fused Filament Fabrication (FFF) include large material deposition rates and the addition of chopped carbon fibers to the filament feedstock. During processing, the flow field within the polymer melt orients the fiber suspension, which is important to quantify as the underlying fiber orientation influences the mechanical and thermal properties. This paper investigates the correlation between processing conditions and the resulting locally varying thermal-structural properties that dictate both the final part performance and part dimensionality. The flow domain includes both the confined and unconfined flow indicative of the extruder nozzle within the FFF deposition process. The resulting orientation is obtained through two different isotropic rotary diffusion models, the model by Folgar and Tucker and that of Wang et al., and a comparison is made to demonstrate the sensitivity of the deposited bead’s spatially varying orientation as well as the final processed part’s thermal-structural performance. The results indicate the sensitivity of the final part behavior is quite sensitive to the choice of the slowness parameter in the Wang et al. model. Results also show the need, albeit less than that of the choice of fiber interaction model, to include the extrudate swell and deposition within the flow domain.

On the Simulation Scalability of Predicting Residual Stress and Distortion in Selective Laser Melting

Rapid heating and cooling thermal cycle of metals in selective laser melting (SLM) generates high tensile residual stress which leads to part distortion. However, how to fast and accurately predict residual stress and the resulted part distortion remains a critical issue. It is not practical to simulate every single laser scan to build up a functional part due to the exceedingly high computational cost. Therefore, scaling up the material deposition rate via increasing heat source dimension and layer thickness would dramatically reduce the computational cost. In this study, a multiscale scalable modeling approach has been developed to enable fast prediction of part distortion and residual stress. Case studies on residual stress and distortion of the L-shaped bar and the bridge structure were presented via the deposition scalability and validation with the experimental data. High residual stress gradient in the building direction was found from high tensile on the surface to high compressive in the core. The part distortion can be predicted with reasonable accuracy when the block thickness is scaled up by 50 times the layer thickness from 30 μm to 1500 μm. The influence of laser scanning strategy on residual stress distribution and distortion magnitude of the bridges has shown that orthogonal scanning pattern between two neighboring block layers is beneficial for reducing part distortion.

Recent developments in turbomachinery component materials and manufacturing challenges for aero engine applications

In the recent years the development of turbomachinery materials performance enhancement plays a vital role especially in aircraft air breathing engines like turbojet engine, turboprop engine, turboshaft engine and turbofan engines. Especially the transonic flow engines required highly sophisticated materials where it can sustain the entire thrust which can create by the engine. The main objective of this paper is to give an overview of the present cost-effective and technological capabilities process for turbomachinery component materials. Especially the main focus is given to study the Electro physical, Photonic additive removal process and Electro chemical process for turbomachinery parts manufacture. The aeronautical propulsion based technologies are reviewed thoroughly where in surface reliability, geometrical precession, and material removal and highly strengthened composite material deposition rates usually difficult to cut dedicated steels, Titanium and Nickel based alloys. In this paper the past aeronautical and propulsion mechanical based manufacturing technologies, current sophisticated technologies and also future challenging material processing techniques are covered. The paper also focuses on the brief description of turbomachinery components of shaping process and coating in aeromechanical applications.