Papers by Keyword: Hybrid Process

Abstract: Pores and weak bonding are the inherently drawbacks for thermally sprayed coating. Laser beam is an attractive approach to remelt thermal spray coating for obtaining fully dense coating with metallurgical bonding with substrate. However, defects of holes or cracks are highly inevitable with unmatching remelting processing parameters. In this work, a thermally sprayed Cr₃C₂-NiCr cermet coating by high velocity oxygen fuel spraying was post-processed by laser remelting with a series of varying beam energy densities from 37.5 J/mm² to 225 J/mm². The defect evolution was investigated by both experimental and numerical simulation methods. Large holes and through-thickness cracks were typical defects observed in the remelt coating by optical microscopy. The experimental results show that remelting-induced defects evolve into three stages with laser energy density. The effect of energy density on remelt structure was further verified with the temperature field by numerical simulation with ABAQUS code. The stress field interpreted the crack formation at periodical formation sites. The results on the defect evolution shed light on obtaining functional coatings for industrial applications.

Abstract: The paper aims to report preliminary researches towards to development of new hybrid welding system by coupling a microwave beam with a TIG torch. The main research was focused on the designing of hybrid system as well as to establish the heating/welding mechanism by coupling two different thermal sources. Therefore, a specific welding chamber was designed taking into consideration the limitations provided by microwave waveguide technical specs, geometrical shape and dimensions of the TIG torch as well as the temperature monitoring during welding process and video surveillance for data recording. A microwave generator with adjustable power from 0 to 1250 W was coupled with a TIG torch and welding power source in order to establish the main parameters for hybrid system. The preliminary researches reported that the MW-TIG hybrid welding could be applied to eutectic joining of materials using low power (up to 600 W) injected from microwave generator as well as low welding current (up to 20 A). The flow of shielding gas have been established initially to 2 l/m. The research related to stabilization of MW-WIG plasma arc have been studied by increasing the flow of shielding gas up to 10 l/m. The results have shown that the microwave generator and TIG torch can be coupled to obtain hybrid-welding process without any matching tuning devices but with risks for damaging the microwave generator. Further researches will be done in order to design auxiliary devices to optimize the hybrid-welding process and to avoid any unwanted plasma arc discharge from welded base materials to microwave generator. In terms of temperature monitoring, an infrared pyrometer has been used. The IR pyrometer was targeted to the base materials in order to be able to measure their temperature without any influences from plasma arc. The results obtained have shown a stable plasma at average microwave power around 400 W even without any TIG current.

Abstract: There have been no breakthroughs in ferrous metallurgy for the last 80 years. Automation and digitalization arrived, while the actual steel making processes saw almost no changes. Today, almost all industries experience rapid changes. In 2018 we will see a launch of trains that can travel as fast as1,200 km/h. In 2022 we will see aircrafts capable of flying from London to New York in 1 hour. They already know how to grow human arms and legs. And driverless taxis have become extremely popular. Should we be expecting to see a major breakthrough in metallurgy any time soon? In this paper you will learn about this and other problems, as well as possible ways to solve them. Also, the paper focuses on the results of the development of theory, mathematical models and novel processes, which were helpful in the forming of the ultra-high strength materials by combining the conventional methods of forming such as stamping, plate rolling, plastic bending and asymmetrical rolling. The ultimate aim was to manufacture parts having complex geometries of ultra-high strength sheets. Metalworking techniques like asymmetrical rolling gave rise to very high shear strains and it was used for increasing the strength of the materials. The addition of the incremental sheet forming to the varied combinations of conventional forming processes was used for increasing in the flexibility of the manufacturing process for ultra-high strength. The results of the research project were also encompassing numerical simulation and experimental investigations of the combined process accompanied by the development of the theoretical models for the same.

Abstract: Cold spray utilizes supersonic jets of compressed gas to accelerate powder particles at high velocities. A coating is formed on a substrate by the impact and deformation of particles. Laser Shock consists in illuminating a sample with a pulsed laser to generate a high pressure shock. Cold spray and laser shock are extremely dynamic processes (time scales of about 10-100 ns). In this paper, applications of laser shock for the study of cold spray are presented. A powder particle of a given size and morphology can be laser shock accelerated at cold spray velocities, finally hitting a substrate in a controlled experimental simulation of the process. Results allow also the characterization of powder materials, through the comparison of deformed particles with numerical impact simulations and the fitting of a plasticity model. Two main advantages compared to the split-Hopkinson pressure bar emerge: deformation rates are closer to cold spray conditions and powders are directly tested, rather than macroscopic cylinders. Laser shock can also be used to measure adhesion and internal cohesion of cold-sprayed coatings (LAser Shock Adhesion Test, LASAT). Cold LAser Shock Spray (CLASS), consisting in laser shocking a coating to re-spray it, can be used to characterize property gradient within a coating or as a new spraying process. Laser shock techniques can prove beneficial for the knowledge of powder materials, which is key for advances in cold spray and other powder based processes. Moreover, the combination of the two techniques could lead to hybrid processes.

Abstract: Multi-pass laser and laser-arc narrow-gap welding make it possible to obtain high-quality butt joints of large-thickness pipe steels with hardness up to 2600...2800 MPa and toughness close to the base metal toughness at a temperature of 20°C. When multi-pass welding methods are used, the subsequent pass makes heat treatment of the previous ones, and reduces the rate of their cooling yet. This allows excluding heat treatment of the joint after welding, which significantly reduces the time and costs for manufacturing large-sized structures.

Abstract: In many respects, the advantages of the hybrid welding process Plasma-MIG are explained by the interaction of the arc discharges, which make up it: a plasma discharge and an arc with a consumable electrode (MIG). Knowledge and understanding of the laws of this interaction is very important for the implementation of the process and obtaining good results. The theoretical analysis of the influence of the plasma discharge temperature with non-consumable electrode on the melting of the electrode wire was carried out. The dynamics of the melting of the electrode wire and dynamics of circuit with consumable electrode arc were been investigation. Estimates of the maximum value of the temperature of plasma discharge have been made. These results were used to select welding modes and for carrying out the technological experiments.

Abstract: ACB (France) and its sister company Cyril Bath (USA) have a long experience in the fields of hydraulic presses and metal forming for the aerospace industry. This experience is particularly focused on the manufacturing of structural and engines parts. The purpose of this presentation is to show how the combination of both activities in the fields of Hot Forming/Sizing and Superplastic Forming results in continual progress and how recent evolution open new fields of applications. First, both processes will be shortly introduced. The advantages of Hot Forming, Superplastic forming and Diffusion Bonding technologies will be demonstrated regarding current customer’s requirements. To conclude an overview of on-going research programs will be made to present strong advantages of dual presses combining Hot Forming and Superplastic processes.

Abstract: Hybrid additive manufacturing technologies combine selective material deposition with a conventional milling process in one machine, enabling the production of complex metal parts and reducing the need for part specific tools. The hybrid technology offers technological advantages compared to more established additive fabrication processes, such as powder bed fusion. Compared to powder bed based additive processes, which are currently in a prevailing positon regarding AM adaption, hybrid additive technologies enable increased build rates, enhanced build volumes and a reduction of machine changes. In the Laser Metal Deposition (LMD) process, metal powder is deposited through a nozzle and melted by a laser on the surface of the part. By integrating the LMD process into a machining center, good surface roughness and low tolerances can be realized by means of e. g. milling without reclamping. In comparison to powder bed based processes, cost and resource input have not been investigated in detail. In this study, hybrid additive manufacturing technologies are analyzed regarding cost and resource input. A cost model for hybrid additive processes is introduced that enables the analysis of the manufacturing cost structure for a given part. Furthermore, the resource inputs for the operation of a hybrid production machine are estimated.

Abstract: The aim of this study is to optimize the process variables of a novel hybrid process of electrical discharge machining (EDM) and abrasive jet machining (AJM) using grey relational analysis. The multi-performance characteristics associated with the developed hybrid process such as the material removal rate (MRR), electrode wear rate (EWR), and surface roughness (SR) were explored through an experimental study according to an L18 orthogonal array based on the Taguchi experimental design method. The experimental results confirmed the multi-performance characteristics of the developed hybrid process would clearly be improved through optimizing the process variables using grey relational analysis.

Abstract: Coking wastewater contains high concentration of refractory and toxic compounds. The effluent quality usually cannot meet the discharge limits after single conventional biological treatment processes. In order to find more effective coking wastewater treatment process, a serious hybrid treatment process were reviewed in this paper, which include: anoxic-anaerobic-oxic(A2/O) combined with membrane bioreactor (MBR); Fe/C micro electrolysis combined with Fenton process. Fenton oxidation combined with biologically process. Wastewater quality and operating parameters were compared. Through this review, we found that hybrid process is more efficiency to treat coking wastewater.