The EPMA has named the winners of its latest powder metallurgy component awards competition.
The winner of the EPMA Powder Metallurgy Components Award 2018 in the Additive Manufacturing category went to Rosswag GmbH for the ForgeBrid process.
By combining the two production processes of open die forging and selective laser melting, the disadvantages of each process can be circumvented. For this purpose, the respective method is only used in the segment of the part for which it is suitable. A basic body is conventionally forged and subsequently machined to produce a plain surface. On this surface, the functionally optimised contour is added by selective laser melting.
With this innovative production chain, a component is created which consists of one identically material charge and has been produced in a resource-saving manner. Consumption of coolants, lubricants and material is reduced, since the complex geometries aren’t produced with high costs and expenditure of time by machining.
The remnants produced during sawing and forging can be recycled in the AM process. For this purpose, they are converted into a fine-grained metal powder in an atomizing process, melting the metal scrap above the melting point in the crucible. The molten material is atomized from the crucible via a nozzle by means of an inert gas stream to a spray. Subsequently, the spray particles solidify in the drop tower. In a downstream process step, the particles are fractionated for a stable SLM process between 10 mm and 60 mm.
The forging-SLM-Hybrid produced in this way offers a possibility to equip even large-volume parts with features which can only be realized by the AM process. Due to the improved grain structure profile, the forged component area has excellent mechanical-technological properties, especially with regard to the fatigue strength. The complex segments of the part are then manufactured in such a way that an added value results which could not be achieved by conventional production processes.
The hybrid production process is therefore a suitable approach to meet safety requirements and still achieve a functional optimization of the component. Lightweight components in particular can be designed in such a way that the requirements can be met by the use of AM technology.
The EPMA Powder Metallurgy Component Award 2018 in the Hot Isostatic Pressing category went to Framatome/Aubert & Duval for a NNS reactor coolant pump impeller.
Framatome fabricates and supplies reactor coolant pump (RCP) sets covering the nuclear market. In this RCP, a component with large-dimension and complex geometry creates real production difficulties.The manufacturer aims at improving its mechanical performance in connection with the nuclear power plants lifetime extension politics.
Large components with complex shapes such as impellers were traditionally manufactured by casting, but the lifetime of these products was limited by the ageing of the material, due to the presence of ferrite years. In this context, alternative approaches consisting of machining impellers from a forged ingot have appeared in the market place. However, this solution requires the use of a 4000 kg forged ingot to create a 600 kg impeller resulting in 85% of scrap material.
A consortium composed of Framatome, Aubert & Duval, Ventana Group, Metalscan and institutional laboratories (Université de Bourgogne, ARTS and CEA) established the manufacturing sequence of a large-dimension impeller in 316L austenitic stainless steel by means of PM-hip processes with a Near Net Shape (NNS) approach.
The tooling of the impeller was designed by 2D/3D simulation and then machined in low carbon steel elements. Once assembled and welded, the low-carbon steel container is filled with 316L powder and prepared according to classical HIP capsule preparation procedures. After the HIP cycle, a rough machining was performed to open hydraulic channels and then facilitate the chemical pickling. This approach aims at reducing as much as possible the machining and finishing operations after HIP, in particular on the blades of the impeller, to limit the final cost of the part and reduce the fabrication times.
The final part produced exhibited the expected geometric features (+/- 2mm), fine grain size (around 50-micrometres) and isotropic microstructure and excellent mechanical properties, thus validating the global NNS fabrication approach of a large and complex part by PM+HIP. At the end of the project, Framatome considers the PM+HIP NNS impeller as a technical solution, promising an extended lifetime to future customers.
The winner of the EPMA Powder Metallurgy Component Award 2018 in the Metal Injection Molding category went to AMT PTE Limited for a one piece nozzle.
It is an impossible task to produce this product near net shape using other conventional methods. Possible methods would require the brazing of multiple machined components, which would end up with high material wastage and high cost. The MIM One Piece Nozzle produced a good finish with a complex internal channel in a sustainable and economical way. This product has opened up an entirely new application for MIM process capabilities, and definitely the most complex part created by AMT PTE Limited to date.
Development efforts focused on controlling the distortion of the plastic inserts during the MIM process, as high injection pressure and temperature greatly affects the insert integrity. Instead, it is necessary to maintain high packing pressure in the inner core channel, as any loss in pressure will encourage weakness resulting in cracks. Finding the ideal injection parameters that resulted in an overall good part were highly challenging during the development phase. The other critical feature is the tip of the nozzle, the diameter of the hole and gap surrounding it are controlled in micron range, which are MIMed without secondary operations. Looking at the cross-sectioned you will understand how the critical features were achieved with great definition.
The One Piece Nozzle is applied in a Selective Catalytic Reduction (SCR) system for commercial vehicles in Europe to comply with the Euro 5 and Euro 6 standards. Urea is connected to the central hole, and compressed air is connected to the other channel. The compressed air is pumped into the nozzle exiting though the ring at the nozzle tip. This generates a low pressure region at the tip producing a venturi effect which draws out the urea from the middle channel and spray onto the SCR system, which will reduce the exhaust nitrogen oxide to nitrogen gas and water.
The special feature is the undercut internal channel, which can only be produced using AMT’s patented In-Coring technology. No other metal forming process can produce this near net shape with minimal secondary finishing operations, making it specifically designed for the MIM process. The cost savings could be more than 200% if a similar quality and finished part were produced by conventional machining and brazing.
The EPMA Powder Metallurgy Component Award 2018 in the PM Structural category went to Gervorkyan, SRO. for a driving flange.
The Driving Flange was designed in co-operation with one of the leading power tools producers. The part is brand-new and has never been produced before by any other technology. The original conception, including prototypes, was designed for CNC machining from conventional bars. The adaptation to PM technology provided a huge price reduction in comparison to traditional technology.
The new design of the driving flange represents a truly new approach in the cutting and brushing disc clamping action.
It is expected to spread this concept worldwide during the next few years, including complete replacement of the old generation of a flange, which uses an internal thread to create a clamping force. From the end user point of view, the main contribution is the reduction in the time which is needed to replace already worn discs – within a few seconds instead of minutes. The Driving Flange is compacted on CNC hydraulic press using all three upper axes and all four lower axes. To ensure a higher hardness of the surface layer and tough core of the part the case hardening is used. CNC turning is used to ensure precise internal diameter and CNC milling is used to create four counter bars for screws.
Three components were highly commended:
Additive Manufacturing category – University of West Bohemia, Regional Technological Institute, Kraken, Special Light Milling Head
Metal Injection Molding category – Schunk Sintermetalltechnik GmbH, HPC-Vane
PM Structural category – ASCO Sintering Co, Lock Bolt
This story is reprinted from material from the EPMA, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
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