150616 Metal Additive Manufacturing on existing products (Paula Guedes Martins Ferreira)
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150616 Metal Additive Manufacturing on existing products (Paula Guedes Martins Ferreira)
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150616 Metal Additive Manufacturing on existing products (Paula Guedes Martins Ferreira)
- 1. Nationaal Lucht- en Ruimtevaartlaboratorium – National Aerospace Laboratory NLR Metal Additive Manufacturing on existing products NLR Internship SINTAS Project Paula Guedes Martins Ferreira 16/06/2015
- 2. 2 Introduction Objective: Preliminary study on Metal Additive Manufacturing on existing products New possibilities on repair
- 3. 3 SLM Technology Selective Laser Melting (SLM) Selective laser melting of metal powder layer by layer Precise geometry Mechanical properties
- 4. 4 Market Needs Repair of high end products Aero engine components Turbine blades Tools
- 5. 5 Market Needs Repair of high end products Combination with conventional technologies Interface Quality Position Precision
- 6. 6 Literature Study EU projects - RepAIR On-site maintenance and repair Integrated direct digital manufacturing - FANTASIA Additive manufacturing repair techniques Laser Metal Deposition (LMD) and Direct Laser Forming (DLF)
- 7. 7 Choice of Material Inconel 718 High strength Corrosion resistance Excellent welding properties
- 8. 8 SLM Process Different process parameters Specimen matrix 20 different specimen Specimen geometry Hollow cylinders Small structure Surface Plate Optimal Conditions Holes for positioning
- 9. 9 SLM Process – Processing Parameters Choice of parameters do be varied Available time Influence in the interface
- 10. Varying Parameters Laser Power Scan Speed Initial Conditions 10 SLM Process – Processing Parameters Fixed Parameters Heat Treatment Preheating Layer Thickness Laser Focus
- 11. 11 Test and Analysis Tests and Analysis Microstructural analysis Porosity analysis Vickers microhardness test
- 12. 12 Remaining Objectives Remaining Objectives Evaluate the results Describe a procedure Prepare a report
- 13. 13
Editor's Notes
- My name is Paula Guedes, I am a Brazilian student doing a one-year exchange in University of Twente. I am doing a two-month internship at NLR with Marc de Smit and with supervision of Professor Tiedo Tinga. My objective in those two months is to do a preliminary study on additive manufacturing on existing products. This study can help develop new possibilities for repair of parts, using 3D printing on damaged components, what fits the guidelines of the SINTAS project.
- The technology to be used in this project is an additive manufacturing technology known as SLM, Selective Laser Melting. After the CAD file of the product is divided in thin slices, a laser melts metal powder in the exact geometry, slice by slice. This process allows very precise geometries, not obtained by conventional manufacturing, while still maintaining the mechanical properties of the material. My objective is to study the use of this technology on existing parts.
- Using SLM technology on existing products, can lead to advances in the repair of high ends parts, which are seen as non-repairable by conventional manufacturing. This products sometimes are discarded when small damage happens and printing on existing products can allow the repair of this products, by removing the damaged parts and adding new material, following the original geometries. The picture, for example, shows the repair of an aero engine case by the use LMD (Laser Metal Deposition), a related technology.
- Another use of this technology is the combination with conventional technologies, in products that are neither completely fitted for conventional machining nor for additive manufacturing. In this kind of products you could manufacture conventionally part of the product and then print more complex parts on top of it. For both uses, the main challenges is to maintain the interface quality, so that there is a good connection between the existing and the new products, and this will be the focus of my study. The precision in the position of the new part is also of great importance to have a good final result.
- During my literature study, I found some EU projects that are also related to this field, like RepAIR and FANTASIA. RepAIR is a project that aims at improving on-site maintenance and repair of aircraft components by using integrated direct digital manufacturing. The use of this technology increases the efficiency of the maintenance operations and results in more flexible availability. The project FANTASIA, focus at the development on additive manufacturing repair techniques but focus on two different technologies, Laser Metal Deposition (LMD) and Direct Laser Forming (DLF). Although these two projects are related to my field of study, not much information is available for research.
- The choice of material was made for Inconel 718. Inconel is nickel-chromium superalloy that has very good properties regarding strength, corrosion resistance and welding properties. Inconel is used for high end products that are submitted to very high temperatures, to which alluminum or steel would fail due to creep. SLM manufactured Inconel has been successfully tested and it has similar mechanical properties than the wrought material.
- Since there are many process parameters that may influence the SLM process and the interface quality, a specimen matrix, with 20 different specimen will be made, so that different parameters are analysed. Those specimen will have the geometry of a hollow cylinder (ADD CYLINDER FIGURE – DUPLICATE THE SLIDE - CHANGE PICTURE) and since our objective is to analyse the interface, they do not need to be large, and so they will have a small structure to avoid residual stress Those cylinders will be built on an Inconel surface plate. This plate has holes where the cylinders will be placed so that it fits exactly in their inner diameter, this way we can analyze the position accuracy of the process. The use of a machined surface plate represent the optimal conditions used for a preliminary study, but in actual repair situation some adaptions would have to be done. For example, a way of positioning the product accurately in the machine would have to be developed. Also, in a actual damaged product, there may be residual stresses that should be considered.
- Many processing parameters influence the SLM process but since the available time was short, some choices had to be made on which parameters should be varied and therefore studied and which should be kept fixed and follow the parameter optimization already carried out by NLR. Our choice was then based on the available time and in the influence the parameters have in the interface quality, that is our main study objective. Some parameters that are important for strength, like building direction, for example are not important for interface quality and therefore will be kept fixed in the simplest form or following what has been optimized for this kind of material.
- Finally, the parameters to be varied will be the laser power and scan speed, that together make the laser intensity. The laser intensity can affect the melting of the existing surface plate and the porosity and microstructure of the specimen. The initial conditions will also be varied between specimens, because they can have a big influence in the interface, that is our focus of study. Decisions had also to be made regarding the fixed parameters. It was decided, for example, not to do a preheating or heat treatment so we could have a more clear understanding of the mechanisms acting on the process. The powder layer thickness and laser focus were also kept fixed throughout the experiment so the number of parameters to be analysed was not too big.
- Keeping our objective of evaluating the interface quality we will do microstructural and porosity analysis in the interface. We will also do Vickers micro hardness tests to understand the hardness distribution around the interface. Mechanical tests could also be useful to understand the strength of the bond, but to do so, bigger and more complex geometries have to be built and since this is a short and preliminary study, this will not be done at this stage.
- During this week we have the building of the parts, and then the specimen will be cut and tested. When the analysis are done, the remaining objectives will be to evaluate the results, that is, the influence of the process parameters analysed in the final products. After is done, the point is try to describe a procedure on how to do the building on existing parts, analyse what factors can be improved and what may be useful and what is not. Then a report will can be written.
- This was a small presentation about my internship here at NLR and the objectives and procedure of my study on metal additive manufacturing on existing products.