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Item type:Publication, Access status: without files , Densification behavior, microstructure evolution, and wear property of TiC nanoparticle reinforced AlSi10Mg bulk-form nanocomposites prepared by selective laser melting(Laser Inst. of America, 2014-12-09); ; ; ; Selective laser melting (SLM), due to its unique additive manufacturing processing philosophy, demonstrates a high potential in producing bulk-form nanocomposites with novel nanostructures and enhanced properties. In this study, the nanoscale TiC particle reinforced AlSi10Mg nanocomposite parts were produced by SLM process. The influence of "laser energy per unit length" (LEPUL) on densification behavior, microstructural evolution, and wear property of SLM-processed nanocomposites was studied. It showed that using an insufficient LEPUL of 250-J/m lowered the SLM densification due to the balling effect and the formation of residual pores. The highest densification level (>98% theoretical density) was achieved for SLM-processed parts processed at the LEPUL of 700-J/m. The TiC reinforcement in SLM-processed parts experienced a structural change from the standard nanoscale particle morphology (the average size 75-92-nm) to the relatively coarsened submicron structure (the mean particle size 161-nm) as the applied LEPUL increased. The nanostructured TiC reinforcement was generally maintained within a wide range of LEPUL from 250 to 700-J/m and the dispersion state of nanoscale TiC reinforcement was homogenized with increasing LEPUL. The sufficiently high densification rate combined with the uniform distribution of nanoscale TiC reinforcement throughout the matrix led to the considerably low coefficient of friction of 0.38 and wear rate of 2.76-×-10-5 mm3 N-1 m-1 for SLM-processed nanocomposites at 700-J/m. Both the insufficient SLM densification response at a relatively low LEPUL of 250-J/m and the disappearance of nanoscale reinforcement at a high LEPUL of 1000-J/m lowered the wear performance of SLM-processed nanocomposite parts.Publicationtype: Journal Article27 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Correlations of melt pool geometry and process parameters during laser metal deposition by coaxial process monitoring(Elsevier, 2014-09-09); ; ; ; One major demand of today's laser metal deposition (LMD) processes is to achieve a fail-save build-up regarding changing conditions like heat accumulations. Especially for the repair of thin parts like turbine blades is the knowledge about the correlations between melt pool behavior and process parameters like laser power, feed rate and powder mass stream indispensable. The paper will show the process layout with the camera based coaxial monitoring system and the quantitative influence of the process parameters on the melt pool geometry. Therefore the diameter, length and area of the melt pool are measured by a video analytic system at various parameters and compared with the track wide in cross-sections and the laser spot diameter. The influence of changing process conditions on the melt pool is also investigated. On the base of these results an enhanced process of the build-up of a multilayer one track fillet geometry will be presented.Publicationtype: Conference PaperScopus© Citations 94 47 171 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , LMDCAM, computer aided manufacturing (CAM) solution for tool path generation for build-up of complex aerospace components by laser metal deposition (LMD)(Old City Publishing, 2014-01-01); ; ; ; The success of laser metal deposition (LMD) for repair or fabrication of near-net shaped metals components directly from computer aided design (CAD) solid models without use of time and cost-prohibitive conventional techniques, such as five-axis milling, linear friction welding and electro chemical machining depends on the availability of a close CAD/ computer aided manufacturing (CAM) chain. Distortion and defects of a worn part implies that the nominal CAD model from the design stage is no longer suitable for the representation of the part geometry. This means that first of all the actual and the target geometry have to be constructed from which the deficit volume is determined. Only with this volume being available the tool paths can be programmed. The original data format of laser scanned data is a polygonal modelling approach for surface representation. The further step of creating a non-uniform rational B-spline (NURBS) representation of the geometry requires a major commitment in time, both in instruction and in amount of work. For this reason the Fraunhofer Institute for Laser Technology (ILT) designed a process chain for the laser material deposition (LMD) whose CAM module termed LMDCAM, is based on a polygonal modelling approach for geometry representation. NURBS are only used for the reduction of data noise in the scanned data. The target geometry of worn parts is derived by a best fit with the CAD model from the design stage. LMDCAM supports the generation of all sorts of path pattern within a layer which for example may be derived from a distortion reduction analysis. The functionalities of LMDCAM are exemplified by a repair application and the near-net fabrication of a blade-integrated disk (BLISK) blade direct from the CAD model.Publicationtype: Journal Article30 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Digital photonic production: High power ultrashort lasers, laser additive manufacturing and laser micro/ nano fabrication(Optical Society of America (OSA), 2012-11); ; ; ; The high power optical technologies enter a new era: The age of DIGITAL PHOTONIC PRODUCTION. Very recently new lasers in new time- and wavelength domains with high average powers have been developed for new processes like Laser Additive Manufacturing, Laser Ablation by ultrafast lasers or Laser Polishing.Publicationtype: Conference Paper17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Modeling of coaxial single and overlap-pass cladding with laser radiation(Springer, 2012-07); ; ; ; The repair with laser cladding of single crystalline Nibase superalloy gas turbine blades requires specific solidification conditions in order to realize an epitaxic dendritic growth front. For each superalloy there exists a process window concerning solidification conditions within the formation of new grains ahead of the epitaxic dendritic growth front can be prevented. In order to determine this process window a three-dimensional finite element model for laser cladding has been developed. This model emphasizes on a precise calculation of free surface shape of melt pool because the microstructure as processed depends essentially on the solidification conditions around the solidus/liquidus temperature. So due to the small distance between the melt pool surface and the growth front all errors concerning the approximation of melt pool surface and the implementation of boundary conditions will be mapped directly onto the solidification conditions. This model does not use any geometrical approximation of the melt pool surface but determines the melt pool surface shape by the balance equation for capillary forces.Publicationtype: Conference Paper29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , LACAM3D, CAM solution for tool path generation for build up of complex aerospace components by laser powder deposition(Springer, 2012-07); ; ; ; This The success of Laser Metal Deposition (LMD) for repair or fabrication of near-net shaped metals components directly from CAD solid models without use of time and cost-prohibitive conventional techniques, such as five-axis milling, linear friction welding and electro chemical machining depends on the availability of a close CAD/CAM chain. Distortion and defects of a worn part implies that the nominal CAD model from the design stage is no longer suitable for the representation of the part geometry. This means that first of all the actual and the target geometry have to be constructed from which the deficit volume is determined. Only with this volume being available the tool path programmed. The original data format of laser scanned data is a polygonal modeling approach for surface representation. The further step of creating a NURBS representation of the geometry requires a major commitment in time, both in instruction and in amount of work. For this reason the ILT designed a process chain for the LMD whose CAM module, LACAM3D, is based on a polygonal modeling approach for geometry representation. NURBS are only used for the reduction of data noise in the scanned data. The target geometry of worn parts is derived by a best fit with the CAD model from the design stage. LACAM3D supports the generation of all sorts of path pattern within a layer which for example may be derived from a distortion reduction analysis. The functionalities of LACAM are exemplified by a repair application and the near-net fabrication of a BLISK (Blade-Integrated diSK) blade direct from the CAD model.Publicationtype: Conference Paper27 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Reconditioning of Nickel base HPT blades and vanes used in aero engines and power plant gas turbines by combination of direct laser forming, laser metal deposition and laser drilling(LIA, 2006-04); ; ; ; Parts like HPT (High Pressure Turbine) blades and vanes with integrated complex shaped cooling channels cannot be repaired. The parts are replaced by new ones. The aim is to develop and implement a reconditioning chain to avoid scrapping of the part. The reconditioning chain covers the three different Laser Applications 1. Direct Laser Forming (DLF), 2. Laser Metal Deposition (LMD) and 3. Laser Drilling (LD) which are arranged in subsequent Processing Steps. The damaged volume of the blade or vane is replaced by a fitting patch with integrated cooling channels which is generatively manufactured by DLF based on CAD data acquired by digitizing and reverse engineering in a first step. The generated patch is joined into the remaining part of the blade or vane by LMD. The non open cooling channels are opened and in case of necessity reshaped by LD in the third step. Also the cooling channels damaged or destroyed in the joint zone patch-substrate by the LMD joining process within step 2 are reworked or inserted by LD in the third step. First results achieved within basic R & D of DLF, LMD and LD of relevant Nickel Base Alloys are presented.Publicationtype: Conference Paper17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Laser metal deposition of tial alloysLaser Metal Deposition (LMD) is a validated process for repairing aero engine parts and complete components. An increase of specific efficiency of aero engines is achieved by replacement of heavy parts out of Nickel Base Alloys in the HPC (High Pressure Compressor) and LPT (Low Pressure Turbine) sectors by lightweight parts out of TiAl Alloys in operating temperature ranges from 450 up to 700 °C. Due to the use of these upcoming new materials and non available repair techniques the market requires adequate R & D and repair development for specific parts and components. First results achieved within basic R & D of LMD of TiAl Alloys are presented. The determined suitable process parameter windows including suitable preheating temperature ranges to achieve defect free (crack free, pore free and bonding defect free) Laser Metal Deposits are shown. The influences of the process parameters on the results achieved by LMD are discussed.Publicationtype: Conference Paper47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Laser cladding as a repair technique for blisks out of titanium and nickel base alloys used in aero enginesThe most commonly used materials in aero engines are Nickel and Titanium base alloys. Exemplary for these types of alloys the macro and micro structure and the static and dynamic mechanical properties of the laser cladded Nickel base Superalloy Inconel 718 and the laser cladded Titanium base alloys Ti-17, Ti-6A1-4V and Ti-6246 are described and discussed in a first step. Based on the results achieved within step 1 the process layout is transferred and adapted onto real components in a second step. Tip and leading edgerepairs of real components are demonstrated.Publicationtype: Conference Paper21