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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 , Deposition welding of hot forging dies using nanoparticle reinforced weld metal(Springer, 2014-06-26); ; ; ; In the application field of forging, the form-giving tool components are subject to process-related severe environmental conditions, such as high mechanical loads acting simultaneously with high tribological and thermal charges. Due to high machine hour rates as well as increasing environmental requirements in terms of energy consumption, wear protection methods and suitable repair measures for forging tools become more and more important. Laser deposition welding represents an established process for the repair of complex shaped surfaces. A new approach is the addition of nano-sized ceramic particles to improve the mechanical properties. The main idea is to reduce the grain size of the cladded layers by adding nano-sized nuclei. A fine grained microstructure will improve strength as well as ductility and fatigue resistance. Furthermore small hard particles can improve the wear resistance without affecting the friction of the surface. After the cladding process the surface has to be finished usually by turning, milling and grinding operations. Within the presented paper the potential of nanoparticle-reinforced deposition welding with regard to increasing the wear resistance of forging dies will be examined. First, the process of nanoparticle-reinforced deposition welding will be presented. Afterwards it will be shown that yttrium oxide, titanium carbide and tungsten carbide nanoparticles in an AISI H10 matrix material will influence the friction coefficient between forging tool and material as well as the wear properties.Publicationtype: Journal Article28 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Study on cracks in laser direct-cladded titanium layer on low carbon steelBy adjusting laser power and nozzle speed in laser cladding technology, crack-free titanium layer with even thickness and titanium mass percentage over 99%, was obtained on the substrate of low carbon steel without any intermediate layer when heat input was between 12-20 J/mm. The temperature field and the mechanical strain were simulated. Together with phase diagram and EDS, it was found that an interface zone, consisted of TiFe, (TiFe+β-Ti) eutectic compound and α-Ti, was formed between the titanium layer and the substrate. The interface zone is brittle and cracks occur in it. In titanium layer crack also occur if the mechanical strain exceeds the critical plasticity of metal. By reducing heat input, the mechanical strain decreases, thus a crack-free titanium layer with even thickness can be obtained.Publicationtype: Journal Article17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Increased wear and oxidation resistance of titanium aluminide alloys by laser claddingA process layout for laser cladding of layers on substrates of titanium aluminides using state-of-theart and modified (additions of Si and TiB2) TiAl alloys is presented. The process involves a preheating of the samples to reduce thermal stresses and cladding in an inert gas atmosphere with an oxygen content lower than 30 ppm. These conditions lead to crack free layers and low surface oxidation. Microstructure and hardness of the layers are investigated. The abrasive wear resistance of the cladded layers in comparison to the base material is tested with promising results. Finally results of the oxidation behavior are shown and prove the increased performance of modified TiAl layers in comparison to the base material.Publicationtype: Journal Article16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Applying functionally graded materials by laser cladding: a cost-effective way to improve the lifetime of die-casting diesThe lifetime and economic methods of improving the lifetime of a die-casting die are key factors for the die-casting industry since the global competition and the competition with other production techniques have increased significantly. The article depicts the approach, technical realization, latest results and process limitations of the INNOGRAD research project. Here, powder-based laser-cladding is applied to combine two materials as a functionally graded material. By applying gradient structures it is possible to fit the material to the predominant type of exposure, resulting in an increase in the lifetime of die-casting dies.Publicationtype: Conference Paper26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Functionally graded multi-layers by laser cladding for increased wear and corrosion protectionThe growing competition in the die casting industry requires extension of the lifetime of the moulds. This major demand can be fulfilled by increasing the wear resistance of the mould with hard surface layers to reduce erosion. Combining this feature with high tensile strength and high ductility, thermal or stress induced cracking during the casting process with its cyclic thermal and mechanical stresses can also be minimised or inhibited. However, commonly used hot working tool steels are limited regarding the required properties. Laser cladding is an established technique to increase wear and corrosion protection locally and it offers the possibility to combine properties by multi-graded layers.Publicationtype: Conference Paper17