MTU Maintenance Hanover GmbH

Langenhagen, Germany

MTU Maintenance Hanover GmbH

Langenhagen, Germany
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Kaierle S.,Laser Zentrum Hannover e.V. | Overmeyer L.,Laser Zentrum Hannover e.V. | Overmeyer L.,Leibniz University of Hanover | Alfred I.,Laser Zentrum Hannover e.V. | And 4 more authors.
CIRP Journal of Manufacturing Science and Technology | Year: 2017

High pressure single-crystal turbine blades made from nickel-based superalloys can withstand temperatures of up to 1100. °C due to their superior creep and fatigue properties compared to polycrystalline material. However, these parts undergo erosion and cracking due to the extreme conditions they are subject to in the engines of commercial airplanes. Since there is no effective method of repairing these expensive parts, while maintaining the necessary microstructure, the need to develop and establish a reproducible process is of high importance. The process of Laser Material Deposition (LMD) has shown promising results in the building-up of single-crystal or directionally solidified structures, while laser remelting has been shown to extend this monocrystalline height. By combining the two processes, this study aimed to deposit and remelt single-crystal structures on substrates of the nickel-based superalloys CMSX-4 and turbine blade tips of PWA 1426. Experiments were carried out to establish laser parameters that resulted in a monocrystalline microstructure. This study showed that the combination of cladding and remelting can be used to deposit single-crystal structures and was able to establish a reproducible laser process to this effect. The results obtained indicate that the process is a promising candidate for the repair of turbine blade tips and warrants further research into the microstructure and thermomechanical properties of the repaired areas. © 2017 CIRP.

Naraparaju R.,German Aerospace Center | Schulz U.,German Aerospace Center | Mechnich P.,German Aerospace Center | Dobber P.,MTU Maintenance Hanover GmbH | Seidel F.,MTU Maintenance Hanover GmbH
Surface and Coatings Technology | Year: 2014

A damage assessment of TBC (thermal barrier coatings) coated combustion chamber parts of aero-engines after service in CaO-MgO-Al2O3-SiO2 (CMAS) loaded areas was performed in this study. Parts from different aero-engines were investigated by scanning electron microscopy (SEM) and the extent of damage of the 7wt.% yttria stabilised zirconia (7YSZ) plasma-sprayed TBC due to CMAS deposition and infiltration was estimated. With the help of SEM and energy-dispersive spectroscopy (EDS), CMAS chemical composition was analysed and two different typical chemical compositions of CMAS were derived. These model CMAS compositions were synthesised in laboratory and their melting behaviour was determined by means of differential scanning calorimetry (DSC). Both CMAS variants were subsequently deposited on air plasma sprayed yttria stabilised zirconia (APS-7YSZ) TBC specimens. Samples were subjected to isothermal heat treatments in air at temperatures ranging from 1200°C to 1250°C for times between 10h and 100h. The phase formations and microstructural changes were examined by SEM and X-ray diffractometry (XRD). Results from the CMAS/TBC interaction experiments could duplicate with the damage patterns on the real combustion chamber parts. Furnace cycle tests (FCT) were conducted at 1135°C on TBC coated buttons with and without CMAS. The extent of TBC damage strongly correlates to the CMAS composition. The presence of Ca-sulphate (CaSO4, anhydrite) in the CMAS plays a large role in damaging the 7YSZ and infiltration depth of CMAS. With raising temperature, the depth of infiltration increases rapidly and the CMAS has penetrated completely throughout the TBC thickness at 1250°C. In addition, the time to failure of the TBCs strongly depended on the type of CMAS deposited. The life time of the samples with CaSO4 containing CMAS was found to be the lowest compared to the samples without CMAS and with the CaSO4 free CMAS variant. © 2014 Elsevier B.V.

Grueninger A.,Laser Zentrum Hannover e.V. | Weidlich N.,MTU Maintenance Hanover GmbH | Meier O.,LASER on Demand GmbH | Deutschmann M.,MTU Maintenance Berlin Brandenburg GmbH
International Journal of Microstructure and Materials Properties | Year: 2010

Increased passenger safety and the reduction of the fuel consumption of vehicles are conflicting targets. However, the combination of lightweight construction with high strength steels or aluminium sheets is a promising approach to reach this goal. Very hard forming die surfaces are necessary for forming high strength steels. A new technology for generating very hard surfaces with high abrasion resistance is laser particle injection, also known as laser dispersing. During laser particle injection, ceramic particles are brought into the forming die surface. Laser particle injected layers are highly resistant against abrasive and adhesive wear. If damage should occur, the hard particles move with the ductile matrix but do not separate from it. At the Laser Zentrum Hannover e.V. (LZH), zirconium dioxide (ZrO2) is currently under close investigation. ZrO2 has the great advantage that the coefficient of thermal expansion is similar to steel. The paper presents an overview about possibilities and limits of laser particle injection for wear resistance, using ZrO2. Copyright © 2010 Inderscience Enterprises Ltd.

Marx J.,MTU Maintenance Hanover GmbH | Stading J.,MTU Maintenance Hanover GmbH | Reitz G.,TU Braunschweig | Friedrichs J.,TU Braunschweig
CEAS Aeronautical Journal | Year: 2014

Due to environmental and operational effects, the deterioration of all gas path-related jet engine components is a highly influencing parameter leading to an increase in exhaust gas temperature and specific fuel consumption over time. As a particularly strained engine module, the high-pressure compressor (HPC) is prone to a variety of abrasive and deforming effects that are responsible for a considerable part of overall engine performance losses. During HPC overhaul, new airfoils are typically mixed with reused parts whose refurbishment workscopes typically range from “passed inspection” up to “full leading and/or trailing edge restoration” as well as “tip weld repair”. Hence, a wide spread of airfoil geometries with a distinct statistical distribution can be found within an engine after operation. To allow a statistical analysis, a geometric survey on two full ex-service HPC blade sets and an assortment of equivalent new production parts was conducted. The blades were digitalized by a structured-light 3D scanner in conjunction with a photogrammetry system. Based on the measured three-dimensional data, a CAD model was generated for each blade. Afterwards, airfoil sections on different blade heights were analyzed to generate aerodynamic design parameters such as leading and trailing edge geometries (radius and thickness), their maximum profile thickness, their chord length and their stagger angle. By assessing the statistical results of both used and new parts, the effects of manufacture variations and in-service wear on HPC blade geometry can be compared in detail. © The Author(s) 2014. This article is published with open access at

Ebmeyer C.,Hamburg University of Applied Sciences | Friedrichs J.,TU Braunschweig | Wensky T.,MTU Maintenance Hanover GmbH | Zachau U.,MTU Maintenance Hanover GmbH
Proceedings of the ASME Turbo Expo | Year: 2011

The current maintenance and overhaul of large civil jet engines is completely based on-condition and is widely customized to the individual requirements of the operation. Therefore, a very important factor for an effective and economic engine maintenance program is the investigation and appreciation of the current engine condition, as well as its individual deterioration mechanism. This paper is introducing a method to analyze the engine performance deterioration between two typical off-wing maintenance events (shop visits) so as to draw conclusions for maintenance planning and operation. In order to perform a precise evaluation the performance analysis is conducted on a modular level. Therefore the engine is divided into the following major modules: FAN, LPC, HPC, combustor, HPT, LPT and exhaust nozzle. The basis for the evaluation is the overhauled engine condition after a shop visit (pass-off test run) and the deteriorated engine condition after operation (incoming test run). These two points in the engine life cycle provide specific engine conditions that are to be analyzed by scientific and commercial software, and combined with a self-developed engine performance model in order to obtain the desired results: The individual engine deterioration during operation demonstrated by the differences of the modular performance between incoming test run and the last pass-off test run. In addition, to ensure the continuous monitoring of the performance status between the two test runs, it is important to analyze the "on-wing operation". This is done using MTU's Engine Trend Monitoring (ETM) system, which generates performance data based on the available in-flight data. In this paper an analysis example is used to present the analytic method and the obtained results. Reasons of deterioration are evaluated separately in reference to different environmental influences from specific geographical regions. In summary this paper introduces a solution to track the total engine performance based on modular evaluation values, starting at improvements for pass-off and incoming test runs as well as performance degradation during the on-wing time. Copyright © 2011 by ASME.

Eickemeyer S.C.,Leibniz University of Hanover | Borcherding T.,Leibniz University of Hanover | Schafer S.,MTU Maintenance Hanover GmbH | Nyhuis P.,Leibniz University of Hanover
Production Engineering | Year: 2013

The regeneration of complex capital goods is afflicted with a high degree of uncertainty. Neither the extent of the damage to the goods nor the resulting maintenance workload is known in advance, and that poses challenges for capacity planning. Data fusion in the form of Bayesian networks is used to prepare forecasts in order to estimate the workload in maintenance processes. The objective is to optimize the planability of the capacities required. © 2013 German Academic Society for Production Engineering (WGP).

Munkelt C.,Fraunhofer Institute for Applied Optics and Precision Engineering | Kuhmstedt P.,Fraunhofer Institute for Applied Optics and Precision Engineering | Aschermann L.,MTU Maintenance Hanover GmbH | Seidel F.,MTU Maintenance Hanover GmbH
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

High-resolution contactless optical 3D measurements are well suited for determination of state and position of gas turbine vane cooling-holes during maintenance rework. The air flow through the cooling-holes protects the turbine vanes from the high temperatures. However, the coating needs to be renewed during repair of the vanes. The renewal process can lead to partially or completely filled cooling-holes. This paper describes a newly developed procedure to automatically detect and reopen such holes by laser-drilling for an effective new repair process. The turbine vane is scanned by a fringe projection based optical 3D scanner. The resulting 3D pointcloud delivers plenty of detail to automatically detect the cooling-holes. Poorly detected or undetected cooling-holes are interpolated from properly detected neighboring cooling-holes and reference default cooling-holes. For the resulting laser-drilling process the precise orientation in the vane mount must be known. To this end, position and orientation of the scanned vane in relation to the reference vane is determined. To validate the approach, numerous experiments regarding the cooling-hole extraction-performance were satisfactorily conducted. Real drilling experiments confirmed those findings and were used to validate the entire process. © 2015 SPIE.

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