Papers by Keyword: CMSX-4

Paper TitlePage

Authors: Włodzimierz Bogdanowicz, Robert Albrecht, Arkadiusz Onyszko, Jan Sieniawski
Abstract: Characterization of structure defects in turbine blades is the basis for determination of the overall crystalline perfections. This work presents the possibilities of identifying casting defects by combining different X-ray diffraction techniques. The investigation was conducted on samples prepared from as-cast turbine blades airfoil and tips. It was found that X-ray topograms revealed dendritic structure and macro strain areas. The defects areas which have appeared on topograms were also investigated by X-ray diffraction mapping technique by EFG diffractometer. Additionally, the X-ray investigation was complemented by macro SEM images obtained by stitching several images of microstructure. The X-ray maps of misorientation angle and X-ray topograms revealed deviation between the γ’ direction and the blade axis and rotation of the primary dendrite arm around this axis.
Authors: Włodzimierz Bogdanowicz, Robert Albrecht, Jan Sieniawski, Krzysztof Kubiak, Arkadiusz Onyszko
Abstract: In the work the single-crystalline alloy CMSX-4 was studied. The main aim of the study was an attempt to find correlations between images of X-Ray topography, X-ray diffraction maps of lattice parameter and misorientation angle and Scanning Electron Microscopy (SEM) images obtained by back-scattered electron (BSE) technique. Topography images were obtained by Auleytner method with wide beam. Diffractometer provided by EFG company was used for obtaining orientation and lattice parameter maps. Material for research was produced in Research and Development Laboratory for Aerospace Materials of Rzeszów University of Technology. Casts were obtained in ALD furnace by the Bridgman technique. It was found that X-ray topograms were correlated with SEM images of microstructures as well as with orientation and lattice parameter maps. X-Ray topograms showed high contrast bands which corresponded to dendrite arms. There was a correlation between low angle boundary and lattice parameter map.
Authors: Agnieszka Szczotok
Abstract: The heat-treatment processes for the precipitation-strengthened nickel-based superalloys are extremely complicated. The solution heat treatments are designed to dissolve the gamma-prime and the secondary carbide phases and allow the optimum re-precipitation of these phases upon cooling or after aging, for various precipitation-strengthened superalloys. The study was conducted to examine the effects of two solutionizing heat treatments on the microstructure of the CMSX4 superalloy. A comparison between the two obtained microstructures was performed.
Authors: Ludvík Kunz, Petr Lukáš, Rastilav Mintách
Abstract: The lifetime of superalloy single crystals CMSX-4 and CM186LC subjected to tensile mean stress with vibrations at high temperatures has been experimentally studied. Both beneficial and detrimental effect of cyclic stress component has been observed. An increase of lifetime due to superposition of cyclic component on the mean stress is explained by reduction of creep rate due to vibrations. The onset of decrease of lifetime with increasing stress amplitude is observed when the fatigue damage due to initiation and propagation of fatigue crack overbalances the beneficial influence of high frequency cycling.
Authors: Quan Wen, Qiang Feng, Guang Hua Cheng, Wei Zhao, Zu Qing Sun
Abstract: The femtosecond laser ablation has been investigated on second generation single crystal superalloy CMSX-4 using a commercial titanium:sapphire laser system (λ = 780nm, τ = 120 fs). The ablation thresholds of bulk alloy CMSX-4 have been determined as a function of the pulse number (1, 10, 100, 1000) in air, argon gas and vacuum. The results indicate that the multiple-pulse threshold of this material decreased with increasing the pulse number in all the cases. For the same pulse number, the threshold changed in the descending order: air, vacuum and argon gas. The incubation coefficient in air has been determined: ξ = 0.86 ± 0.03. The preliminary results showed the better quality of femtosecond laser machining of CMSX-4 in vacuum and argon gas than in air.
Authors: Ekaterina Rzyankina, Dariusz Szeliga, Nawaz Mahomed, Andrzej Nowotnik
Abstract: The occurrence of high temperatures in combustion chambers of jet engines and gas turbines has led to the demand for new technologies and new materials for the manufacture of one of the most critical elements of these systems - the turbine blades. These elements have to withstand extreme temperatures for extended periods without loss of mechanical strength, conditions under which many alloys fail. Such failure is ascribed to the combination of high temperatures and high centrifugal forces, resulting in creep. This is especially prevalent in multi-crystalline structures in which grain boundaries present weaknesses in the structure. High temperature resistant alloys formed as single crystal (SX) structures offer the necessary material properties for safe performance under such extreme conditions. Modelling and simulation techniques were first used to study the directional solidification (DS) of crystal structures during vacuum investment casting. These models allowed the study of the dendritic growth rate, the formation of new grains ahead of the solid/liquid interface and the morphology of the dendritic microstructure. These studies indicated the opportunity to optimise the velocity of the solidification front (solidification rate) for single crystal structures. The aim of this study was therefore to investigate the effect of the solidification rate on the quality of SX castings. The investigations were carried out for nickel-based superalloy CMSX-4 turbine blade casts and rods using the Bridgman process for vacuum investment casting.
Authors: Andrzej Nowotnik, Paweł Rokicki, Paweł Pędrak, Slawomir Kotowski, Jan Sieniawski, Grazyna Mrówka-Nowotnik
Abstract: Variations of a true stress vs. true strain illustrate behaviour of materials during plastic deformation. Stress-strain relationship is generally evaluated by a torsion, compression and tensile tests. Results of these tests provide crucial information pertaining to the stress values which are necessary to run deformation process at specified temperature and cooling rate. Uniaxial compression tests at temperatures below the γ solvus were conducted on nickel based superalloy CMSX-4, to study the effect of temperature and strain rate on its flow stress. On the basis of received flow stress values activation energy of a high-temperature deformation process was estimated. Mathematical dependences (σpl -T i σpl - ἐ) and compression data were used to determine material constants. These constants allow to derive a formula that describes the relationship between strain rate, deformation temperature and true stress.
Authors: Akio Hirose, Daisuke Nakamura, Hiroto Yanagawa, Kojiro F. Kobayashi
Authors: Edson Costa Santos, Katsuyuki Kida, Phil Carroll, Rui Vilar
Abstract: In this paper, results concerning the microstructure of Rene N4 alloy layers produced by laser cladding on oriented CMSX-4 single crystal substrates are presented. The microstructure of the deposits was analyzed in the solidification condition after different temperature/time ageing cycles in order to assess the possibility of improving high temperature strength of laser deposited superalloys. The present work demonstrates that single crystalline deposits of René N4 nickel superalloy can be obtained provided that the deposition direction and the processing parameters are properly selected. The clad layer is perfectly bonded to the substrate and presents no pores or cracks. The deposits grow epitaxially on the substrate, so they inherit its orientation. For laser beam powers and scanning speeds varying between 500 to 800 W and 4 to 12 mm/s, respectively and (001) substrates, the deposited material presents a columnar dendritic structure consisting of arrays of similarly oriented dendrites, separated by subgrain boundaries, forming a single crystal. Heat treatments effective for the dissolution of detrimental phases and for inducing the precipitation of cuboid ’-Ni3Al strengthening phase precipitates in the laser clads were established.
Showing 1 to 10 of 10 Paper Titles