Solid State Phenomena Vol. 186

Abstract: LaNi5 nano-powders with additions of Ce, Mn, Co (high and low content of cobalt) and Al were obtained by means of MBN technology, based on the high energy ball milling with different energy and protective atmosphere (Ar or H2). The microstructure and composition of all prepared nano-powders were investigated using the TEM/HRTEM, SEM/EDS, XRD and XPS techniques. Research showed that used technology allowed to produce materials distinguished by a fine and homogeneous chemical distribution of elements and an "ultrafine" (the nanometric size) crystalline structure. The results were then related to the preparation conditions.

Abstract: Powder metallurgy is widely used to the production of AgNi and AgSnBi powders employed for electrical contacts. In the work AgNi and AgSnBi powders were consolidated by the cyclic extrusion compression (CEC) method enabling cyclic unlimited deformation. In the initial stage the AgNi powder contained the two phases Ag and Ni, recognized by the EDX technique using scanning electron microscopy (SEM). The investigations shown that the Ni phase is distributed in the form of small granules around larger Ag granules. In the AgSnBi powder phases Ag + Bi + Ag3Sn (ξ) were distributed uniformly. It was found that after the CEC consolidation phases were excellently joined without cavities and cracks. Detailed observations of microstructure have been performed by the transmission electron microscopy (TEM) and revealed inside the consolidated granules nanometric grains with the nanometric twins inside.

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.

Abstract: TEM studies of the ex-service single crystal blade were performed to analyse the microstructural changes which control the degradation of the CMSX-4 superalloy during its exposure in a gas turbine. Microstructural analyses were focused mainly on evolution of the γ-γ’ morphology and examination of dislocation configurations in particular parts of the blade. Between the bottom and tip locations of the blade a pronounced differences in γ-γ’ morphology were observed. TEM analysis of the dislocation substructure showed that at the bottom of the blade the dislocation slip is mainly confined to the horizontal γ channels. Increasing of the temperature and decreasing of stress along the blade height resulted in the γ-γ’ rafting, formation of dislocation networks and intensification of the dislocation climb in vertical γ channels.

Abstract: This paper presents the degradation of hollow turbine blades made of ZhS6K nickel-based superalloy after service in DV2 aero engines. The blades were coated with a diffusive aluminide coating (Al-Si) to improve the oxidation and hot corrosion resistance. Turbine blades work under extreme conditions and a complex state of stress. During service, creep and fatigue of various natures take place. The interaction among hot combustion gases causes oxidation of the surface layer and hot corrosion and micro cracking of the coating. Moreover, changes in morphology of the γ’ phase just under the coating and transformations of the primary carbides take place. The factors limiting the lifetime of turbine blades are the quality of the aluminide coating andmicrostructure of the superalloy, depending on the service parameters—the temperature and the duration of service. It was found that exposure to high temperatures above the critical value for several seconds substantially decreased the engine power and its durability. In this paper, analysis of the microstructure, chemical composition and phase composition of the turbine blades after service were carried out. Evaluation of the extent of degradation was performed using the scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDS) and electron backscatter diffraction (EBSD) techniques. The EBSD technique was used to analyse the phase composition in micro areas, especially to identify carbides before and after transformations.

Abstract: Experimental results on hot deformation and dynamic structural processes of nickel based alloy Inconel 718 are reviewed. The focus is the analysis of dynamic precipitation processes which operate during hot deformation of these materials at elevated temperatures. Hot compression tests were performed on the solution treated precipitation hardenable nickel based superalloy Inconel 718 at 720-1150°C with a constant true strain rates of 10-4 and 4x10-4s-1. True stress - true strain curves and microstructure analysis of the deformed nickel based superalloy is presented. The properties and dynamic behaviour are explained through observation of the microstructure using standard optical, scanning and transmission electron microscopy. Structural observations of solution treated Inconel 718 deformed at high temperatures, reveal non uniform deformation effects. The distribution of niobium-rich carbides were affected by localized flow within the strain range investigated at relatively low deformation temperatures 720 - 850°C.

Abstract: The aircraft engines turbine blades are manufactured from nickel-base superalloys and they are often in a single crystal form. This ensures the best high-temperature creep resistance as compared with blades of equiaxial grains microstructure and of columnar grains microstructure. Turbine blades were manufactured in an ALD Vacuum Technologies furnace. The study has examined structural perfection of single crystal blades obtained by Bridgeman method from CMSX-4 nickel superalloy at various withdrawal rates: 1, 2, 3, 4 and 5mm/min.

Abstract: This paper characterizes the microstructure and mechanical properties of the nickel-based superalloy with the nominal composition Ni–25Mo–8Cr (wt.%) after long-term annealing (4000, 6000 and 8000 h) at 650°C. The microstructure was characterized by TEM and SEM. Mechanical properties were measured trough tensile testing. The microstructure, composed initially of a dispersive Ni2(Mo,Cr) strengthening phase in a Ni-based solid solution, decomposed during annealing into a mixture of intermetallic (Ni3Mo- and Ni4Mo-type) phases and recrystallized Mo-lean Ni-based solid solution. The dominant new phase was a plate-shaped Ni3Mo-type phase. Regions adjacent to the plates of the Ni3Mo phase are recrystallized and free from the Ni2(Mo,Cr) strengthening phase.

Abstract: The paper presented the structure (TEM), morphology and chemical composition (EDS) of the -Al-Mg thin films and Al-Mg-Ni multilayer obtained by pulsed laser deposition (PLD). This films were deposited using Nd:YAG laser. The different process parameters were applied. The Al-Mg film was obtained by application of the laser wavelength (=355 nm) and substrate temperature (Ts) 200 oC. Whereas the Al-Mg-Ni multilayer was produced at lower laser wavelength (=266 nm) and at room temperature of the substrate. For preparation of both films the same laser fluence (q=4.7 J/cm2) was used. The Al-Mg possessed nanocrystalline structure with the areas where only columnar Al crystals occurred. EDS of this thin film exhibited that in the nanocrystalline areas the chemical composition corresponded to the target content of Al and Mg. While Al-Mg-Ni multilayer composed of six layers. In this case Al-Mg layers were thinner then Ni layers. In the multilayer structure the fcc Al0.65Mg0.35 and fcc Ni phases was revealed.

Abstract: The WO3 films were grown by pulsed laser deposition on Si [100] substrate, using an Nd-YAG laser (=355 mm, LOTIS TII). The substrate was heated from 25°C up to 650°C and the films were deposited in oxygen pressures 5 Pa. To characterize the structure and morphology of the surface we used the XPS, Transmission and High Resolution Electron Microscopy (TEM, HREM). From XPS analyses, it was clearly established, that even though in PLD process was used oxygen atmosphere in thin films we observed two phases WO3 and small amount WO2. The amorphous structure with small crystalline we observed in thin films obtained at ambiance temperature. At temperature T = 650 °C TEM analysis show crystalline structure with crystalline about 5 ÷ 10 nm.