Papers by Author: Marta Kianicová

Abstract: Authors of the paper present different types of tool wear after machining of weld overlay with AlTiN cutting insert. Welded layer was created on roller made from S355J0 steel by Open Arc (OA) method also referred as Metal One Gas (MOG). Various forms of tool wear were documented by optical microscope. Microchipping of cutting edge, built up edge (BUE) and flank wear were identified on examined round insert in rough turning of hard cladding.

Abstract: The microstructure and corrosion behaviour was studied for a diffusion β-NiAl and Si modified β-NiAl coatings formed on the superalloy MAR-M 247. First type, β-NiAl coating was applied with the help of method “out-of-pack”. Second type, Si modified β-NiAl coating was applied by method “pack-cementation”. Diffusion coatings created protective, heat-activated layer which separated superalloy from aggressive environment. Corrosive environment was created by tablets Na₂SO₄ at 900°C. Technique of scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDS) was used to characterize the corrosion products. Experiment confirmed the advantages relating to the application of diffusion coating in aggressive environment which imitated environmental condition during operation of turbine engine. This experiment was made in cooperation with company PBS Velká Bíteš a. s., Velká Bíteš, Czech Republic and The Silesian University of Technology, Faculty of Materials Science and Metallurgy, Katowice, Poland.

Abstract: Fracture surfaces of two sets of rotor blades failed after strong testing procedures of aircraft engines in the test-stand are investigated by means of SEM. While the process of fatigue fracture in the first set of blades did not reveal any defect features, both the initiation and propagation of fatigue cracks was strongly influenced by casting defects.

Abstract: Room temperature fatigue behaviour of two variants of diffusion aluminide coatings and conventional air plasma sprayed CoNiCrAlY + ZrO₂-Y₂O₃ thermal barrier system, which were deposited on a cast nickel-based supperalloy substrate, was studied under symmetrical bending loading regime. The study elucidates the differences in a fatigue crack initiation micromechanism with respect to applied stress level and its impact on the fatigue performance of studied coating systems.

Abstract: Nickel-based creep resisting alloys (strengthened by γ´) are the basic materials for high-temperature constructional parts in aircraft engines and energy units. These parts are exposed to combined effects of mechanical stresses, high temperature and dioxide-corrosion conditions. The microstructure changes of cast polycrystalline Ni-based superalloy IN713LC after creep exposure were studied. Three specimens with three different diameters were used for creep tests. The degradation stage (damage parameter π) was determined for all parts of specimens. Individual parts of specimens were metallographic observed and analyzed by image analysis after rupture. The results were compared with model of stress distribution in the specimen with potential damage in the centre of the specimen.

Abstract: Protective layers are used to improve high temperature performance of structural materials. However, the effect of coatings on mechanical and fatigue properties is not sufficiently known because it is a combination of many factors as high-temperature exposure time, thermal cycle and coating deposition technique. Interactions between the coating and the substrate under high-temperature conditions influence the life time of coated blades. This paper is focused on the study of microstructure and properties of aluminide protective layers deposited on cast polycrystalline nickel base superalloy Inconel713LC. The light microscopy with image analyses and scanning electron microscopy with energy dispersion spectroscopy were used. The surface treated specimens exposed at 800 °C in air and cylindrical specimens with protective layer cyclically loaded under strain control at 800 °C in air were studied. Experimental data on thickness, uniformity and chemical analysis of individual phases are obtained for as-coated specimens, for specimens exposed to 800 °C for 500 hours in air and for specimens fatigued to fracture at 800 °C in air.

Abstract: Diffusion Al-Si coatings are often used to protect rotor blades of aircraft engines against high-temperature corrosion in environments containing sulfur compounds. Besides other microstructural changes, the degradation of AlSi layers can be indicated by an increasing amount of surface oxide phases and changes in parameters of the layer geometry. In practice, the timetemperature area beyond a critical temperature of the outgoing gas is used as an empirical exploitation parameter D indicating a degradation level. The efficiency of such approach was investigated by analyzing degradation features in the surface layers of rotor blades after exploitations corresponding to different values of D. Determined simple relationships between the relative thickness of degraded layer and the parameter D verify the methodology and yield its clear geometrical interpretation. However, this method fails to provide reasonable information in case when the gas is burning outside the combustion chamber due to a sudden decrease of turbine revolutions.