Institute of Fundamental Technological Research
Polish Academy of Sciences


Stefania Woźniacka

Department of Mechanics of Materials (ZMM)
Division of Surface Layers (PWW)
position: senior technician
telephone: (+48) 22 826 12 81 ext.: 141
room: 231

Recent publications
1.  Kucharski S., Woźniacka S., Size effect in single crystal copper examined with spherical indenters, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-019-05160-w, Vol.50A, pp.2139-2154, 2019

The increasing hardness with decreasing penetration depth, referred to as indentation size effect (ISE) was previously investigated experimentally and theoretically by many researchers, however the mechanisms responsible for ISE are still being discussed. Generally, ISE is related to the density of geometrically necessary dislocation stored within a small volume beneath the indenter tip. In this study ISE is investigated experimentally in a single crystal copper using spherical indenter tips of different radii. Some new aspects of ISE are shown: a qualitative change of shape of residual impression (pile-up/sink-in pattern) when tip radius or load is modified, an increase of maximum pop-in load with decrease of tip radius as well as the well-known increase of hardness when tip radius decreases are analyzed. As we observe a difference of the residual imprint morphology which depends on tip radius and load, we apply two methods of hardness estimation: true hardness and nominal hardness. The former is determined on the basis of direct measurement of the contact area while accounting for a specific pile-up pattern, while the latter is determined by measuring the contact area using residual penetration depth. We show that hardness–tip radius relationship has a linear form for the nominal hardness and bilinear form for the true hardness.

Kucharski S. - IPPT PAN
Woźniacka S. - IPPT PAN
2.  Chrzanowska-Giżyńska J., Denis P., Woźniacka S., Kurpaska Ł., Mechanical properties and thermal stability of tungsten boride films deposited by radio frequency magnetron sputtering, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2018.07.208, Vol.44, No.16, pp.19603-19611, 2018

Tungsten and boron compounds belong to the group of superhard materials since their hardness could exceed 40 GPa. In this study, the properties of the tungsten boride WBx coatings deposited by radio frequency magnetron sputtering were investigated. The sputtering was performed from specially prepared targets that were composed of boron and tungsten mixed in a molar ratio of 2.5 and sintered in Spark Plasma Sintering (SPS) process. WB films were deposited on silicon (100) and stainless steel 304 substrates at temperatures of 23 ÷ 770 °C. Microstructure, chemical and phase composition were investigated by using Scanning Electron Microscope (SEM), X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Diffraction (XRD), respectively. The mechanical properties like Vickers hardness and Young's modulus were obtained by using nanoindentation test at a load of 5 ÷ 100 mN. The friction coefficient and wear resistance of αWB coatings were investigated in scratch test and reciprocal sliding wear instrumentation. Moreover, in order to investigate thermal properties, the αWB films were annealed at 1000 °C in argon/air for 1 h and at 250 °C for 2 h in air atmosphere. Results of our research confirm that αWB coatings can be considered as an alternative to superhard materials in the production of wear resistant, long-lasting tools.

Hard coatings, Hard materials, Magnetron sputtering, Mechanical properties, Thermal properties, Tungsten boride

Chrzanowska-Giżyńska J. - IPPT PAN
Denis P. - IPPT PAN
Woźniacka S. - IPPT PAN
Kurpaska Ł. - National Centre for Nuclear Research (PL)
3.  Kucharski S., Jarząbek D.M., Piątkowska A., Woźniacka S., Decrease of Nano-hardness at Ultra-low Indentation Depths in Copper Single Crystal, EXPERIMENTAL MECHANICS, ISSN: 0014-4851, DOI: 10.1007/s11340-015-0105-2, Vol.56, No.3, pp.381-393, 2016

In the present study, we report a detailed investigation of the unusual size effect in single crystals. For the experiments we specified the hardness in single crystalline copper specimens with different orientations ((001), (011) and (111)) using Oliver-Pharr method. Our results indicates that with decreasing load, after the value of the hardness reached its maximum, it starts to decrease for very small indentation depths (<150 nm). For the sake of accuracy of hardness determination we have developed two AFM-based methods to evaluate contact area between tip and indented material. The proposed exact measurement of the contact area, which includes the effect of pile-up and sink-in patterns, can partially explain the strange behaviour, however, the decrease of hardness at low loads is still observed. At higher loads range the specified hardness is practically constant.

Copper, Single crystal, Nanoindentation, AFM, Size effect

Kucharski S. - IPPT PAN
Jarząbek D.M. - IPPT PAN
Piątkowska A. - Institute of Electronic Materials Technology (PL)
Woźniacka S. - IPPT PAN

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