Solid State Phenomena Vol. 197

Abstract: In the paper first results of TBCs deposition by LPPS-Thin Film method were presented. The LPPS-Thin Film is a new type of processes for deposition of thermal barrier coatings. In this method deposition of thin ceramic layer in very low pressure is possible as well as coatings with columnar structure (in plasma spraying-physical vapour deposition process). The MeCrAlY bond coats were deposited by APS method. The overaluminising by CVD method of conventional MeCrAlY was also conducted. The analysis of microstructure of both type bond coats as well as outer ceramic layer were presented using light and scanning electron microscopy methods. Results of EDS microanalysis showed the increasing of aluminum content in outer zone of overaluminized MeCrAlY coating. In ceramic layer the columnar structure were observed which was connected with powder evaporation during plasma spraying. The new type of MeCrAlY-NiAl bondcoat could increase the oxidation of TBCs deposited by LPPS Thin Film method.

Abstract: The paper presents an analysis of the effectiveness of radiation modification of GUR 1050 and GUR 1020 polymers intended for endoprosthesis bearing components. It has been demonstrated through extraction and expansion that the crosslinking density increases as the applied dose of electron irradiation and the molecular weight of polyethylene grow. The recorded changes were accompanied by an increase in the degree of crystallinity, which was more significant in the case of the more heavy GUR 1050 (compared to GUR 1020). The morphological changes are supported by the results of micromechanical, sclerometric and tribological examinations. Tribological examinations were documented with SEM images of the surface of specimens subjected to oscillatory friction (roll-block tester). Series of crosswise valleys and projections, arranged along the friction direction, were found on the friction surface. The smoothening of the surface and a lack of lamella fragments on the base specimens which were not subjected to e-beam irradiation are observed along with a reduction of wear due to the increasing dose of irradiation.

Abstract: In this paper, an attempt has been made to determine the changes in the structure of UHMWPE under the influence of deformation, which can be the cause of the decrease of functional properties. It has been found that the degree of cross-linking slightly changes due to operational loads (deformation ef=0.15-0.6). The deformation leads, however, to the systematic lowering of the degree of crystallinity and an insignificant decrease of lamella width. Tests of wide- and small-angle X-ray scattering (WAXS, SAXS) prove that this is the result of operational deformation causing a rather weak texture of crystals and the fragmentation of some lamellae. Anisotropy of the lamellar structure also takes place, which changes 2D SAXS images into ellipses with a rapidly growing axial ratio with ef value.

Abstract: The paper presents the results of an examination of UHMW polyethylene type GUR1050 using the EPR, FTIR and SEM methods. The relationship between the number of radicals in the polymer and the absorbed dose of ionizing radiation has been shown. The radicals, being highly active macroparticles, disappear in time, so that after about a year their amount is reduced by approximately one order of magnitude. The disappearance of the radicals over time results in a change in EPR spectra, an increase in the degree of oxidation, and cross-linking. The most probable mechanisms are the formation of alkyl and allyl radicals and their gradual transitions, which lead to the absorption of atmospheric oxygen, and the recombination of radicals, which leads to the formation of cross linkages. Thermal treatment of the samples is an effective method of eliminating the radicals. Tribological tests and their analysis by means of SEM observation showed that the irradiated samples proved to have higher resistance to abrasion than the material that was not exposed to radiation.

Abstract: The effect of B and microalloying additions of V, V+Ti, V+Nb on austenite grain growth of low alloy steel containing 0.3% C, 1 % Cr and 0.2 % Mo was investigated. As a measure of austenite grain size the mean chord length of austenite grains was assumed. The boron content in investigated steel was in the range of 0 to 0.008 %. The investigations were carried out in austenitising temperature range of 850 to 1100oC. Using the thermodynamic model the contents of undissolved compounds of carbonitride V(C,N) and boron nitride BN were calculated and the effect of undissolved compounds content on austenite grain size was investigated. Obtained results showed, that vanadium content below 0.1 % was ineffective as austenite grain growth inhibitor of boron containing steel and austenite grain size of steel was higher compare to non-alloyed steel. The most effective for decreasing of austenite grains size of boron containing steel was addition of 0.18 % V + 0.03 % Nb

Abstract: The present work discussed the development of statistical analysis as a reproducibility assistance method for evaluation of advanced Fe-3%Mn-(Cr)-(Mo)-C sintered steel for high performance structural parts. Factors contributing to the reliability and reproducibility of these structural steels include advanced metal matrix with consistent purity and concentration of chemical constituents, as well as mix homogeneity and processing uniformity. Matrix inhomogeneity was found to play an important role in these materials. In this paper the statistical dependence between properties and processing variables of PM Mn-Cr-Mo steels is presented. The investigations of sintered steels were based on commercial powders: pre-alloyed Höganäs iron powders Astaloy CrM and Astaloy CrL and graphite C-UF. As a manganese donor low-carbon ferromanganese powder was used. Sintering was carried out in different atmospheres at 1120°C and 1250°C. After sintering, investigated steels were subsequently tempered at 200°C for 60 min in air. The results of statistical analysis show, there is the relationship between mechanical properties versus processing parameters.

Abstract: Conventional convex hull algorithm determines the smallest convex polygon that contains the analyzed shape. The article presents a modification of this algorithm, which allows us to select the concavity to detect. In contrast to the typical convex hull algorithm, the data are analyzed in portions. This paper proposes the use of this modified algorithm for the defects detection on medical images. Two types of images were used: micro-computer tomography images of dental root canals filled with sealer and magnetic resonance images of a patient hand with rheumatoid arthritis. Those images contained some defects that needed to be measured. Prepared algorithm greatly facilitated this process by supporting the user in the segmentation process. The achieved results were positively evaluated by experts - doctors: rheumatologists and endodontists.

Abstract: The paper presents the influence of low cycle fatigue (LCF) on the changes in microstructure of GX12CrMoVNbN9-1 cast steel after the 1040°C/12h/oil + 760°C/12h/air + 750°C/8h/furnace heat treatment. The examined cast steel was subjected to LCF at room temperature and at 550°C under the conditions of controlled total strain. It was observed that fatigue life of the cast steel decreased with increasing temperature. Cyclic softening was noticed at all temperatures. TEM quantitative characterization of the microstructure after LCF was carried out using: mean diameter of subgrains, density of dislocation and mean diameter of M₂₃C₆ carbides. For the mean diameters of subgrains and M₂₃C₆ carbides parameters, the histograms were made using STATISTICA 9 software. The research of quantitative parameters of the microstructure was carried out using AnaliSIS programs. Performed research of the quantitative parameters of microstructure has shown that the decrease in fatigue life with the temperature rise and cyclic softening of the cast steel after LCF are related to an increase in the lath width, the change from lath structure to cell/equaixed substructure, a decrease in dislocation density by the recovery process and a growth of M₂₃C₆ carbides.

Abstract: The GX12CrMoVNbN9-1 (GP91) cast steel belongs to a new group of high-temperature creep resistant cast steels being introduced to the power industry. The cast steel is characterized by higher mechanical properties in comparison with the low alloy Cr – Mo or Cr – Mo – V cast steels used so far. The mechanical properties of martensitic cast steels depend on the parameters of heat treatment, such as the temperature of austenitizing. The paper is to present the results of research on the influence of austenitizing temperature ranging from 980 to 1100oC and hold time of 12 hours on the growth of austenite grain. The tests were carried out on test samples taken from a test coupon. Description of the influence of austenitizing temperature on the austenite grain size was made using the mean diameter of grain. Performed tests have shown that the distributions of mean diameters are of normal character, on the significance levels α = 0.05 and α = 0.04. For the investigated temperature range, the ν coefficient of non-homogeneity of the mean diameter of prior austenite grain was determined. The achieved results have proved that in the temperature range of 1010 to 1070°C the mean diameters stay within the same grade of grain size and the considerable grain growth is visible at the temperature of 1100°C.