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B. Leszczyńska-Madej and M. Madej

The Properties of Babbitt Bushes in Steam Turbine Sliding Bearings

The analysis of the properties of babbitt bushes is presented in this article. Materials intended for examinations were charged from the TK-120 steam turbine of TG-8 turbosystem from the Power Station Stalowa Wola. The specimens were subsequently tested for Brinell hardness, microhardness, bending strength and wear resistance. The wear tests were carried out using the block-on-ring tester. The samples were also investigated by means of both light microscopy (LM) and scanning electron microscopy (SEM).

Open access

B. Leszczynska-Madej

Attempts have been made to describe the influence of sintering temperature on the microstructure and properties of Al - SiC composites. Mixtures of 100%Al and Al - 5% SiC, Al - 10% SiC were produced by tumbling for 30 minutes in the Turbula T2F mixer. The powders were subsequently cold pressed at pressure 300MPa in a rigid die on a single action press. The green compacts were sintered in nitrogen at 580°C and 620°C for one hour. The main objective of this work was to determine influence of chemical composition and the manufacturing parameters on microstructure and properties of Al - SiC composites produced by powder metallurgy technology.

Open access

B. Leszczyńska-Madej, P. Pałka and M. Richert

Abstract

Polycrystalline aluminium Al99.5 was deformed through the combination of equal-channel angular pressing (ECAP) by B route (4, 8 and 16 passes) and then by the hydrostatic extrusion (HE) using the cumulative way of deformation, just to the achieving the final wire diameter d = 3 mm. The microstructure of samples was investigated by means light microscopy (LM). Additionally the microhardness measurement and the tensile test were performed to determine the level of aluminium hardening. The texture was determined by using the Brucker Advance D8 equipment.

The aim of the research was to determine the influence of severe plastic deformation exerted in the process of equal-channel angular pressing (ECAP) and hydrostatic extrusion (HE) on the microstructure and properties of polycrystalline aluminium Al99.5.

The microstructure observations both after the HE process and the combination of ECAP + HE revealed the elongated to the extrusion direction grains and numerous bands and shear bands. The bands and shear bands most clearly revealed at the perpendicular section. The performed investigations showed that with the increase of the deformation the aluminium level hardening increase. The highest properties of tensile strength - UTS = 218 MPa and microhardness level HV0.1 = 46 were obtained after 8 ECAP + HE.

Open access

B. Leszczyńska-Madej and M. Madej

Abstract

The results of tribological tests and microstructure examinations of tin babbit with 1.5 % Pb addition after heat treatment are presented in this paper. The specimens were annealed at 150°C for 2, 8, 24 and 48 hours and then tested for wear resistance and Brinell hardness. The wear tests were carried out using a block-on-ring tester operating under dry and wet conditions. The samples were also investigated by light microscopy (LM) and scanning electron microscopy (SEM).

Open access

M.W. Richert, B. Leszczyńska-Madej, W. Pachla and J. Skiba

The changes of Al99.5 microstructure and properties deformed by hydrostatic extrusion process in the conditions of constant strain rate (1.35×102s-1) and variable deformation (φ = 1.44÷2.85) were investigated. The samples were investigated by means both optical (LM) and transmission electron microscopy (TEM). The size of subgrain was statistically measured by mean chord. To establish the influence of hydrostatic extrusion on the properties of the polycrystalline aluminium Al99.5, the microhardness was measured and the tensile test was performed.

The bands and shear bands were the characteristic feature of the sample microstructure. TEM micrographs show equiaxed subgrains with small density of dislocations inside. The measured subgrain size was placed in the range of d = 550÷650 nm. The mechanical properties of polycrystalline aluminium Al99.5 keep almost the same level in the investigated range of deformations. It was found that after the initial deformation microhardness and yield stress nearly twice increase in comparison to the initial state. The greatest increase of properties was observed after deformation φ = 1.44. Then the mechanical properties stabilize.

Open access

B. Leszczyńska-Madej, A. Wąsik and M. Madej

Abstract

A conventional powder metallurgy method (PM) was used to produce Al-SiC and Al4Cu alloy matrix composites with 2.5, 5, 7.5 and 10 wt% of SiC particles. Two different sizes of the reinforcing phase particles were applied to determine their effect on composite microstructure. The sintering process was carried out at 600°C under nitrogen atmosphere, and its consequence was the appearance of aluminium nitrides in composite microstructure acting as an additional strengthening phase. The composites were next re-pressed and re-sintered (2p2s) under the same conditions. The main aim of this article was to examine the microstructure of the SiC reinforced Al and Al4Cu alloy matrix composites. To achieve this goal and characterize the sintered materials, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques were used.

Open access

B. Leszczyńska-Madej, M.W. Richert and M. Perek-Nowak

Abstract

Processes of severe plastic deformation (SPD) are defined as a group of metalworking techniques in which a very large plastic strain is imposed on a bulk material in order to make an ultra-fine grained metal. The present study attempts to apply Equal-Channel Angular Pressing (ECAP), Hydrostatic Extrusion (HE) and combination of ECAP and HE to 99.5% pure aluminium. ECAP process was realized at room temperature for 16 passes through route Bc using a die having an angle of 90°. Hydrostatic extrusion process was performed with cumulative strain of 2.68 to attain finally wire diameter of d = 3 mm. The microstructure of the samples was investigated by means of transmission and scanning electron microscopy. Additionally, the microhardness was measured and statistical analysis of the grains and subgrains was performed. Based on Kikuchi diffraction patterns misorientation was determined. The measured grain/subgrain size show, that regardless the mode of deformation process (ECAP, HE or combination of ECAP and HE processes), grain size is maintained at a similar level – equal to d = 0.55-0.59 μm. A combination of ECAP and HE has achieved better properties than either single process and show to be a promising procedure for manufacturing bulk UFG aluminium.

Open access

B. Leszczyńska-Madej, M. W. Richert, I. Nejman and P. Zawadzka

Abstract

The present study attempts to apply HE to 99.99% pure copper. The microstructure of the samples was investigated by both light microscopy and scanning transmission electron microscopy (STEM). Additionally, the microhardness was measured, the tensile test was made, and statistical analysis of the grains and subgrains was performed. Based on Kikuchi diffraction patterns, misorientation was determined. The obtained results show that microstructure of copper deformed by hydrostatic extrusion (HE) is rather inhomogeneous. The regions strongly deformed with high dislocation density exist near cells and grains/subgrains free of dislocations. The measurements of the grain size have revealed that the sample with an initial in annealed-state grain size of about 250 μm had this grain size reduced to below 0.35μm when it was deformed by HE to the strain ε=2.91. The microhardness and UTS are stable within the whole investigated range of deformation.

Open access

A. Woźnicki, D. Leśniak, G. Włoch, B. Leszczyńska-Madej and A. Wojtyna

Abstract

The paper presents the results of laboratory homogenization investigations of the 6082 grade alloys, differing in Mg and Si content. At the first stage, the microstructure of alloys was analysed after homogenization finished with water quenching. SEM/EDS investigations and DSC tests were applied to evaluate the dissolution of the Mg2Si particles and concentration of the main alloying additions in the grains interiors, depending on soaking conditions. In the case of alloy with lower Mg and Si content, homogenization the temperature of 535ºC for 8h is sufficient for significant Mg2Si particles dissolution. For the alloy with higher Mg and Si content, after homogenization the temperature of 550ºC for 8h, the amount of undissolved Mg2Si particles decreases visibly, compared to homogenization at 535ºC for 8h. However, an unfavourable tendency of dispersoids growth is observed and these soaking conditions are not found to be recommended.

At the second research stage, the influence of homogenization cooling rate on the size and distribution of the Mg2Si particles observed in the alloys microstructure was analysed. The ability of the Mg2Si particles, precipitated during various homogenization coolings, to rapid dissolution was estimated. For this purpose, the hardness after solution heat treatment with short annealing and ageing was determined and the DSC tests were performed. It was found, that cooling after homogenization at 315ºC/h is sufficient for precipitation of fine Mg2Si particles, which dissolve during subsequent rapid heating. Cooling at 40ºC/h, causes precipitation of Mg2Si phase in the form of large particles, unable for further fast dissolution.

Open access

A. Woźnicki, D. Leśniak, G. Włoch, P. Pałka, B. Leszczyńska-Madej and A. Wojtyna

Abstract

The influence of cooling rate after homogenization on the 2017A alloy microstructure was analysed. The capability of the θ (Al2Cu) particles, precipitated during various homogenization coolings, for rapid dissolution was estimated. For this purpose, the DSC test was used to determine the effect of the cooling rate after homogenization on the course of melting during a rapid heating. Moreover, the samples after solution heat treatment (with short time annealing) and ageing, were subjected to the microstructure investigations and the microhardness of grains interiors measurements. It was found that cooling after homogenization at 160 °C/h is sufficient for precipitation of fine θ phase particles, which dissolve during the subsequent rapid heating. The cooling at 40 °C/h, causes the precipitation of θ phase in the form of large particles, incapable of further fast dissolution.