Z. Nitkiewicz

The X-Ray Measurement of the Thermal Expansibility of Al-Si Alloy in the Form of a Cast and a Protective Coating on Steel

The paper presents the investigation of the expansibility of an Al-Si alloy in the form of a protective coating applied on a steel substrate and as a conventional cast, respectively. Examinations were carried out in the temperature range of troom÷220°C using the diffractometric technique based on reflections (311), (222), (400), and (331) from the Al solid solution. It was demonstrated that the coating exhibited better thermal expansibility compared to the cast, and its thermal expansion coefficient was close to the standard values for alloys of the same chemical composition. For the cast, the thermal expansion coefficient was lower by approx. 25% in relation to the standard value. It was also found that the soaking of alloys during X-ray examination reduced their texturing and caused changes in the microstructure of both the coating and the cast by thinning the silicon crystals and rounding their edges.

Structural Analysis of Sintered Materials Used for Low-Temperature Fuel Cell Plates

Bipolar plates (BPs) are key components of fuel cells. Functions of materials used for fuel cells include equal distribution of gas fuel and air, conduction of electricity between adjacent cells, heat transfer from the cell as well as prevention of gas leakage and cooldown. Moreover, the material must show particular corrosion resistance in cell’s working conditions. Meeting particular requirements or prevention of the abovementioned situations will enable efficient operation of cells. Due to multifunctional nature of fuel cell plates, choice of materials used for plates is immensely difficult. This paper presents opportunities of application of a new technology of powder sintering for creation of parts for electricity and heat generators. This work also presents analysis of structural and phase-related properties, porosity and strength tests.

Texturing of Magnetite Forming during Long-Term Operation of a Pipeline of 10CrMo9-10 Steel

The paper presents results of X-ray measurements of the texture of a magnetite (Fe3O4) layer formed on 10CrMo9-10 steel during 100,000 hours operation at the temperature of 575°C (in a flowing medium environment). The formed oxide layer was ≈140µm thick. Measurements of texturing were performed on the oxide surface and also at the depth of ≈50µm from the surface (1st polishing) and ≈100µm (2nd polishing). X-ray studies were carried out using the radiation of a cobalt anode tube, λCo=0.17902nm, for (311) and (400) Fe3O4 reflections, using a radiation beam collimated to φ=2mm. The study was aimed at determination of correlation between the texturing and the structure on the magnetite layer cross-section. A clear texturing of {111} and {111} type for the magnetite in the initial state and after the second polishing was found. Instead, after the first polishing there was a substantial texturing of {034} and {015} type. A different nature of the texture may result from a diversified morphology of magnetite at various depths (caused inter alia by a differentiated temperature on the tube wall cross-section during the material operation), which is related among other things to the crystallites size. The magnetite structure and texture changes can affect the magnetite porosity and cleavage.

Structural Analysis of Hydroxyapatite Sinters with Addition of ZrO2 Phase

A range of benefits of implants containing hydroxyapatites results, among other things, from their phase composition and degree of porosity. Poor mechanical properties of hydroxyapatite (HA) ceramics considerably limit its wider use. One of the methods for improvement of poor HA properties is addition of solid solution of Y2O3 in ZrO2. [1-8]. The investigations focused on compositions of ceramic powders based on hydroxyapatite with addition of zirconium dioxide (ZrO2 + 8%wt. Y2O3 and ZrO2 + 20%wt. Y2O3). The powders were axially compacted and then sintered at the temperature of 13000C for two hours. After the process of sintering the samples were subjected to analysis of microstructure, phase composition and geometrical measurements in order to determine volume density in each sample.

Corrosion Resistance of Sinters CNT-Cu/Cu

Copper and its alloys are used in many industrial and marine applications due to their good heat transfer and electrical properties. Copper is, however, susceptible to many forms of corrosion, including localized corrosion, such as crevice corrosion. The paper presents the preliminary results of studies on obtaining copper-based composite materials strengthened with carbon nanotubes modified with copper nanoparticles. The nanotubes modification was carried out by chemically attaching copper nanopaticles originating from copper acetate. Electrolytically obtained copper powders were used as the matrix. The materials were consolidated by one-sides pressing followed by sintering. One of the important property of these materials is its resistance to corrosion. Potentiokinetic investigations in a 3.5% NaCl solution were performed on specimens of different CNTs content. Determined what influence on the corrosive changes has the addition of nanotubes to copper.

Analysis of Textures of Wires Drawn in Pressure and Roller Dies with ODF

In the work orientation distribution functions (ODF) were determined for wires drawn in pressure and roller dies from a high carbon steel wire rod with a diameter 5.5 mm to wires with a diameter 3.8 mm and 3.0 mm. For a comparison ODFs for wires drawn conventionally were also determined. The texture was measured on the cross sections of investigated wires prepared in a form of squares to eliminate the effect of the surface layer. In the first stage of a drawing with a total reduction of 54.3% it has been found that in wires drawn conventionally (KI), in pressure dies (HI) and in roller dies (RI) a strong <110> fibre-texture exist with a value of the ODF equal to about 3.2 for all tested wires. At an increase of the total reduction from 54.3% to 71.5% values of ODF were different for different methods of drawing. For wires with a diameter 3.0 mm drawn conventionally (KF) it was equal 4.25 and for wires drawn in pressure dies (HF) the ODF value was the highest and equal to 4.4. For wires drawn in roller dies the ODF value was the lowest and equal only to 2.6. It means that in spite of the increase of the total reduction roller die drawing results in a decrease of the sharpness of the fibre texture <110>. In conventional drawing and in pressure dies drawing an increase of the <110> texture has been noticed with the increase of the total reduction. In addition to a strong <110> texture component, specimens K and H also featured weak <311> and <310> components. In R specimens there were more of such additional components after the first stage of drawing i.e. <311>, <310>, <210>, <211> and after the second stage of drawing (total area reduction 71.5%) - <311>, <310>.