Volume 14 (2014): Edition 4 (December 2014)

The results of a microstructure examination and mechanical properties of 15HM (13CrMo4-5) steel are presented in the article. The examined elements are the samples taken from the live steam pipeline serviced for about 420 000 hours at the temperature of about 510°C, and pressure of 11 MPa. It has been shown that after long-term operation the examined steel has a ferritic-pearlitic microstructure with a dominant content of quasipolygonal ferrite. The processes of fragmentation of lamellar precipitates and their spheroidization were observed in pearlite. On the grain boundaries, single lamellar precipitations were observed. Moreover, numerous precipitations at the interface of three grain boundaries were revealed. The examined steel, despite its long-term service time, was characterized by the strength properties (YS, TS) slightly lower than the required minimum, the impact energy value KV equal to 20 J, and the transition temperature shifted to a temperature above zero. Relatively low level of degradation of the microstructure and mechanical properties of the investigated steel can result from high stability of the ferritic-pearlitic microstructure.

The electrochemical formation of oxide nanotubes on the Ti6Al4V alloy has been so far difficult due to easy dissolution of vanadium reach β-phase of the two phase material. Due to the topographical heterogeneity of the anodic layer in nano and microscale at anodizing of the Ti6Al4V alloy we focused to establish the relationships between nanotube diameters on both phases of the alloy and fluorides concentration in electrolyte. We studied the effect of fluoride concentration (0.5-0.7 wt.%) in 99% ethylene glycol on morphological parameters of nanotube layer on the Ti6Al4V alloy anodized at 20V for 20 min. Nanotubes with diameter ~40-50 nm ±5nm on the entire Ti6Al4V alloy surface in electrolyte containing 0.6% wt. NH4F were obtained. Microscale roughness studies revealed that nanotubular layer on α-phase is thicker than on β-phase. The annealing of nanotube layers at 600°C for 2h in air, nitrogen and argon, typically performed to improve their electrical properties, influenced chemical composition and morphology of nanotubes on the Ti6Al4V alloy. The vanadium oxides (VO2, V2O3, V2O5) were present in surface nanotube layer covering both phases of the alloy and the shape of nanotubes was preserved after annealing in nitrogen.

Evaluate of the usefulness and reliability of structures based on the analysis of recorded parameters determining the flow through the Human Aortic Bioprosthesis (HAB) have been dealt with. By flow parameters changes determining the performance environment of prosthesis analyzed change of the motion dynamics of the valve leaflets as a function of pressure, thereby determining the degree of alignment of the prosthesis to the performance conditions. Based on the gathered measurement data a comparative analysis of flow rate valve prostheses for different frequency values of the piston pump imitating the heart, different ejection capacity and pressure conditioning work environment prosthesis were studied. Interpretation of the recorded image gave the basis for determining the Effective Orifice Area (EOC).

The goal of the research was to evaluate the change of displacement/strain phases in the P91 steel under static load conditions. Undertaken tests were aimed at estimation and analysis of the impact of the material state, which was subjected to loading conditions, on the distribution of stress pattern using ESPI system. Specimen made of high temperature creep resistant steel X10CrMoVNb9-1 (P91) used as a construction material for boiler steam feed heaters, vapor tanks, pressure vessels and vapor pipelines, is used in the service conditions of temperature range up of 650°C. Test samples were taken from two P91 steel pipes. One sample came from a segment of a pipeline transporting fresh vapor in time 80 000 h, under the pressure of 8.4 MPa and temperature 540 °C. The second sample was the same material but in the delivery state.

The aim of the study was to determine the microstructure and residual stress changes which appears in the S235 steel (which is designed for operating in elevated temperatures) during cold rolling. The changes of orientation, both morphological and crystallographic, are occurring as a result of the rolling process. Analysis of the results allowed to determine the change in grain morphology (size, shape), determination of grain morphology of the rolling direction and determination of crystallographic texture. The dislocation density present in the material before and after the cold rolling process was estimated on the basis of dislocation structure images obtained via transmission electron microscope. The observed microstructural changes were correlated with the results of nondestructive testing using eddy current method. They allowed for the identification of the state of stress measured on three different surfaces of the rolled sheet (parallel and perpendicular to the rolling direction). As the result the usability of using the non - destructuve techniques of stress level determination was proved.

Copper Oxide is an extensively studied group II-VI semiconductor with optical properties. It exhibits a wide variety of morphologies in the nano regime that can be grown by tuning the growth habit of the CuO crystal. CuO nano materials with an average particle size of 15-27 nm are synthesized by chemical route. XRD, SEM, FTIR UV-Vis and EDS characterize the samples. The percentage of doping material is confirmed from the EDS spectra. The average crystal size of the prepared CuO: La nanopowder is determined by XRD. The UV absorption spectra revealed the absorption edge at wavelength 389 nm indicating the smaller size of CuO:La nano particle. The optical direct band gap energy of doped CuO nanoparticle is found to be in the range 3.149 eV. The increasing red shift with decreasing particle size suggests that the defects responsible for the intra gap states are primarily surface defect. The La doped CuO is highly effective and can significantly enhance the photo catalytic degradation.

This study examined effect of inclusion of expanded graphite (Exp-G) on morphology, thermal, mechanical and flame retardant properties of PS, nitro-substituted polystyrene (N-PS) and amino-functional polystyrene (A-PS). FESEM showed exfoliated sheet morphology due to intercalation of N-PS and A-PS in expanded galleries. Tensile strength of A-PS materials (31.5-56.9 MPa) was higher than PS and N-PS. 10 % weight loss of A-PS nanocomposites (482-518 °C) was higher relative to pristine polymer and other nanocomposites. Cone calorimetry results revealed that there was lowering in PHHR of A-PS nanocomposites with 0.5 wt.% filler (428 kW/m²), while PS nanocomposites showed PHHR of 443 kW/m².

New materials obtained by pyrolysis of gelatine (G) and poly(1,2-dimethylsilazane) (PSN) (weight ratio: G/PSN 70/30) at temperatures 700 and 900 °C were characterized by SEM and Raman spectroscopy. The presence of ceramics influences on the cluster size of the materials. Electrochemical tests were performed by cyclic voltammetry and galvanostatic cyclic polarization. The capacity of G/PSN was 464 and 527 mAh/g for materials pyrolysed at 700 and 900 °C. The capacity fading was 1 % after 17^th cycle for G/PSN at 900 °C. This value is higher of 185 mAh/g in comparison to capacity of gelatine pyrolysed at the same conditions.

Alloy and composite coatings are widely used in engineering, automotive and shipbuilding because of the possibility of improving the operational characteristics of the surface layer (mechanical, tribological, corrosion and decorative). The welding technology of applying alloy and composite coatings is widely used. The technology of infrasound thermal spraying of metal matrix composite coatings was presented. It is a simple technology and a very useful one in ship machinery regeneration during the cruise craft (e.g. internal combustion engines, torque pumps, separators). The metal matrix composite coatings must undergo finishing due to high surface roughness after application. Coatings obtained by thermal spraying have a large surface roughness, it is therefore necessary to make finishing coatings. Due to economic and technological developments it is essential that the coating was thin, abrasion-resistant, high smoothness, and the finishing was of chip that is not cause material loss. In order to ensure quality of technology offered the elements of the of machines used in shipbuilding of cold working by rolling, with small values of strain ratio, ultimately as a finishing alloy and composite coating is planned to use surface plastic forming of machine parts.

This paper presents an overview of the results of studies which, in addition to the detection of differences in the structure of the product and the thickness of the surface layers, aimed to diversify the signal from the stress changes caused by cracks, assess local defects in the microstructure deformed by heat treatment and detect hydrogen „in statu nascendi”. Measurements were performed using Wirotest 1000. Specialized probes were used to allow measurements on surfaces difficult to reach. Measurements were taken at different depths of penetration. Assessment of the correlation of eddy current measurements and microhardness was also performed.

One of the most important characteristics of the material allowing us to predict its applicability for specific tasks as a single object or as an integral part of the whole structure is the presence of stresses. There are many methods to measure stress. Among them, increasingly important and recognised as the most accurate non-destructive method is the X-ray measurement technique. The aim of this study was validation of the results obtained by the X-ray stress measurement method. Stress measurements were performed on samples of the three materials subjected during measurement to the effect of tensile forces. Studies revealed close relationship between the stress values measured by X-ray technique and actual values present in the examined material. The summation of residual stresses present in the material and stresses caused by the effect of external forces was observed.