Yasuhiro KAMADA
Iwate Univ, Morioka, Japan

Application of magnetic hysteresis loop measurement for assessment of microstructure modification of thermally aged and neutron irradiated iron-chromium alloys

Iron based chromium alloys are used for structural components in fossil and nuclear power plants. Since thermal and radiation exposure cause materials embrittlement, it is important to develop NDT methods for the safe and reliable operation. The purpose of this study is to clarify the thermal aging and irradiation effects on microstructures and magnetic properties of Fe-Cr alloys and discuss a feasibility of MHL methods.

Dariusz MĘŻYK
Energy Institute, Warsaw

Operation of high pressure pipelines after exceeding of their design period of exploitation

The current long-term operation of energy blocks is connected with work in conditions of changeable stress and temperature fields. Construction materials of pipelines are exposed to the impact of environment of gasses and liquids and to the effect of mechanical loads. These factors cause degradation of the microstructure in the operating period and as a result lead to worsening of mechanical properties. Cracking of welded joints and breakdowns of shaped elements of thermal instalations and energy pressure facilities are an effect of the increase of stresses. Considering parameters of work one should take particular diagnostic care of the high-pressure pipelines. Correctly conducted diagnostic process has a direct impact on the safety and reliability of the operation of energy facilities. One take particular diagnostic care of the high-pressure pipelines due to their exceptional character. High temperature – in the scope of temperatures of 540oC, pressure values reaching up to 20 MPa cause that elements from which the installation is constructed are not always able to transfer loads and the pipelines can get damaged. A very significant problem occurring during the operation of energy devices is a mutual influence of the pipeline-turbine system. Apart from stresses from internal pressure and temperature stresses also mechanical loads coming from the weight of the pipeline and fittings mounted on it and coming from restricted ease of thermal dilatation and the quality of work of the fasteners system have an influence on strains of pressure elements. Due to the working conditions and the loads connected with them the most significant are initial steam pipelines and mainly their shaped elements (elbows, tees, cross-overs, steam mixers, main valves).

Dominik KUKLA
Institute of Fundamental Technological Research

Evaluation and classification of grinding burns by eddy current method

The paper presents the results of research on the assessment of the possibility of identification and quantitative description of local changes in properties in the material of hardened layers caused by grinding burnings. For this purpose, a series of defects was prepared on AISI 9310 material, using laser techniques imitating grinding burns. These burn marks were characterized in terms of changes in microstructure and hardness on the surface of the scorched sample and cross-sections. On this basis, the depth of exposure to the heat zone from the grinding tool was evaluated. The sample with three burns, obtained for various parameters of the laser beam, was subjected to the eddy current tests for the quantitative description of the signal from each of the defects. This test was performed in the sample scanning mode with a pencil probe. The effects, in the form of variable values of both the amplitude and the phase angle of the signal from three defects, indicate the possibility of identifying burns along with their quantitative description. On the basis of the magnitude of the amplitude of the indication for each defect, it is possible to estimate its size (depth). However, differences in the magnitude of the phase angle of the signal may indicate the degree of superheat of the sample in the area of induction of eddy currents. However, changes in hardness profiles made on cross sections are difficult to relate to results obtained with eddy currents due to the difficulty of estimating the depth of their penetration into the ferromagnetic material of the tested samples.

VSB – Technical University of Ostrava, Ostrava, Czech Republic

Research of 313L metallic powder for use in SMM 3D printing

3D metal printing is an increasingly popular production of steel parts. The most widespread and most accurate method is SLM (Selective Laser Melting), which uses metallic powder as the input material. The article is dedicated to researching the supplied powder from Renishaw. The powder is made by gas atomization and 3 phases of powder (virgin, sift and waste) that are present in the SLM process are examined. Powder morphology by SEM electron microscopy is investigated and the porosity of the powder is measured by optical method. Next, the powder fraction is examined. In conclusion, there are recommendations and other directions of possible research. From the research conducted and the results obtained using experimental investigation we can recommend the following measures to achieve the best possible consolidation: as spherical particles as possible, fine surface, as few satellites as possible (satellite – surface irregularity, smaller particles adhered to the surface of a larger particle), low internal porosity, as few surface pores as possible, tight distribution of particles, high purity.