The paper deals with the change of the structure and mechanical properties of the austenitic steels after the exposure at the critical temperature. The effects of the bend radius of tubes including effect of solution annealing on the mechanical properties and the structure were studied. The mechanical properties were studied using small punch test (SPT) and miniaturized tensile tests. From the results can be concluded that the mechanical properties and the structure have been influenced due to one year exposure at the working temperature significantly. Various amounts of σ-phase were found in the pulled part of the bend side of the tubes even after only thermal exposure without any loading. The effect of the heat treatment and the bend radius on the mechanical properties and the structure was also evident. Drop in fracture energy due to the presence of the σ-phase in the structure was clearly detected from force - displacement record of the small punch test. Keywords: Austenitic steels, bends, σ-phase, small punch test

The additive manufacturing (3D printing) of metallic materials is a relatively new technology and its use is quickly increasing. Although it is of interest to many researchers, there are still areas which are not fully explored. One of those areas is the behavior of large components and/or semi-products processed by 3D printing. This work is focused on the study of material properties of additive manufactured large block made of AISI 316L steel in two heat treatment conditions (as-printed and solution annealed) and their comparison with the properties of hot-rolled plate performed by tensile tests, Charpy V-notch tests, small punch tests and stress rupture tests. Mechanical tests were complemented by microstructural investigation and the fractographic analysis of fracture surfaces. We found out that mechanical and long-term properties of large 3D printed blocks of this steel are excellent and comparable with other published results obtained on small-sized and intentionally produced test pieces. The observed lower ductility is the result of printing imperfections in microstructure. The results of small punch tests confirmed the possibility of exploiting the existing database and using the correlation between small punch tests and tensile tests results even for 3D-printed AISI 316L steel.

The paper deals with research, development and verification of production technology of selected welded joints for pressure vessels of primary circuits of nuclear power plants of type MIR 1200. Effect of various welding technology including simulation heat treatment on mechanical and fracture properties have been studied. Four type of homogenous 10GN2MFA – 10GN2MFA type of welded joints have been prepared for experimental programme. Conventional mechanical properties (tensile and impact test) as well as unconventional mechanical properties (fracture mechanics, low-cycle fatigue and stress corrosion cracking in water environment) have been studied. Effect of elevated working temperature on structure and material properties has been evaluated. Temperature dependencies of shear fracture have been plotted and effect of welding procedure on transition temperature shift has been evaluated. Experimental data have been compared with numerical simulation using FEM.

This work is focused on the study of influence of additives manufacturing on material properties of AISI 316L steel. Comparison of the material properties of the plate produced by the selective laser melting (SLM) technology and the hot-rolled plate was performed not only on the results of tensile tests, but also on small punch tests, which is an evolving and promising testing method and will be implemented into standardized testing methods within EU soon. The determination of the yield point and the tensile strength from the results of small punch tests is based on the simple correlation among them. For wrought steels this correlation was verified but no such a relation is known for additive steels. Therefore, we tried to use this correlation to additive manufactured material and to compare the obtained results with the results of conventional tensile tests. The results of mechanical testing are complemented by microstructural investigation of both technologies, including fractographic analysis of fracture surfaces.

This paper is focused on evaluation of the plastic deformation effect, after the cold bending process for new austenitic material Super 304H designed for supercritical conditions. The aim of the project was to qualify the process of cold bending and then verify the properties of these bends in conditions approaching application. This paper presents the results of the plastic deformation effect on changes in the structure and mechanical properties at operating temperatures in corrosive environments coal combustion products and comparison to results before degradation. The tests were carried out on bends in two dimensions of tubes which are the most common sizes used in super-heaters for supercritical power plant boiler. The bends were produced by the method of cold bending on several bending radii in order to obtain information about the structure and behaviour of materials at various stages of deformation. To obtain reliable information tensile test, hardness test and metallographic examination were used on material from straight tubes of the bends and drawn parts before degradation and after degradation.