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.

Prolongation of the service life of key components of fossil-fuelled power plants beyond their original design limit must be accompanied by thorough and extensive monitoring of the actual material state and particularly creep damage. The extent of cavitation is nowadays routinely tested in-situ by using replica method and its quantification is based on practices stated in VGB-TW 507, NORDTEST NT TR 302 derived from the original Neubauer's classification of cavitation damage. Evaluation of cavitation damage based on the measurement of the number of cavities and/or creep micro-cracks has become a routine activity, but in cases when steel contains large amount of non-metallic inclusions, they can be wrongly identified as cavities and to invalidate the result of calculation of cavitation damage. Comparative analysis of cavitation damage was performed in a pipe bend and its weldment made of a low-alloy 0.5Cr-0.5Mo-0.3V steel creep exposed at 540 °C for more than 225,000 hours by using OM (SEM) and replica method and revealed the comparative extent of cavitation damage decreasing from the outer to inner surface of the pipe wall.

The paper deals with research, development and verification of production technology of selected welded joints for pressure vessels located in primary circuit of nuclear power plants type MIR 1200. Effects of various welding technologies on mechanical and fracture properties were studied. Four types of weld joints made of 10GN2MFA steel grade were prepared for experimental programme consisted of testing of conventional mechanical (tensile and impact tests) as well as fracture toughness and low-cycle fatigue tests and also stress corrosion cracking test in water environment. Effect of elevated operating temperature on material properties was evaluated, too.

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.

The quality production technology for the WNr. 1.8504 steel was developed. The aim of the work was to achieve the required internal micro-purity and determine the effects of different production technologies on the qualitative parameters of forged-steel pieces. Firstly, polygonal ingots weighing 1600 kg were produced, using the metallurgical units, in a controlled-atmosphere induction-melting furnace (IF) without vacuum treatment, and in a vacuum and pressurized induction-melting furnace (VPIM) with vacuum treatment. The ingots were subsequently reshaped by open-die forging into bars with a rectangular cross-section. The effect of the ingot-production technology was evaluated by comparing the forged-steel pieces in terms of their purity, macrostructure and microstructure. Keywords: vacuum, inclusion, aluminium, steel Izvr{en je bil razvoj kakovostne proizvodne tehnologije jekla W.Nr. 1.8504. Namen je bil dose~i`eleno notranjo mikro~isto~o in ugotoviti vpliv razli~nih tehnologij proizvodnje na kvalitativne parametre odkovkov. Najprej so bili izdelani poligonalni kovani ingoti z maso 1600 kg, z uporabo naslednjih metalur{kih agregatov: v indukcijski talilni pe~i s kontrolirano atmosfero (IF) brez vakuumskega rafiniranja in v vakuumski ter indukcijski talilni pe~i (VPIM) s povi{anim tlakom in z vakuumskim rafiniranjem. Nato so bili ingoti s prostim kovanjem preoblikovani v palice s pravokotnim prerezom. Vpliv tehnologije proizvodnje ingotov je bil ocenjen s primerjavo odkovkov z vidika~istosti, makro in mikrostrukture.