Materials Science Forum Vol. 1166

Abstract: The origin of the thermal creep of zirconium cladding tubes in all light water reactors is still the subject of deep confusion and intricate controversies. The reason for this inconvenient situation is obviously that microstructural processes in thermal creep remain poorly understood and this is due to the relatively small number of studies that have been carried out. In this study uniaxial creep tests in tension of zirconium alloy cladding tubes in the as-received and pre-hydrided states are followed by metallographic analysis of the as-received and crept specimens by light microscopy and SEM to explain the observed high-temperature creep behavior of the tubes.

Abstract: The creep behaviour of new grades of austenitic creep resistant steels used mainly for USC boiler superheaters reflects the development and degradation of microstructure with respect to changes that occur during long-term creep exposure. This mainly involves the formation of a brittle intermetallic σ-phase, which significantly affects mechanical properties, creep rupture strength and creep plasticity. The paper describes the creep cavitation damage of heterogeneous TIG weld joints of tubes made of HR3C steel and Inconel 617 alloy welded with Inconel 617 alloy-based welding wire, that were tested by internal pressure creep test. The final damage always occurred in HR3C steel beyond the heat-affected zone of the weld joint. Creep cracks propagated along grain boundaries decorated with M₂₃C₆ carbides and also sigma phase. The extent and range of creep cavitation damage was evaluated according to the NORDTEST TR 302 procedure (hereafter referred to as NT TR 302).

Abstract: Burning fossil fuels releases greenhouse gases into the atmosphere, causing global warming and climate change. Reducing climate impacts can be achieved by switching to carbon-free energy sources, and hydrogen as a carbon-free energy carrier can be a key parameter. The use of a mixture of natural gas and hydrogen is a much-discussed option. The use of this mixture in industry, e.g. as fuel for gas-fired power plants, would lead to a lower environmental burden due to reduced greenhouse gas emissions. Efficient and economically acceptable distribution of hydrogen is important. The best option is to transport the gas using existing pipeline systems. Hydrogen degrades the mechanical properties of most structural metal materials, especially steel. Describing the degradation of materials exposed to a hydrogen environment is a key parameter for the use of existing natural gas transport infrastructure. For the experiment, X52 steel was used, which is the base material for the natural gas distribution network. Electrolytic saturation was used to charge the material with hydrogen. Different saturation times were tested. The mechanical properties were determined by the notch impact test.

Abstract: This paper deals with results of detailed investigations on a failed cast upper ram (63 tons) of a die-forging hammer. Subsurface cast defects primarily represented the “weak areas” responsible for the initiation of fatigue cracks during industrial exploitation. These defects mostly corresponded to gas bubbles. The occurrence of Ti (C,N) particles on the surface of these bubbles indicated that these defects were probably a consequence of release of gas products from the casting mould and/or mould's painting during the pouring of liquid metal. The evidence of fatigue initiation on repair welds was obtained only in one case. It was revealed that in this case the cast defects on the surface of the guiding radius were not completely cut off before repair welding. The remnants of the cast defects in the interface weld/base material initiated the fatigue crack. Basic mechanical properties of the subsurface layer of the upper ram complied with the design requirements.

Abstract: The aim of the work was to assess the nature and causes of defects – cracks in the welds of membrane wall panel tubes (MW) of a thermal power plant boiler made of T24 steel. This steel is intended to produce MW evaporators and superheaters for power plant units operating in the area of supercritical steam conditions. Its advantage, compared to the originally used materials, is higher creep resistance. The main expected advantage of the steel was to obtain optimal properties of welded joints without subsequent post-weld heat treatment (PWHT).

Abstract: Ballistic steels are used for the basic ballistic protection of armoured vehicles against the compressive energy of exploding munitions and the impact energy of projectiles fired from small arms. Steels with hardness up to 500 HBW are used to protect the chassis of armoured vehicles. Steels with a hardness greater than 500 HBW are used to protect the cabs and turrets of armoured vehicles. Ballistic steels belong to the class of low alloy high strength steels where a good combination of high strength and toughness is required. Higher strength is achieved in the final production process which involves heat treatment by quenching and tempering. This treatment creates a martensitic structure. Another heat treatment option is the Q-P (quenching and partitioning) process, where higher material strengths can be achieved in some steels while maintaining ductility. This paper focuses on a comparison of the microstructure as observed using a light microscope of the ballistic steel Secure after heat treatment by the manufacturer and after heat treatment by the Q-P process. It was found that the Q-P process produces a finer grained structure and a change in mechanical properties due to the stabilised austenite and strained martensite in the microstructure of the ballistic steel.

Abstract: This study presents a comparative analysis of manufacturing techniques for 316L stainless steel, focusing on Direct Energy Deposition (DED) and traditional casting methods. The research aims to evaluate the differences in microstructure, mechanical properties, and overall performance of components produced by these two distinct processes. Through a series of experiments and material characterizations, including microscopic examinations and mechanical testing, we investigate how the manufacturing techniques influence the final properties of 316L stainless steel. Our findings reveal significant variations in grain structure, porosity, and tensile strength, highlighting the advantages and limitations of each method. This comparative study provides valuable insights for industries seeking to optimize their manufacturing processes for high-performance applications, ultimately contributing to the advancement of additive manufacturing technologies and traditional casting techniques.

Abstract: In the presentation will be presented different additive 3D printing techniques for obtaining different plastic parts using the additive technology. The processes are Stereolithography and Fused deposition modelling After choosing the two processes, the next step is choosing the best material that will have the needed properties. The goal of this paper is to obtain a better gear with improved properties, resistance, and durability. The obtained probes will be tested with a traction device and resilience of the gear. The two parts will be compared, and the best obtained part will be chosen comparing part properties and the production cost

Abstract: Pyrolytic technology was developed to grow Zn-based nano- and microstructures. It was based on the application of a mixture of ammonium chloride, Zn and ZnO powders as source materials. Two temperature profiles were used for the synthesis. In the first and second growth processes, the maximum substrate temperatures of 250 and 410°C were reached, respectively. The granular layer of micrometer range ZnO crystals was produced in the first process. By depleting the source with NH₄Cl, the Zn polyhedra, and layered spheres were produced within 50–65 min in the second process. By increasing the NH₄Cl content in the source to 0.9 g, the Zn/ZnO core–shell spheres were synthesized. The further increase of process duration led to the out-diffusion of Zn from the core, its oxidation, and the formation of a thick, dense ZnO spherical shell. Even further annealing in residual gases caused the increase of the Zn vapor pressure inside the shell. As a result, at a certain Zn vapor pressure, the shell bursts, causing the formation of a hollow ZnO microsphere.