Maraging steel is a high-performance material valued for its exceptional properties, making it ideal for demanding applications such as aerospace, tooling, and automotive industries, where high strength, toughness, and precision are required. These steels can be prepared by powder metallurgy techniques, which offer new processing possibilities. This paper introduces novel thermal powder pre-treatment and its impact on the final mechanical properties. Solid solution pre-treatment results in a modest improvement in strength (from 972 MPa to 1000 MPa), while the use of pre-aged powder achieves the highest strength (1316 MPa) and lowest ductility (2.6%). A self-composite material is created by mixing pre-treated powders with the same chemical composition but different properties. Such material was characterized by intermediate strength (1174 MPa) and ductility (3.1%). Although challenges such a porosity and oxidation were present, this approach allows for tuning of mechanical properties by mixing pre-treated powders, offering significant potential for advanced engineering applications.

• Klíčová slova
• SPS, heat treatment, mechanical properties, powder metallurgy,
• Publikační typ
• časopisecké články MeSH

The present work describes the influence of different temperatures on mechanical properties and microstructure of additively manufactured high-strength 1.2709 maraging steel. For this purpose, samples produced by selective laser melting technology were used in their as-printed as well as their heat-treated state. Both samples were than exposed to temperatures ranging between 100 °C to 900 °C with a total dwell time of 2 h followed by water-cooling. The microhardness of the as-printed material reached its maximum (561 ± 6 HV0.1) at 500 °C, which corresponded to the microstructural changes. However, the heat-treated material retained its initial mechanical properties up to 500 °C. As the temperature increased, the microhardness of both the materials reduced, reaching their minimum at 900 °C. This phenomenon was accompanied by a change in the microstructure by forming coarse-grained martensite. This also resulted in a significant decrease in the ultimate tensile strength and an increase in the plasticity. TEM analysis confirmed the formation of Ni3Mo intermetallic phases in the as-printed material when exposed to a temperature of 500 °C. It was found that the same phase was present in the heat-treated sample and it remained stable up to a temperature of 500 °C.

• Klíčová slova
• TEM-analysis, annealing response, elevated temperatures, maraging steel, mechanical properties,
• Publikační typ
• časopisecké články MeSH

The main aim of this study was to determine the susceptibility of the additively manufactured high strength X3NiCoMoTi 18-9-5 maraging steel to hydrogen embrittlement. For this purpose, samples produced by selective laser melting technology, before and after heat treatment, were used. The examined samples were electrochemically charged with hydrogen in NaCl + NH4SCN solution at a current density of 50 mA/cm2 for 24 h. The H content increased from about 1 to 15 ppm. Heat treatment did not affect the amount of H trapped in the maraging steel. Tensile testing revealed that the tensile strength of the H-charged samples was much lower than that of the uncharged samples. Moreover, the material became brittle after charging compared to the ductile as-printed and heat-treated samples with elongation values of 7% and 2%, respectively. The loss of plasticity was confirmed by fractography, which revealed transformation of the fracture surface morphology from dimple-like in the as-produced state to a brittle one with smooth facets in the H-charged state.

• Klíčová slova
• hydrogen embrittlement, hydrogen-induced cracking, maraging steel, selective laser melting,
• Publikační typ
• časopisecké články MeSH

Powder metallurgy is a group of advanced processes for the synthesis, processing, and shaping of various kinds of materials. Initially inspired by ceramics processing, the methodology comprising of the production of a powder and its transformation to a compact solid product has attracted great attention since the end of World War II. At present, there are many technologies for powder production (e.g., gas atomization of the melt, chemical reduction, milling, and mechanical alloying) and its consolidation (e.g., pressing and sintering, hot isostatic pressing, and spark plasma sintering). The most promising ones can achieve an ultra-fine or nano-grained structure of the powder, and preserve it during consolidation. Among these methods, mechanical alloying and spark plasma sintering play a key role. This Special Issue gives special focus to the advancement of mechanical alloying, spark plasma sintering and self-propagating high-temperature synthesis methods, as well as to the role of these processes in the development of new materials.

• Klíčová slova
• mechanical alloying, powder metallurgy, self-propagating high-temperature synthesis, spark plasma sintering,
• Publikační typ
• úvodníky MeSH