This paper deals with the possibility of obtaining zinc from waste galvanic sludge, which is formed during galvanic plating. The aim of the experimental and practical part was to obtain zinc after the leaching of galvanic sludge. Leaching was performed in sulfuric acid, nitric acid and hydrochloric acid at different temperatures and time intervals with the addition of oxidizing agents as hydrogen peroxide or ozone. A separation of the leach and filtrate using filtration followed. The leach was further processed by a precipitation of iron and other metals using various agents. After a further filtration, the electrolysis was performed in order to obtain pure zinc on the cathode at the electrical voltage of approximately 3.5 V. Leaching using a solution of sodium hydroxide or potassium hydroxide was also performed when the prior dissolving of a major part of zinc into the leach occurred, while iron and non-ferrous metals remained in the leaching residue. After the filtration of the leach, the electrolysis with a high zinc yield of a purity of more than 99% followed. This way seems to be an optimal one for building a semi-industrial line for galvanic sludge recycling. All the partial products, i.e., the leach, the leaching residue, the filtrate, the solid precipitate and the separated metal on the cathode were subjected to chemical analyses. The analyses results are presented in tables and graphs.

Ni-Al-Mo based alloys can be used as materials for high temperature applications. They can be prepared by various techniques such as an electron beam zone melting, which allows us to obtain the alloys with a directionally solidified structure and unique properties. A plasma-melted Ni-Mo master alloy was used for the preparation of the experimental alloys. Ni-Al-Mo alloys were melted in an induction furnace and then cast centrifugally in the form of bars. These bars were then re-melted in the electron beam zone furnace. The structure of these alloys was multi-phase. The structure was formed by the phases Ni₃(Al,Mo) and (Ni) with variable content of molybdenum. The structure also contained particles rich in molybdenum (Mo, MoNi). The alloys were submitted to the compression tests at a temperature of 800 °C. The yield strength of alloys achieved the value of approx. 800 MPa. The different molybdenum content affected the values of the maximal flow stress. The alloys with higher molybdenum content showed higher maximal flow stress, namely approx. 1300 MPa. The results show that these alloys are very promising for the production of structural components operating at elevated temperatures.

This paper summarizes the results of investigations into heterogeneous P23/P91 welds after long-term creep exposure at temperatures of 500, 550 and 600 °C. Two variants of welds were studied: In Weld A, the filler material corresponded to P91 steel, while in Weld B, the chemical composition of the consumable material matched P23 steel. The creep rupture strength values of Weld A exceeded those of Weld B at all testing temperatures. Most failures in the cross-weld samples occurred in the partially decarburized zones of P23 or WM23 steel. The results of the investigations on the minor phases were in good agreement with kinetic simulations that considered a 0.1 mm fusion zone. Microstructural studies proved that carburization occurred in the P23/P91 weld fusion zones. The partial decarburization of P23 steel or WM23 was accompanied by the dissolution of M₇C₃ and M₂₃C₆ particles, and detailed studies revealed the precipitation of the Fe₂ (W, Mo) Laves phase in decarburized areas. Thermodynamic simulations proved that the appearance of this phase in partially decarburized P23 steel or WM23 is related to a reduction in the carbon content in these areas. According to the results of creep tests, the EBSD investigations revealed a better microstructural stability of the partially decarburized P23 steel in Weld A.