Hot cracking is one of the main problems involved in the casting of magnesium alloys and their joining by means of welding. Despite many research done, this type of cracking still constitutes a major problem in industrial practice. The present paper describes the impact of metallurgical, structural and technological factors on the susceptibility of the QE22 alloy to hot cracking of the repaired joints. A technology of repairing the QE22 alloy casts by means of welding and pad welding, was developed. The technology meets the qualification requirements according to EN 15614-4.Keywords: QE22, Cast Magnesium Alloy, Weldability of Magnesium Alloys, Repairing of Magnesium AlloyPękanie gorące jest jednym z głównych problemów odlewania stopów magnezu oraz ich łączenia przez spawanie. Pomimo licznych badań, w praktyce przemysłowej ten rodzaj pękania nadal stanowi istotny problem. W pracy przedstawiono wpływ czynników metalurgicznych, konstrukcyjnych i technologicznych na skłonność stopu QE22 do pękania gorącego złączy naprawczych. Opracowano technologie naprawy odlewów ze stopu QE22 za pomocą spawania i napawania spełniającą warunki kwalifikowania technologii wg EN 15614-4.

The corrosion resistance of the welds made of QE22, ZRE1, and WE43 rare-earth-metals-containing magnesium alloys was investigated in 0.5% NaCl solution saturated with Mg(OH)2 using the electrochemical methods: linear sweep voltammetry, small amplitude cyclic voltammetry, and electrochemical impedance spectroscopy. These tests elucidated how welding influences the susceptibility to corrosion of that class of magnesium alloys. For the sake of comparison AZ91 magnesium alloy was investigated too. All welds were obtained by tungsten inert-gas welding method. In the case of all investigated alloys welds showed corrosion resistance comparable to the base material. However, all rare-earth-metals-containing magnesium alloys show corrosion resistance inferior to AZ91 alloy. Significant differences in corrosion resistance evaluated by different electrochemical methods were observed.

The purpose of the paper was to evaluate the resistance to high temperature corrosion of laser welded joints of finned tubes made of austenitic steel (304,304H) and nickel alloys (Inconel 600, Inconel 625). The scope of the paper covered the performance of corrosion resistance tests in the atmosphere of simulated exhaust gases of the following chemical composition: 0.2% HCl, 0.08% SO 2 , 9.0% O 2 and N 2 in the temperature of 800 o C for 1000 hours. One found out that both tubes made of austenitic steel and those made of nickel alloy displayed good resistance to corrosion and could be applied in the energy industry.

WłaściWości mechaniczne złączy ze stopu magnezu We43W podWyższonej temperaturzeThe wE43 cast magnesium alloy, containing yttrium and rare earth elements, remains stable at temperatures up to 300°C, according to the manufacturer, and therefore it is considered for a possible application in the aerospace and automotive. Usually, it is cast gravitationally into sand moulds and used for large-size castings that find application in the aerospace industry. After the casting process any possible defects that might appear in the casting are repaired with the application of welding techniques. These techniques also find application in renovation of the used cast elements and in the process of joining the cast parts into complex structures. An important factor determining the validity of the application of welding techniques for repairing or joining cast magnesium alloys is the structural stability and the stability of the properties of the joint in operating conditions. In the literature of the subject are information on the properties of the wE43 alloy or an impact of heat treatment on the structure and properties of the alloy, however, there is a lack of information concerning the welded joints produced from this alloy. This paper has been focused on the analysis the microstructure of the welded joints and their mechanical properties at elevated temperatures. To do this, tensile tests at temperatures ranging from 20°C to 300°C were performed. The tests showed, that up to the temperature of 150°C the crack occurred in the base material, whereas above this temperature level the rapture occurred within the weld. The loss of cohesion resulted from the nucleation of voids on grain boundaries and their formation into the main crack. The strength of the joints ranged from 150 MPa to 235 MPa, i.e. around 90 % of strength of the wE43 alloy after heat treatment (T6). Also performed a profilometric examination was to establish the shape of the fracture and to analyze how the temperature affected a contribution of phases in the process of cracking. It was found that the contribution of intermetallic phases in the process of cracking was three times lower for cracks located in the area of the weld.

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