In the paper, verification of welding process parameters of overlap joints of aluminium alloys EN AW-6082 and EN AW-7075, determined on the grounds of a numerical FEM model and a mathematical model, is presented. A model was prepared in order to determine the range of process parameters, for that the risk of hot crack occurrence during welding the material with limited weldability (EN AW-7075) would be minimum and the joints will meet the quality criteria. Results of metallographic and mechanical examinations of overlap welded joints are presented. Indicated are different destruction mechanisms of overlap and butt joints, as well as significant differences in their tensile strength: 110 to 135 MPa for overlap joints and 258 MPa on average for butt joints.

The paper presents results of the possibility of adapting the Althoff-Radtke test for High Chromium Cast Iron. The Althoff-Radtke test is a

clump attempt used for steel. The Althoff-Radtke test has four different lengths of clamp which qualifies it as a test to quantitatively take

into account different kinds of shrinkage ΔL. The length of the slot of the cracked corner and the length of each staple (50 - 350 mm) are

the parameters tendency to cast cracks. Castings of white cast iron have a high tendency to hot cracking due to the large range of

solidification temperatures, unfavorable kinetics parameters of shrinkage, and especially a lack of expansion before shrinkage. Shrinkage

of high chromium white cast iron is similar to the shrinkage of cast steel, and is approximately 2%. Therefore it is important to test

susceptibility to hot cracks. Research was carried out under industrial conditions. Four melts were performed, one of the initial chemical

composition and the other three modified by different amounts of Fe-Ti, respectively, 0.25%, 0.5% and 0.75% Fe-Ti. The propensity for

hot cracking was based on the observation of the dark surface in the corner of the sample. The study shows that the Althoff-Radtke test can

be adapted to determine the tendency for hot cracking of high chromium cast iron. It should however be noted that the test results cannot be

compared with those for other alloys.

Nickel alloys, despite their good strength properties at high temperature, are characterized by limited weldability due to their susceptibility to hot cracking. So far, theories describing the causes of hot cracking have focused on the presence of impurities in the form of sulphur and phosphorus. These elements form low-melting eutectic mixtures that cause discontinuities, most frequently along solid solution grain boundaries, under the influence of welding deformations. Progress in metallurgy has effectively reduced the presence of sulphur and phosphorus compounds in the material, however, the phenomenon of hot cracking continues to be the main problem during the welding of nickel-based alloys. It was determined that nickel-based alloys, including Inconel 617, show a tendency towards hot cracking within the high-temperature brittleness range (HTBR). There is no information on any structural changes occurring in the HTBR. Moreover, the literature indicates no correlations between material-related factors connected with structural changes and the amount of energy delivered into the material during welding.

This article presents identification of correlations between these factors contributes to the exploration of the mechanism of hot cracking in solid-solution strengthened alloys with an addition of cobalt (e.g. Inconel 617). The article was ended with development of hot cracking model for Ni-Cr-Mo-Co alloys.