One of important resistance parameters introduced into engineering calculations for selection of materials and evaluation of their operating properties is material crack resistance. Contrary to the stationary fracture toughness K1c, J," the dynamic fracture toughness K,d, J,d, ~ is also an important parameter. In this paper, the authors have evaluated the relation between the parameters of the dynamical fractures toughness and the structure as well as impact resistance in chosen frictionally welded joints. The above-mentioned joints are made of the following steel parts: N9E-45, 18G2A-St3S, St3S-45, 40H-45, 18G2A-40H. In this experiment, the instrumented bending impact test was used.

The article provides results of the microstructure examinations and mechanical properties (hardness and microhardness tests) of the welded joint T91 steel taken from the live steam pipeline. Examined joint has been exploited for about 45 000 hours in a temperature of 535oC and the steam pressure equals to 13.5 MPa. Examined joint was made as a double bead by the additional materials with a different chemical composition. It was proved that the joint was characterized by a differential microstructure on the cross-section of the weld. Moreover, decarburized zone in the lower alloyed material and carbides zone in the higher alloyed material were revealed in the weld line and on the boundary penetration of beads. Furthermore, it was shown that the main mechanism of a joint degradation is a privileged precipitation of carbides on the grain boundaries, and an increase of their size.

Research was conducted on welded joints of martensitic steel Thor 115 made with two filler materials – CrMo91 and Ni 6082. The scope of the investigations included: non-destructive and destructive testing. The macro- and microstructural investigations revealed correct structure of the weld, without welding imperfections. In the joint welded with Ni 6082, the so-called Nernst’s layers and δ-ferrite grains were visible. The investigations of the analysed joints showed that their properties, i.e. tensile strength and impact strength, were higher than the required minimum, whereas hardness was lower than the maximum value of 350 HV permitted for this group.

The development of power industry obligates designers, materials engineers to create and implement new, advanced materials, in which Inconel 617 alloy is included. Nowadays, there are a lot of projects which describe microstructure and properties of Inconel 617 alloy. However, the welded joints from mentioned material is not yet fully discussed in the literature. The description of welded joints microstructure is a main knowledge source for designers, constructors and welding engineers in estimating durability process and degradation assessment for elements and devices with welds of Inconel 617 alloy. This paper presents the analysis and assessment of advanced nickel alloy welded joints, which have been done by tungsten inert gas (TIG). Investigations have included analysis made by light microscope and scanning electron microscope. The disclosed precipitates were identified with Energy Dispersive Spectroscopy (EDS) microanalysis, then it were done X-Ray Diffraction (XRD) phases analysis. To confirm the obtained results, a scanning-transmission electron microscope (STEM) analysis was also performed.

The purpose of the article was to create a comprehensive procedure for revealing the Inconel 617 alloy structure. The methodology presented in this article will be in future a great help for constructors, material specialists and welding engineers in assessing the structure and durability of the Inconel 617 alloy.