Superalloys show a good combination of mechanical strength and resistance to surface degradation under the influence of chemically

active environments at high temperature. They are characterized by very high heat and creep resistance. Their main application is in gas

turbines, chemical industry, and in all those cases where resistance to creep and the aggressive corrosion environment is required. Modern

jet engines could never come into use if not for progress in the development of superalloys. Superalloys are based on iron, nickel and

cobalt. The most common and the most interesting group includes superalloys based on nickel. They carry loads at temperatures well in

excess of the eighty percent of the melting point. This group includes the H282 alloy, whose nominal chemical composition is as follows

(wt%): Ni - base, Fe - max. 1.5%, Al - 1.5% Ti - 2.1%, C - 0.06% Co - 10% Cr - 20% Mo - 8.5%. This study shows the results of thermal

analysis of the H282 alloy performed on a cast step block with different wall thickness. Using the results of measurements, changes in the

temperature of H282 alloy during its solidification were determined, and the relationship dT / dt = f (t) was derived. The results of the

measurements taken at different points in the cast step block allowed identifying a number of thermal characteristics of the investigated

alloy and linking the size of the dendrites formed in a metal matrix (DAS) with the thermal effect of solidification. It was found that the

time of solidification prolonged from less than ome minute at 10 mm wall thickness to over seven minutes at the wall thickness of 44 mm

doubled the value of DAS.

Nickel alloys belong to the group of most resistant materials when used under the extreme operating conditions, including chemically

aggressive environment, high temperature, and high loads applied over a long period of time. Although in the global technology market

one can find several standard cast nickel alloys, the vast majority of components operating in machines and equipment are made from

alloys processed by the costly metalworking operations. Analysis of the available literature and own studies have shown that the use of

casting technology in the manufacture of components from nickel alloys poses a lot of difficulty. This is due to the adverse technological

properties of these alloys, like poor fluidity, high casting shrinkage, and above all, high reactivity of liquid metal with the atmospheric air

over the bath and with the ceramic material of both the crucible and foundry mold. The scale of these problems increases with the expected

growth of performance properties which these alloys should offer to the user.

This article presents the results of studies of physico-chemical interactions that occur between theH282alloy melt and selected refractory

ceramic materials commonly used in foundry. Own methodology for conducting micro-melts on a laboratory scale was elaborated and

discussed. The results obtained have revealed that the alumina-based ceramics exhibits greater reactivity in contact with the H282 alloy

melt than the materials based on zirconium compounds. In the conducted experiments, the ceramic materials based on zirconium silicate

have proved to be a much better choice than the zirconia-silica mixture. Regardless of the type of the ceramic materials used, the time and

temperature of their contact with the nickel alloy melt should always be limited to an absolutely necessary minimum required by the

technological regime.

Inconel 713C alloy belongs to the group of materials with high application potential in the aerospace industry. This nickel alloy has excellent features such as high strength, good surface stability, high creep and corrosion resistance. The paper presents the results of metallographic examinations of a base material and padding welds made by laser beam on the Inconel 713C alloy. The tests were made on precisely cast test plates imitating low - pressure turbine blades dedicated for the aerospace industry. Observations of the macro- and microstructure of the padding welds, heat-affected zone and base material indicate, that the Inconel 713C alloy should be classified as a hard-to-weld material. In the investigated joint, cracking of the material is disclosed mainly in the heat-affected zone and at the melted zone interface, where pad weld crystals formed on partially melted grains. The results show that phases rich with chromium and molybdenum were formed by high temperature during welding process, which was confirmed by EDS analysis of chemical composition.

The results of castability and structures researches of two nickel base alloys - Ceranium CN and Magnum AN applied on casting of the crowns and dental bridges are presented. Studies were carried out on the alloys cast under the centrifugal force to the moulds made by the lost wax method using production line of ROKO. Having regard to a specific technology of casting and possibility of ROKO production line, to the estimation of alloys castability a spiral test was adjusted with a 0,8 mm and a 2,5 mm diameter of test casting. Measuriements executed on a 20 test castings allowed to establish, that castability of Magnum AN alloy was 65 % greater than castability of Ceranium NC alloy. The results of thermodynamics calculations of the equilibrium and nonequilibrium crystallization (Scheil model) of the investigated alloys are presented too. The characteristic temperatures of phase transformation and forecast phase composition of alloys for both kind of crystallization were calculated. It is established after structural supervisions, that the investigated alloys crystallize in dendryte form and in centrifugal casting conditions have cooling rate sensivity and inclination to texture structure forming in outmost layer of casting. Phase composition of alloys corresponds to the results of thermodynamics calculations of the nonequilibrium crystallization conditions.

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.

As a result of experimental data processing, the ratio of alloying elements Кγ' was proposed for the first time, which can be used to assess the mechanical properties, taking into account the complex effect of the main alloy components. The regularities of the influence of the composition on the properties of heat-resistant nickel alloys of equiaxial crystallization are established. It is shown that for multicomponent nickel systems it is possible with a high probability to predict a mismatch, which significantly affects the strength characteristics of alloys of this class. A promising and effective direction in solving the problem of predicting the main characteristics of heat-resistant materials based on nickel is shown.

A deep eutectic solvent, ethaline (as a typical representative of new-generation room temperature ionic liquids), was used to anodically treat the surface of copper-nickel alloy (55 wt.% Cu). Anodic treatment in ethaline allows flexibly affecting the patterns of surface morphology: formation of stellated crystallites and surface smoothing (i.e. electropolishing) are observed depending on the applied electrode potential. The measured values of roughness coefficient ( R_a ) well correlate with the changes in surface morphology. Anodic treatment of Cu-Ni alloy in ethaline contributes to a considerable increase in the electrocatalytic activity towards the hydrogen evolution reaction in an alkaline aqueous medium, which can be used to develop new high-efficient and inexpensive electrocatalysts within the framework of the concept of carbon-free hydrogen economy.