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.