Phase high-temperature alloys

Popov A.A., Drozdova N.A. (1997) Principles of alloying of two-phase high-temperature alloys based on Ti.-FizikaMetallovMetallov., 84,123-131. (In Russian)... 

Corrosion Resistance of Nickel-based Alloys. Nickel-based alloys are solid solutions based on nickel. Nickel-based alloys used for low-temperature aqueous or condensed systems are generally known as corrosion-resistant alloys (CRA), and nickel alloys used for high-temperature applications are known as heat-resistant alloys (HRA), high-temperature alloys (HTA), or superalloys. The corrosion performance could change due to the presence of second phase or a weld seam. (Rebak)5... 

NiAl can be alloyed with further elements in order to form ternary phases with a B2 structure which is then known as an L2o structure, too, or to obtain additional phases in equilibrium with NiAl. Fe, as well as Co, can substitute for Ni in NiAl completely without affecting the B2 structure, as is expected in view of the binary B2 phases FeAl and CoAl. Correspondingly, the ternary Ni-Fe-Al phase diagram, which is of importance with respect to conventional high temperature alloys, shows the extended B2 phase field and the respective equilibria with NijAl and Al-rich phases on the one hand and with disordered b.c.c. Fe and f.c.c. Fe on the other (Bradley and Taylor, 1938 Dannohl, 1942 Bradley, 1951 Hao et al., 1984). The Ni-Al-Co system behaves in an analogous way (Hao et al., 1984 Ishida et al., 1991 a, 1993). Other ternary systems have been re-... 

Corrosion Resistance of Nickel-Based Alloys There are three types of nickel-based alloys (i) CRA (ii) heat-resistant alloys and (hi) high-temperature alloys or super alloys. The corrosion performance can change because of the presence of a weld seam as a second phase. 

Heat treatment. Solid-solution-strengthened high-temperature alloys are normally supplied in the solution-heat-treated condition unless otherwise specified. In this condition, microstructures generally consist of primary carbides dispersed in a single-phase matrix, with essentially clean grain boundaries. This is usually the optimum condition for the best elevated temperature properties in service and the... 

Al and Cr are commonly required for high-temperature alloys since they can form stable and slow-growing oxide scales, AI2O3 and Cr203. In these composites, Al and Cr could improve the oxidation resistance of Nb solid solutions (Nbss) and silicide [286]. Cr can also stabilise the Cr-rich Laves phase. It was believed that introduction of this phase could enhance the oxidation resistance of the composites [289,291]. However, at low to moderate temperatures, e.g. 800°C, higher oxidation rates and lower adherence of oxide scales were observed with increase of the Cr concentration in the Al-containing Nb-Ti-Si composites [298]. 

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