ABSTRACT
The problem of creep resistance is considered in the temperature range 470 to above 2200 K; the lower limit is fixed by plastics, the upper by tungsten filaments. The most frequently met temperatures in industrial applications are below about 1500 K. Considering material properties that determine its applicability, the melting point is undoubtedly crucial. This property favors ceramics and refractory metals. Unfor tunately, such materials are brittle and become ductile only at temperatures slightly below the melting point. The next criterion is the dependence of normalized yield stress (Oy IE) on homologous temperature (TITM). This dependence is shown in Fig. 3.1. As seen, the best properties possess solids with a covalent bond. In pure metals, the creep activation energy strictly correlates with the self-diffusion activation energy (see Fig. 3.2). It is seen that metals fall into five groups. The structure effect should be noted; austenitic steels behave better. Figure 3.3 shows the maximum working temperatures of creep-resisting alloys for the case where the only signifi cant factor is creep.
