Effect of short-term compressive overloads on the crack resistance of the metal of housing parts of steam turbines under conditions of creep

Abstract

1. The effect of periodic compressive overloads on crack resistance under conditions of creep is ambiguous and depends on the structure of the material, the periodicity of load application, and apparently also on the temperature. 2. There exist conditions when periodic compressive overloads may have a substantial deleterious effect on the long-term strength of the metal of turbine housing parts of steels 15Kh1M1FL and KhN35VT in operation with a “prepared” crack. 3. Reduction of the time between overloads impairs the crack resistance of metal. This need not be taken into account if the time between overloads exceeds a certain value for each kind of steel: 150 h for steel 15Kh1M1FL at 565°C, and 2400 h for steel KhN35VT at 650°C.