|Spoluautoři VODÁREK Vlastimil|
The paper deals with results of studies on the minor phase evolution in wrought niobium-bearing AISI 316LN steels during creep exposure at 600 °C. Casts B and C contained 0.1 and 0.3 wt.%Nb, respectively. Creep rupture tests with a constant tensile load were carried out in air with time to rupture up to ca 220,000 hours. The growing niobium content reduced the minimum creep rate and prolonged the time to the onset of the tertiary stage of creep. Detailed microstructural studies were conducted in order to understand the factors and processes responsible for the observed differences in creep behaviour. Investigations were carried out by means of optical metallography, transmission and scanning electron microscopy. After long-term creep exposure the following minor phases were identified in the casts investigated: primary Z-phase (particles not dissolved during solution annealing), secondary Z-phase, Laves phase, M6X and -phase. The attention has been paid to evaluation of thermodynamic and kinetic stability of minor phases during long-term creep exposure.