Vliv přísady niobu na creepové chování oceli typu AISI 316LN

Abstract

This diploma thesis deals with heat-resistant austenitic steels, AISI 300 series, their creep behaviour and microstructural stability during creep exposure. In this diploma thesis the effect of stabilization elements, especially of niobium or titanium, on the stability of minor phases at high temperatures was discussed. In the experimental part of this thesis the TEM analysis of microstructure in a specimen of a niobium-bearing AISI 316LN steel after long-term creep exposure was made. The chemical composition of individual phases was determined by the EDS. The degradation effects of creep exposure on minor phases were investigated. The positive effect of niobium on the Z-phase stability was proved. However, the niobium also accelerated the precipitation of intermetallic phases (sigma-phase, éta-Laves).