Abstract
The effect of Laves phase precipitation on the fatigue strength in type 429EX niobium-contained ferritic stainless steel was investigated. When this material is exposed to the temperature range of 700-900°C, the precipitation of the Laves phase (Fe2Nb) occurs. Fully reversed axial loading fatigue tests have been conducted in laboratory air using type 429EX aged at 700, 800 or 900°C for 100h. The fatigue strengths of the specimens aged at 700°C were nearly the same as that of un-aged ones due to the fine Laves phase precipitation in a-phase. Whereas the aging at 800°C and at 900°C decreased fatigue strengths, which could be attributed to the coarsening of grains and precipitated Laves phases along the grain boundaries.
