Dissimilar girth joints under combined cyclic thermal and mechanical loading - experimental and numerical investigations

Experimental and numerical investigations were conducted to quality dissimilar girth welds in tubes fabricated in 9% Chromium steels T91 and E911 and the austenitic steel X3 CrNiMoN 17-13 for service temperatures up to 625°C. Girth welds were produced on tubes by different welding processes such as automatic and manual TIG welding as well as friction welding. Ni-based consumables were used in the arc welding processes and NiCr15Fe transition rings in case of friction welded joints. The girth welds were investigated in the annealed as well as in the quenched and tempered post weld condition. The tubes were tested under combined cyclic thermal and mechanical loading. A full material characterization (tensile tests at different strain rates, creep tests, low cycle fatigue tests at temperatures up to 650°C for base metals and weld metals as well as weld thermal simulated heat affected zones were performed.