Theses and Dissertations Collection

Commercial Kanthal APMTTM steel (Fe-22Cr-5Al-3Mo) was developed for use as high-temperature furnace elements. The alloy is not considered to have good weldability because of various metallurgical issues. Friction stir welding (FSW) was applied to a Kanthal APMTTM plate in a bead-on-plate configuration using a PCBN tool with a tool rotation rate of 600 RPM and a traverse speed of 25.4 mm/min. Microstructure and mechanical properties were evaluated to determine the weld quality and to examine the feasibility of applying FSW as a joining/processing technique. Microstructural characteristics were mainly studied both by optical and electron microscopy. The stir zone contains small equiaxed grain structure. Interestingly, Vickers microhardness profile across the processed zone has revealed no significant change in microhardness. Thermal stability of the alloy at 475 oC is also studied. The results show that FSW slows down the embrittlement effect but does not entirely stop it.