Understanding Microstructure and Mechanical Properties of Friction Stir Processed Aluminum-Bearing High-Chromium Ferritic Stainless Steel

摘要

Kanthal APMT steel (Fe-22Cr-5Al-3Mo) was developed mainly for using as high temperature furnace elements. This kind of high-Cr ferritic steels is not considered to have good weldability because of a variety of metallurgical issues. Friction stir welding (FSW), a solid state welding process, was applied to a Kanthal APMT 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 examine the feasibility of applying FSW as a joining technique for this steel. Microstructural characteristics were mainly studied by optical microscopy and transmission electron microscopy. The stir zone contained equiaxed grain structure with an average grain size of 13.7 μm. Interestingly, Vickers microhardness profile across the processed zone has revealed no significant change in microhardness.