Research Projects

Third generation advanced high strength steel (AHSS) based on bainitic microstructure has progressively gained attention because of their excellent combination of strength and toughness. In many occasions, high-strength bainitic steels have shown strength comparable to martensite and ductility comparable to ferrite. These steels, consisting of sub-unit of bainitic ferrite and films of retained austenite have emerged as a potential candidate to replace the conventional pearlitic steel for heavy-haul railway track applications. However, large scale implementation of bainitic steel in such applications not only depends on the strength and ductility; other aspects, for example weldability and hydrogen embrittlement are vital as well. Majority of the weld joint cracks develop from the heat affected zone (HAZ) during post-weld cooling, because of residual stress generated from martensitic transformation due to higher cooling rates. Proper selection of welding process and related process parameters are therefore extremely importance to avoid any such incidents. Furthermore, high-strength steels are more susceptible to hydrogen embrittlement. The bainitic steel however consists of an alternative arrangement of bainitic ferrite (BCC) and retained austenite (FCC). Since the diffusivity of hydrogen in austenite is relatively sluggish, its presence can alter the mechanisms of hydrogen embrittlement in the steel. A clear correlation between the microstructure, extent of hydrogen entrapment and prevailing damage mechanisms in such steels is therefore needed in order to explore the full potential of high-strength bainitic steels.