The most frequent failure causes in super ferritic stainless steels: are they really super?

Ferritic stainless steels (FSSs) are classified according to their "generation", where the 4th generation was commercially branded as super fern tic stainless steels (SFSSs). SFSSs contain C content below 0.02% C, Cr above 25%, Ni and Mo between 2 and 4% and eventual additions of Nb or Ti. The combination of good mechanical properties and top corrosion resistance makes the SFSSs candidates for applications in chemical, petrochemical and desalination plants. However, SFSS components might be subjected to mechanical embrittlement and environmentally induced failures, especially when these components are exposed to temperatures above 300 degrees C, which promotes the precipitation of stable and deleterious phases, such as sigma, chi and Laves phases, and a' clusters. The main properties of the SFSSs will be compared other generations of FSSs to provide a broader outlook of the boundary conditions for their selection. Finally, the main phase transformations of the SFSSs will be concisely presented along with their typical microstructures, microfractographies and crack propagation paths in order to depict the role of these stable and deleterious phases on the processing and service life of SFSS components. (C) 2019 The Authors. Published by Elsevier B.V.