Improvement in cavitation erosion resistance of AISI 316L stainless steel by friction stir processing

• Published in: Applied surface science Vol. 308; pp. 184 - 192
• Main Authors: Hajian, M., Abdollah-zadeh, A., Rezaei-Nejad, S.S., Assadi, H., Hadavi, S.M.M., Chung, K., Shokouhimehr, M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30.07.2014; Elsevier
• Subjects: Austenitic stainless steel; Cavitation erosion; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Damage mechanism; Exact sciences and technology; Friction stir processing; Grain size; Physics; Grain size; Austenitic stainless steel; Friction stir processing; Cavitation erosion; Damage mechanism; Friction; Damage; Cavitation; Stainless steels; Erosion
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2014.04.132

•Friction stir processing (FSP) was used to refine the surface microstructure of 316L austenitic stainless steels.•The finer the grains, the higher cavitation erosion resistance was observed.•The development of a favorable crystallographic orientation and remarkable reduction of twin boundaries at the stir zone contribute to the promotion of cavitation erosion resistance in the FSP samples.•The cavitation erosion damage is controlled by a group of mechanisms comprising grain boundary destruction, microcracking and fatigue crack propagation. Commercial AISI 316L plates with the initial grain size of 14.8μm were friction stir processed (FSP) with different processing parameters, resulting in two fine-grained microstructures with the grain sizes of 4.6 and 1.7μm. The cavitation erosion behavior, before and after FSP, was evaluated in terms of incubation time, cumulative mass loss and mean depth of erosion. A separate cavitation erosion test was performed on the transverse cross section of a FSP sample to reveal the effect of grain structure. It was observed that FSP samples, depending on their grain size, are at least 3–6 times more resistant than the base material against cavitation erosion. The improvement in cavitation erosion resistance is attributed to smaller grain structure, lower fraction of twin boundaries, and favorable crystallographic orientation of grains in FSP samples. The finer the grain size, the more cavitation erosion resistance was achieved. Moreover, the microstructures of eroded surfaces were studied using a scanning electron microscope equipped with EBSD, and an atomic force microscope. The mechanisms controlling the cavitation erosion damage in friction stir processed AISI 316L are also discussed.