The effect of pit size and density on the fatigue behaviour of a pre‐corroded martensitic stainless steel

Abstract

UNS S17400 steel is used in turbines for the aerospace and utility industries. While it is generally corrosion resistant, it is susceptible to pitting when exposed to aqueous chloride environments. Effects of pitting characteristics, such as depth, width, and local density on fatigue life, have been studied in this work to better inform criteria for component replacement or repair. While pit depth correlates well with cracking, the deepest pit never initiated the crack that ultimately led to failure. The clustering of pits, or local pitting density, also correlated well with crack initiation location; however, the densest region of pitting was not always the location where cracking occurred. There is likely no single metric that directly correlates pitting with fatigue cracking, rather there is a combination of pitting characteristics that ultimately lead to cracking. The results from this work suggest that pit depth and local pitting density are among the more important metrics.

The influence of corrosion pit–pit spacing on the pit‐to‐crack transition and fatigue lifetime

“…Dominguez et al 39 investigated the effects of dimension and proximity of two artificial defects obtained by drilling holes on the fatigue endurance and reported that when the two defects approach, a reduction in the fatigue life is observed. McMurtrey et al 40 investigated the effect of clustering of pits on the fatigue behavior of stainless steel and reported that local pitting density correlated well with crack initiation location. In a study by Songbo et al, 41 the interactions between double critical pits were found to facilitate a faster accumulation of local plastic strains, thus leading to prematurely initiated ductile cracks.…”

Effect of corrosion on the fatigue behaviour of butt welds of G20Mn5QT cast steel and Q345D hot rolled steel in 3.5‐wt% NaCl solution

“…According to fracture analyses, pitting corrosion occurs on the surface of welded metallic materials during corrosion fatigue, which is one of the reasons leading to the nucleation of fatigue cracks 19,20 . McMurtrey et al 21 studied the effect of the pit size and density on the fatigue behaviour of precorroded martensitic stainless steel (UNS S17400 steel). It was found that precorrosion leads to pitting corrosion on the surface of the material, and the pit depth correlates and high local pit density are strongly correlated with the crack formation location.…”

Quantitative Characterization of the Spatial Distribution of Corrosion Pits Based on Nearest Neighbor Analysis

“…However, in most practical cases, the procedure is not necessarily governed by the initiation and growth of a single pit or crack. Typically, the corrosion-fatigue mechanism involves the appearance of multiple pits, mainly at inclusion sites where they serve as local galvanic cells, followed by the pit-growth stage [4][5][6][7][8][9]. Afterwards, a multiplicity of small fatigue-cracks originates from the pits as stress-concentrators, the interaction and resultant coalescence of which eventually lead to the formation of a significant crack that will dominate fracture [10], [11].…”