Corrosion fatigue strength of friction‐welded butt joints in low‐carbon steel

Corrosion behaviour of S25C/S25C friction‐welded butt joints in artificial seawater

“…Previously reported data on the scatter in fatigue life distributions of base material and joint specimens in air and artificial seawater from the perspective of the stress level dependence of the three Weibull parameters, 7 show that the scatter increases with decreasing stress for the base material and joints in air, whereas the scatter decreases with decreasing stress level for the base material and joints in artificial seawater, this trend being more pronounced for the joints and being opposite to that found in air. This feature is attributable to the fact that, for the joints, the fatigue failure nucleation site is limited to the pit base and the scatter in fatigue life distribution decreases in the long-life domain where the corrosion effect is more pronounced.…”

“…The authors have therefore planned a systematic investigation of the fatigue behaviour of friction-welded butt joints in corrosive environments. A previous paper 7 presenting the results obtained in a study of S25C/S25C friction-welded butt joints to JIS specifications has shown that: (1) friction-welded butt joints tested in air have a higher fatigue strength than the base material but have a strength equivalent to that of base materials in the long-life domain when tested in artificial seawater; and (2) the scatter of fatigue life distribution of friction-welded butt joints in artificial seawater decreases with decreasing experimental stress level, which is a trend opposite to that of the base material. Previously reported observations of arrested cracks in the notch root of unfractured specimens and of the occurrence of corrosion pits formed on base material and joint specimens suggest that the sharp reduction in corrosion fatigue strength of joints and the reduced scatter in fatigue life distribution are due to the initiation and growth of corrosion pits preferentially formed on the fibre flow transition planes characteristic of the joints concerned.…”

“…7 Although friction-welded butt joints are widely used and may sometimes be exposed to corrosive environments, the fatigue behaviour of such joints in corrosive environments has so far gone unstudied. The authors have therefore planned a systematic investigation of the fatigue behaviour of friction-welded butt joints in corrosive environments.…”