抄録
Friction welded butt joints are widely used as machine members and structural elements, but valid evaluation method of the joint performance, especially under service load conditions, has not been established yet. Evaluation of corrosion fatigue behaviors of the joint is one of the important problem, for some joints are used in pollutive environments. In our previous paper, corrosion fatigue behaviors in artificial seawater were investigated on S25C/S25C friction welded butt joints. The results indicated that the S-N curve for corroision fatigue strength of the joint specimen showed steeper slope than that of the base material and the strength of the joint took almost the same value as that of the base material specimen in long life region, and the scatter of fatigue lives became smaller in accordance with the increase in fatigue life contrary to the case of the base material specimen. Detailed observations of corrosion pits and non-propagation cracks of run-out specimens suggested that the above mentioned corrosion fatigue characteristics of the joint was governed by corrosion pits generated preferably on exposure surface of the transitional plane of fiber flow directions developed at the final stage of friction welding process.
The present study was carried out to clarify the corrosion behaviors of the joint in more detail. Joint specimens were immersed in artificial seawater at stress free condition during 5 and 10 days. Distribution of corrosion pits near the weld interface and geometrical factors of pits were evaluated precisely, and the difference of corrosion behaviors between the joint and the base material were also discussed. The results of this study gives valid support for the estimation on the corrosion fatigue characteristics of the joint indicated in our previous paper.
