Experimental study on high-cycle fatigue behaviour of butt welds made of corroded AISI 304 stainless steel and Q460 high-strength steel

The weld is normally susceptible to both corrosion and fatigue in a corrosive environment, which may lead to the development of fatigue cracks and even the destruction of entire structures. The durability and strength of structures could be severely challenged, especially for those offshore structures in a harsh corrosive environment. However, no experimental work has been undertaken to investigate the high-cycle fatigue behaviour of butt welds made of corroded AISI 304 stainless steel and Q460 high-strength steel. Hence, this study reports the details of an experimental investigation into the corrosion properties and the high-cycle fatigue behaviour of corroded AISI 304 stainless steel and Q460 high-strength steel with transverse and longitudinal butt welds. Alternate immersion tests, tensile tests and high-cycle fatigue tests were conducted on 56 specimens. In the tensile test, the comparison and analysis on the change and degradation of the welded joint's mechanical properties before and after corrosion were carried out. In the fatigue test, the relationship between the stress range and fatigue life of the specimens was obtained using double-log function model. The influence of corrosion on the fatigue behaviour of welded joints was studied through fracture morphology analysis. The results indicated that after 168 days’ corrosion, the mass loss rate of AISI 304 steel welded joints was around 0.0394% and that of Q460 high-strength steel ones was higher than 19.29%, and for both materials, the fatigue life was decreased by more than 49.57% for transverse welded joints and 75.56% for longitudinal welded joints under high-cycle fatigue loading. Finally, a comparison between test fatigue life and design values obtained from European Code (EN 1993–1-9), Australian Standard (AS 1210–2010), British Standard (BS 7608) and Det Norske Veritas (DNV) was established, indicating that the existing design standards cannot accurately predict the fatigue life of such corroded butt welds made of these two materials. It is recommended that design standards should refine the classification system and introduce environmental parameters for improvement.