Transitional behavior of fatigue crack growth in welded joint of 25Cr2Ni2MoV steel

Transitional behavior of fatigue crack growth is observed for initial notches located at base metal, weld metal and heat-affected zone of 25Cr2Ni2MoV steel welded joint. Results indicate that both microstructures and load ratio R contribute to the transition. Greater roughness at both weld metal and base metal indicates a more pronounced roughness-induced crack closure in the near-threshold regime than that at heat-affected zone, especially at lower R. This transition is dominated by both Delta K and K-max which depends on R. An estimation of Delta K at transition point is proposed, which agrees fairly well with the experimental data. (C) 2015 Elsevier Ltd. All rights reserved.