Failure mode analysis of SMAW welded UNS N08028 (Alloy28) superaustenitic stainless steel under crack growth tests

摘要

The Fatigue Crack Growth (FCG) behavior of welded UNS N08028 (Alloy28) superaustenitic stainless steel was investigated in this paper. Alloy28 superaustenitic stainless steel was welded using Shielded Metal Arc Welding process. The FCG behavior was studied under two load ratios (0.1 and 0.5) and for different specimen configuration: Base Metal (BM), Weld Metal (WM) and Welded Joint (WJ). The results indicated that FCG rates of WM specimen is lower than BM specimen at R = 0.1. Moreover, load ratio affects the FCG rate for BM and WM specimen. In addition, the observation of fatigue crack growth path of WM displayed that crack follows dendritic orientation giving a tortuous crack path, while it is less tortuous for BM specimens. Scanning Electron Microscope (SEM) observations of BM fractured surfaces showed that damage mechanism is intergranular for lower Delta K value, and transgranular for higher Delta K value. Moreover, SEM observations of WM fractured surface showed the presence of welding defects which can affect negatively fatigue crack growth resistance at R = 0.5.