Fatigue Behavior and 3D Defect Analysis of 10CrNi3MoV Steel Multi-Pass Welded Joints

Abstract

Multi-pass welded joints of 10CrNi3MoV high-strength low-alloy (HSLA) steel were systematically investigated for high-cycle fatigue (HCF) behavior using microstructural characterization, mechanical behavior, and inherent defect analysis. Gas metal arc welding (GMAW; G1 and G2) and submerged arc welding (SAW; S1 and S2) were performed under two welding conditions each. The welded joints exhibit distinct microstructure and hardness across the fusion zone, coarse-grained heat-affected zone, fine-grained heat-affected zone, and base metal, while maintaining similar tensile strength (684.97 MPa–698.6 MPa). HCF behavior was evaluated at a stress ratio and stress frequency of 0.1 and 120 Hz, respectively. S–N curve was plotted with coefficients of determination values from 0.929 to 0.983. X-ray computed tomography revealed varied internal porosity and inclusions. Paired-case analysis at a maximum stress (σmax) of 168 MPa and 300 MPa demonstrated a strong relationship between defect volume fraction and HCF life. Particularly, the 428-fold increase in porosity volume fraction reduced fatigue life from run-out (>107 cycles) to failure after 773,100 cycles in S1. These findings demonstrate a critical influence of internal weld defects on the HCF life of 10CrNi3MoV welded joints, contributing to improved fatigue-life assessment and providing a basis for future research on fatigue-life assessment.