High-cycle tensile-tensile fatigue performance of niobium alloy: Conventional vs wire-arc additive manufacturing

This study explores the high-cycle fatigue (HCF) behavior of a niobium alloy, NbZr1, fabricated using wire-arc additive manufacturing (WAAM), and compares its fatigue strength to that of its powder metallurgy (PM)-produced counterpart. The analysis was conducted at three different stress levels, each characterized by a non-zero mean stress and a stress ratio of 0.1. The fatigue life under tensile-tensile fatigue loading ranged from 10 4 to 10 8 cycles for all tested samples. WAAM-produced NbZr1 exhibited a shorter average fatigue life compared to PM-NbZr1. Examination of the fracture surfaces revealed consistent fracture morphology across all loading conditions in PM-NbZr1 samples, whereas WAAM-NbZr1 samples showed varied fracture behavior. Notably, the crack propagation regions in WAAM-NbZr1 exhibited contrasting behaviors under different loading conditions. While PM-NbZr1 demonstrated typical ductile failure with elongated dimples near the final fracture region, WAAM-NbZr1 showed more pronounced cleavage crack growth, accompanied by void nucleation and coalescence along the ZrO 2 particles during fatigue crack propagation. The interdendritic regions containing fine ZrO 2 particles were identified as a key factor influencing crack propagation and final fracture location in WAAM-NbZr1.