Fracture toughness and fatigue crack growth rate properties of AM repaired Ti–6Al–4V by Direct Energy Deposition

The fracture toughness (KIC) and fatigue crack growth (FCGR) properties of Ti–6Al–4V “repaired” via Direct Energy Deposition (DED) additive manufacturing process were investigated. The KIC and FCGR tests were performed in conformance to the ASTM standard E1820 and E647. Direct current potential drop (DCPD) was used to monitor the crack growth and Digital Image Correlation (DIC) was used to compute the mouth opening displacement. The properties were measured for AM repaired samples along the bond-line present between half AM and half stock Ti–6Al–4V and compared with fully built wrought annealed stock Ti–6Al –4V. The assessment of the crack growth path and the fracture surface were performed using optical and scanning electron microscopy to understand the failure mechanism in detail. The measured properties are discussed in relation to the effects of microstructure. •The fracture toughness (FT) and fatigue crack growth rate (FCGR) of DED repaired Ti-6AL-4V was studied.•The AM repaired coupons show slightly lower value of FT than conventional Ti–6Al–4V.•Fatigue crack growth rates of the AM built were slightly higher than the conventional Ti–6Al–4V.•The study demonstrates the potential of DED repairs to achieve mechanical properties comparable to the conventional Ti–6Al–4V alloy.