Environment-Assisted Fatigue Crack Propagation (EAFCP) Behavior of Ti64 Alloy Fabricated by Direct Energy Deposition (DED) Process

Environment-assisted fatigue crack propagation (EAFCP) behavior of as-built and β-annealed Ti64 specimens manufactured by direct energy deposition (DED) process was examined in air and 3.5 pct NaCl solution under an anodic applied potential of E corr + 0.05 V SCE . As-built DED Ti64 specimen was found to be susceptible to EAFCP in 3.5 pct NaCl solution, and β anneal did not decrease the sensitivity to EAFCP. It was suggested that Cl − bearing environment tended to decrease the tendency for crack bifurcation during EAFCP of DED Ti64 specimen, because of local corrosion damage at boundaries between α and β phases. Since crack bifurcation increases the resistance to fatigue crack propagation (FCP) by reducing effective ∆ K (stress intensity factor range) at the tip of crack, the FCP rates of DED Ti64 specimen increased in 3.5 pct NaCl solution.