電子ビーム積層造形したチタン合金Ti6Al4Vの疲労強度向上におけるピーニング法の影響

抄録

Additive manufacturing AM of metallic components is an attractive method for medical implants and aviation components, as it is easy to make porous implants and to reduces weight of the components by nearly free design without consideration of machining. However, fatigue strength of AM metals is relatively weak due to surface roughness and tensile residual stress. Mechanical surface treatment such as shot peening and other shotless peening can improve the fatigue strength of AM metals. In order to demonstrate the improvement of AM metal by mechanical surface treatment, fatigue specimen made of titanium alloy Ti6Al4V manufactured by electron beam melting was treated by shot peening, cavitation peening and laser peening, then tested by a plate bending fatigue test. In the present treatment, recirculating shots accelerated by a water jet was used as shot peening, submerged laser peening with 1,064 nm in wave length was applied as laser peening, and a submerged water jet with 30 MPa of injection pressure was used for cavitation peening. It was concluded that the fatigue strength of the titanium alloy Ti6Al4V manufactured by electron beam melting was improved by 2 times by laser peening, 1.8 times by cavitation peening and 1.7 times by shot peening, comparing with the fatigue strength of as-built specimen, whose fatigue strength was 221 ± 11 MPa.