Residual stresses and fatigue crack growth in friction surfacing coated Ti-6Al-4V sheets

Abstract

The relation between the translational stud speed and the residual stress (RS) state of Friction Surfacing (FS) coated 2 mm thick Ti-6Al-4V sheets was studied using synchrotron diffraction. The influence of the RS state on fatigue crack propagation (FCP) was studied using C(T)-100 samples. It was shown that an active zone of tensile RS is present in the coated region, inducing compressive stresses in the remaining sheet. Higher depositing stud translational speeds show a tendency towards high RS peak values. The deposited material thickness has an influence on the RS distribution. FCP tests have shown branching cracks deflecting away from the coating, possibly due to the compressive RS around it. Cracks have propagated significantly slower than in uncoated samples. RS measurements on cracked samples have revealed tensile RS peaks at the crack tips with high values of 350 MPa in the direction parallel to the intended crack propagation, which prevent the cracks from reaching the coated region.