Study On Surface Strengthening Technology Of TC4 Welded Joint Based On Residual Stress

The fatigue cracks and even falling blocks still occurred at the welding seam of certain type of engine rotor TC4 titanium alloy blade after vacuum electron beam welding.The problems would affect the quality and reliability of the products.In the paper,the study of the strengthening effect was done in which the composite process of TC4 titanium alloy blade after vacuum electron beam welding with being shot peened and rolled composite process was implemented.The processes of the the vacuum electron beam welding process and composite process strengthening process of titanium alloy were simulated used the finite element analysis method with the the research object of vacuum electron beam welded joint of TC4 and the residual stress taken as the important index and the core criterion to evaluate the fatigue performance of the material.And the residual stresses of TC4 joints of vacuum electron beam welding and of the TC4 joints done by composite process strengthening were measured by X-ray diffraction.By comparing the results of simulation and experimental,and comprehensively analysis of the changes of residual stress of TC4 welded joints after welding and strengthening,the study of changes of fatigue properties of titanium alloy welded joints was done.The simulation results showed that after being shot peened and rolled,the longitudinal residual stress on the surface of TC4 joint decreases obviously.The transverse residual stress in the middle position also decreases sharply from-50 MPa to about-200 MPa.The experimental results showed that after being strengthened by composite process,the transverse residual stress on the surface of TC4 welded joint is reduced from about 35 MPa to about-140 MPa.It was showed the the changing trend of residual stress in TC4 joint was similar by comparing the results of simulation and experimental.And it showed the residual stress on the surface of TC4 welded joint can be decreased by the composite process.The process of being shot peened and rolled compound strengthening can effectively reduce the residual tensile stress on the surface of TC4 welded joint and introduce some residual press stress,so as to effectively improve the fatigue properties of TC4 welded joint.Therefore,the technology of being shot peened and rolled composite strengthening can solve the problems of fatigue cracks or even block loss in the weld of aero-engine titanium alloy blade to a certain extent,and some application prospect in the field of surface integrity manufacturing and anti-fatigue manufacturingof parts can be expected.