Relaxing welding residual stresses by diamond like carbon coating on duplex titanium alloys

The distribution of welding residual stresses in titanium alloy plates composed of Ti-6Al-4V (Ti-64) and Ti-4-5Al-3V-2Mo-2Fe (SP700) alloys was measured and calculated under the same heat input. Ti-64 alloy exhibited a higher residual tensile stress than the SP700 alloy due to the low thermal conductivity and thermal dlffusivity of the former alloy, In addition to its high thermal expansion coefficient. Diamond like carbon (DLC) thin film deposited on the as welded titanium alloy plates reduced the magnitude of the welding residual stress caused by the cathodlc arc physical vapour deposition (PVD) process. The distribution of the measured welding residual stresses agreed with the finite element method (FEM) simulated results very well.