Recent Development in Brazing Titanium and Titanium/Steel Joints Using Filler Metal Deposited by PVD Technique

Microstructure aspects and bonding characteristics of the vacuum brazed Ti/Ti and Ti/steel were investigated. Thin-copper films, with different thicknesses, were deposited on the brazed metals by physical vapor deposition (PVD) technique to serve as brazing filler metal. Test joints were processed at a temperature of 910^oC and 960^oC. Meanwhile, the used holding times at brazing temperature were 15, 30, and 90 min. The microstructure of joints was studied by means of Optical Microscopy, Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX), and X-ray Diffraction (XRD). Additionally, the joints were characterized in order to determine the brittle intermetallic compound (IMC) in the interfacial layer and the shear strength of the joints was evaluated. Our experimental results showed that sound joints with good wetting quality, lack of pores and cracks can be achieved. Intermetallic phases such as Ti2Cu, TiCu, FeTi, and Fe2Ti were predicted from the chemical analyses and XRD technique. The Ti/Ti joints achieved higher shear strength than Ti/steel joints and there is a tendency for the shear strength to increase when the Cu-deposited layer completely disappeared by diffusion process. Fracture of joints took place mainly at Ti2Cu phase in case of Ti/steel joints. On the other hand, Ti/Ti joints showed always a fracture path at TiCu phase.