Best way to join cast titanium components
Laser welding in an argon gas atmosphere is a method of choice for joining titanium components of dental prostheses, because the coherent, high-intensity laser pulse of light can be focused in a small region and melt the substrate without extensive microstructural damage to the surrounding areas. An advantage of welding is that the joint will be composed of the same pure titanium as the substrate components, thereby preserving the excellent biocompatibility potential of CP Ti. 
Phillip’s 12th edition page 392
Laser Welding
Oven Soldering
Torch Soldering
Infrared Soldering