A review of sapphire welding and joining

Aiming at that current research in welding and joining of sapphire mainly focuses on the processing effectiveness,and that the sapphire/metal interface bonding mechanism and reaction dynamics have not been sufficiently investigated,two main concerns of interfacial bonding and thermal stresses are reviewed. Because of sapphire’s chemical inertia,diffusion and reaction between sapphire and weld seam filler materials is very difficult to achieve,which leads to interfacial bonding problems. And because coefficient of thermal expansion of sapphire is relatively low,which can be different from the filler materials,significant thermal stress can be produced in the joints. Three mainstream methods for sapphire welding,i. e. ceramics powder sintering,diffusion bonding and brazing,are reviewed. The reaction mechanism,bonding process and mechanical properties of the sapphire joints are summarized. Noticeable issues and aspects that shall be concerned in the future is proposed. It is expected to provide a valuable reference for the fundamental research and engineering applications in this field.