Study On Vacuum Diffusion Bonding Of Zircaloy-4 And 316L Stainless Steel

Zirconium is a rare and expensive nonferrous metal. Because of low absorption cross-section for thermal neutrons and good consistent with nuclear fuel , zircaloy has been widely used as cladding material for fuel elements and in-core structural components in water-cooling reactor. The bonding of zircaloy and stainless steel is an important technology in project of nuclear reactor and it has not been solved completely as yet. Two main difficulties are encounterd in bonding of zircaloy and stainless steel. The first difficulty is the formation of brittle intermetallic compounds which reduce the mechanical strength and corrosion resistance of the joint. The second is the large mismatch in thermal expansion coefficient of the two materials which lead to large residual stresses in bonding region. Better results have been obtained by vacuum diffusion bonding for the different kinds of materials. Researching the vacuum diffusion bonding of zircaloy and stainless steel plays an important role in theory and practice, especially studying the relationship among diffusion bonding parameters, component, structure and performance.By the mechanical testing, the characteristics of metallographical observation, X-ray diffusion analyses and energy dispersive X-ray analyses on the joints under various experimental conditions, the relationship of the diffusion bonding parameters and the joint strength were drawn.The following conclusions are obtained in this paper:1 There was a distinctly rule between the quantity continuity and homodispersivity of the avulsed structure in the section of zircaloy and shear strength of the joints.2 Shear strength of the joints increase as the increase of quantity of Ag diffusing into zircaloy.3 Bonding pressure smaller than 4MPa may as well not apply. The expectant data aways can not gained because small bonding pressure can not eliminate environal disturbance.4 By using Ag as intermediate layer , the diffusion of Ni and Fe from 316L stainless steel side to Zr-4 can be prevented and the formation of brittle intermetallic compounds like Zr₃Fe, NiZr₂, Ni₂Zr₃ can be avoided. Though some Ag atoms diffused into zircaloy side, AgZr is not too brittle, and it has some toughness. So themechanical performance like strength, deformability and toughness of the joints used Ag as intermediate layer are better than that of the Zr-4/316L bonding joints under the suitable conditions.