Diffusion bonding .structural peculiarities of mating surfaces for different methods of surface preparation

摘要

Surface and sub-surface layers of the NP-2 nickel billet after different methods of preparation of the mating surface or diffusion bonding are investigated by optical diffraction electron microscopy. It is shown that after preparation for bondingthe sub-surface layers have a fine-dispersed structure with disoriented sub-structural elements of up to 10° in size. The blocks increase in size and the disorientation angle decrease with a distance from the surface. The total depth of distortion of the structure is from 180 to 40 microns in he case of rough and fine treatments, respectively. The level of the effective deformation, depending upon an intensity If the treatment, is about 110...240 %. Structural changes in the mating surfaces caused bymachining contribute to hardening the sub-surface layers. The total Increase in yield strength is 6...8 times higher than yield strength of parent metal. The latter circumstance can have an effect on plastic deformation of metal in the contact zone during the process of diffusion bonding and can result in the local gradients of mechanical properties of the bond.