Pressureless solid state diffusion bonding of ferritic stainless steel honeycomb matrix

Abstract

A honeycomb matrix was prepared by winding a corru gated foil and a flat foil fabricated from 5Al–20Cr (wt-%) ferritic stainless steel. The interconnection between the corrugated foil and the flat foil was initiated as small bond islands which developed along the peaks of the corrugated foil because of the surface roughness of the foils. Each island gradually grew and united with others during diffusion bonding. The growth of the bond islands was controlled by two independent processes. One growth process was in the y direction, parallel to the contact zone between the corrugated foil and the flat foil. The other was in the x direction, perpendicular to the contact zone. It is suggested that the bonding is achieved by diffusional transport. The rate determining step of the y direction growth is controlled by volume diffusion in the high temperature region (>1473 K) but is replaced by another diffusional process as temperatures decrease below 1473 K. The dominant mechanism at low temperature (<1473 K) is suggested to be based on surface and interface selfdiffusion. It was found that the y direction bond growth process is much more important than the x direction neck growth sintering process in producing the honeycomb interconnection.