Pressureless solid state diffusion bonding of ferritic stainless steel honeycomb matrix

A honeycomb matrix was prepared by winding a corrugated foil and a flat foi l fabricated from 5Al-20Cr (wt-%) ferritic stainless steel. The interconnec tion between the corrugated foil and the pat foil was initiated as small bo nd islands which developed along the peaks of the corrugated foil because o f the surface roughness of the foils. Each island gradually grew and united with others during diffusion bonding. The growth of the bond islands was c ontrolled by two independent processes. One growth process was in the y dir ection, parallel to the contact zone between the corrugated foil and the pa t foil. The other was in the x direction, perpendicular to the contact zone . It is suggested that the bonding is achieved by diffusional transport. Th e rate determining step of the y direction growth is controlled by volume d iffusion in the high temperature region (>1473 K) but is replaced by anothe r diffusional process as temperatures decrease below 1473 K. The dominant m echanism at low temperature (<1473 K) is suggested to be based on surface a nd interface selfdiffusion. It was found that the y direction bond growth p rocess is much more important than the x direction neck growth sintering pr ocess in producing the honeycomb interconnection.