Diffusion bonding stainless steel to alumina using aluminium interlayers

A study has been conducted to identify the effects of fabrication temperatures pressures, times and other variables on the strengths of diffusion-bonded joints between alumina and BS321 stainless steel produced using aluminium foil interlayers. The strengths of the alumina-aluminium and steel-aluminium interfaces were found to be influenced differently by some fabrication parameters, thus increasing the fabrication temperature promoted alumina-aluminium bonding but also accelerated the growth of ultimately weakening intermetallic layers at steel-aluminium interfaces. It was concluded that the optimum conditions for bonding BS321 stainless steel to alumina could be achieved by using a 0.5 mm aluminium foil, applying a 50 MPa pressure for 30 min in an evacuated chamber at 625° C. In discussing the results of this study, attention is paid to the problems or advantages of using foils and metal components other than aluminium or BS321 steel and particular note is taken of thermal expansion mismatch effects.