MEASUREMENT OF BULK RESIDUAL-STRESSES IN MOLYBDENUM DISILICIDE STAINLESS-STEEL JOINTS USING NEUTRON-SCATTERING

Neutron diffraction was used to measure the bulk residual strains in m olybdenum disilicide (MoSi2)-316L stainless steel joints. The joints w ere produced by brazing disks of MoSi2 and 316L stainless steel along with an interlayer, using Cusil(TM) as the braze. This study explored the physical parameters of the interlayer on the average phase strains in the MoSi2 and 316L stainless steel. The effect of the coefficient of thermal expansion was explored by using three different interlayer materials; niobium, nickel, and nickel-iron. The residual strains in M oSi2 decreased significantly in both radial and axial directions with increasing niobium interlayer thickness. Residual strains were relativ ely insensitive to changes in the 500 mu m thick interlayer material. Finite element modeling results were corroborated by the neutron measu rements on the joints allowing inferences to be drawn concerning the p reference of the interlayer material. The results illustrate the impor tance of the ductile interlayer in the successful fabrication of MoSi2 -316L stainless steel joints. (C) 1998 Acta Metallurgica Inc.