Diffusion bonding by hot isostatic pressing (HIP) was performed between Incoloy 909 and five different ceramics. Two of the ceramics were composites made from powder mixtures of Si3N4 and either 60 vol % TiN or 50 vol % TiB2, while three were monolithic materials, namely Si3N4 with 2.5 Wt% Y2O3 as a sintering additive, Si3 N4 without additives, and Si2 N2O without additives. A diffusion couple geometry was developed to facilitate the preparation of thin-foil specimens for examination by analytical electron microscopy (AEM). Diffusion bonding was performed by HIP at 927-degrees-C (1 200 K) and 200 M Pa for 4 h. The formation of reaction layers was very limited, being less than 1 mum in total layer thickness. Two reaction products were found by AEM; a continuous, very thin, (less-than-or-equal-to 1 00 nm) layer of fine TiN crystals at the initial ceramic/metal interface, and larger grains extending about 1 00-500 nm into the superalloy and forming a semi-continuous layer of a G-phase silicide containing mainly nickel, silicon and niobium.