This study investigates diffusion bonding of sialon and high-chromium steel. Sialon and 7.5-Cr steel were directly joined. The process was performed using hot press machine. Good joint was achieved due to the reaction of the sialon and the steel. The elemental inter-diffusion developed reaction layers in the interface of the bonded materials. The layers consisted of a thin and porous layer adjacent to the sialon and a thicker diffusion zone extended into the steel. Precipitates as reaction products of the sialon and the steel were found in the reaction layer in the sialon side. The reaction layers were more ductile then the bonded materials and helped to attain the joint. © 2011 Asian Network for Scientific Information.