CHEMICAL-REACTIVITY OF NICKEL AND NICKEL-BASED ALLOYS WITH A SIALON CERAMIC

At the high cutting speeds typical for machining with ceramics and the concomitant high temperatures generated at the cutting edge and the rake face of the tool, chemical interaction between tool and workpiece material becomes the predominant mode of tool wear, To obtain more information concerning this chemical interaction mechanism, the chemical interaction of a beta'-O' SiAlON ceramic with pure nickel, Inconel 600, and Nimonic 105 is studied. The chemical reactivity was assessed by studying ceramic-alloy interaction couples after exposure at elevated temperatures (1100-1200 degrees C) for times long enough to be able to characterize the interaction layer. At 1200 degrees C, the beta'-O' SiAlON ceramic dissociates in contact with pure nickel, Silicon from the dissociation of the ceramic dissolves and diffuses into the nickel, whereas Al and O form Al2O3 particles. At the interface, a nitrogen pressure is built up, Inconel 600 is very reactive with the SiAlON ceramic, with the formation of molten silicides at 1200 degrees C, Cr3Ni2Si, Al2O3, and Ni31Si12 are the major reaction products, The reactivity of Nimonic 105 is less than that of pure nickel because of the formation of a continuous protective TiN layer at the ceramic-metal interface.