ENHANCEMENT OF CERAMIC-TO-METAL ADHESIVE BONDING BY EXCIMER-LASER SURFACE-TREATMENT

A silicon nitride (Si3N4) based ceramic cutting material and a structu ral alloy steel (SAE 4340) were surface-treated using a 800 mJ KrF exc imer laser with an aim to improve the ceramic-to-metal bond strength. For these two materials, the effects of laser energy density and the n umber of pulses upon the surface morphologies of the laser-treated sur faces to be joined were examined. Conical surface microstructures were generally observed on the laser-treated surfaces of the Si3N4 materia l, and the number of conical features was found to be significantly in fluenced by the laser energy density. Moreover, the results of XPS hav e shown that the surface chemistry of the ceramic was altered after be ing laser treated. On the other hand, excimer laser treatment had caus ed the alloy steel surfaces be melted and resulted in some ''beach-mar k'' features. However, the laser energy density has little effect on t he overall surface morphology and the roughness of the treated surface s. Shear tests were performed on adhesive bonded samples of the laser- treated ceramic and alloy steel. Significant improvement in adhesion s hear strength was obtained for the laser-treated samples as compared w ith those tested in the as-received and mechanically abraded condition s. The required laser operation condition for achieving good shear joi nt strength was discussed.