Sinter-Canning for Hip-Processing of Silicon Nitride

A new sinter-canning method has been developed for the coating of silicon nitride parts prior to hot-isostatic pressing. This method is based on thick-film technology. Using sol-gel methods different shapes of silicon nitride have been coated with an alumina or zirconia gel. After drying and sintering a dense layer of the oxides are formed, suitable as a ceramic canning material. Following the HIP-process, dense silicon nitride is achieved with a surface layer containing the aluminium or zirconium ions in a crystalline phase. This method of sinter-canning prevents the formation of glassy phases and can be used for a variety of ceramics to be densified by hot-isostatic pressing.