Efficient Densification of Fine-Grained Ceramics by Hybrid (RCS-Plus-HIP) Processing

Abstract

ABSTRACTIn this paper, we consider certain technological and economic advantages associated with rate controlled sintering (RCS) as the critical first step in a two-step hybrid densification cycle: RCS-plus-HIP. With proper combinations of(a) powder processing (to obtain narrow initial particle size distribution and high green density) and (b) carefully optimized RCS sintering profile (to assure effective pore closure with minimal grain growth), one can readily produce technically dense (gas-tight) sintered ceramic components that can then be rather easily HIPed to full density with very little additional grain growth.The experimental background and underlying concepts for RCS are briefly reviewed, and are related to the broader issue of establishing and maintaining control of microstructural evolution during densification processes, including those that are best concluded in the high pressure gas atmospheres typically employed for hot isostatic pressing (HIP). To illustrate these points, some examples of RCS-plus-HIP processed oxide ceramics – dense, optically translucent and/or transparent, yet also quite uniformly fine-grained – are shown and discussed.