화학공학소재연구정보센터
Materials Science Forum, Vol.426-4, 2321-2326, 2003
Near net shape, low cost ceramic valves for advanced engine applications
Future gasoline and diesel engines with electro-hydraulic or electro-mechanical valve control systems require the development of lighter valves to achieve the best results in terms of increased performances, lower fuel consumption and overall efficiency. Ceramic materials can adequately satisfy the required mechanical and thermal properties, nevertheless they still lack as far as manufacturing costs are concerned. Objective of the work was the development of a low-cost forming and sintering process, to produce near-net shape ceramic valves thus requiring very low finishing operations and significantly minimizing material waste. Between available technical ceramic materials, silicon nitride has been chosen to replace conventional steels and Ni-based alloys for the exhaust valves application. The work was then devoted to (i) the selection of the best starting materials composition, taking into account the requirements of a cost effective and high volume production, (ii) the development of an innovative pressure-injection molding process to produce near-net shape parts via a thermosetting feedstock and (iii) the optimization of a proper pressure-less sintering route to obtain cost-competitive, real scale components with adequate final density and mechanical properties.