Sintering Silicon Nitride to Form Near Net Shape Cutting Tools

该项目致力于开发一种烧结氮化硅陶瓷系统，该系统在1000oC下具有至少70,000磅/平方英寸的横向抗折强度，致密到理论密度的99%，并作为可转位刀具成形为近净形状。最终目标是在氮气压力的一个气氛下完成具有所需显微结构的全密度烧结。某些烧结限制限制了成分的选择。然而，可以通过在显微组织-烧结极限内致密化的成分来获得最佳性能。也有可能某些成分需要两步烧结过程才能达到99%的理论密度。这项研究的潜在好处将是对氮化硅陶瓷系统的烧结机理有一个基本的了解，并通过使用烧结氮化硅刀具加工灰口铸铁来提高生产率和节约成本。

This project deals with the development of a sintered silicon nitride ceramic system having a transverse rupture strength of at least 70,000 psi at 1000oC, densified to 99% of the theoretical density, and formed to near net shape as an indexable cutting tool. The eventual goal is to accomplish sintering to full density with the desired microstructure at one atmosphere of nitrogen pressure. Certain sintering limits restrict the compositional choices. However, optimal properties may be obtained by compositions that can be densified within the microstructure- sintering limits. It is also possible that certain compositions require a two-stage sintering process to achieve 99% theoretical density. Potential benefits from this research would be a fundamental understanding of the sintering mechanism of the silicon nitride ceramic system, and the increased productivity and cost-savings from the use of sintered silicon nitride cutting tools in machining gray cast iron.