Sintering Silicon Nitride to Form Near Net Shape Cutting Tools

该项目涉及一种烧结氮化硅陶瓷系统的开发，该系统在1000℃下的横向断裂强度至少为70000 psi，密度达到理论密度的99%，并形成近净形状作为可转位切削工具。最终目标是在一个大气压的氮压力下完成烧结到具有所需微观结构的全密度。某些烧结极限限制了材料的选择。然而，在微观结构-烧结极限内致密化的成分可以获得最佳性能。也有可能某些成分需要两阶段烧结过程才能达到99%的理论密度。这项研究的潜在好处是对氮化硅陶瓷系统烧结机制的基本理解，以及在加工灰铸铁时使用烧结氮化硅刀具提高生产率和节省成本。

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.