A new family of reaction bonded ceramics for armor applications

Reaction bonded SiC has existed for many years. It is produced by reactively infiltrating a preform consisting of SiC and carbon with molten Si. During the infiltration process, the Si and carbon react to form SiC. Thus,the finished body consists of the original SiC, reaction-formed SiC, and residual Si. Historically, reaction bonded SiC processes are designed such that high levels of reaction-formed SiC are produced. With high levels of reaction formed SiC, the resultant microstructure has a fully interconnected (coarse) SiC phase that provides good performance in traditional ceramic applications (e.g., wear, corrosion, high temperature, creep). Within the past few years, new applications for ceramics have emerged in the semiconductor industry (e.g., wafer chucks, wafer handling arms, process chambers). These applications have different requirements than those for which reaction bonded SiC was previously developed. For instance, the semiconductor applications do not require wear or creep resistance, but do require excellent net shape processing characteristics and a fine microstructure suited to machining of minute details to high tolerance. To this end, a novel approach to reaction bonded SiC was taken. Preforms that possessed a very high content of less than 50 micron SiC particles and a low carbon content were produced with a resin molding process. Upon infiltration, little reaction occurred. This resulted in minimal process shrinkage or distortion; and a microstructure with little coarsening and low levels of residual stress. Such a material was found to be well suited to near net shape production and machining to extremely precise tolerances for semiconductor applications. This novel reaction bonded SiC ceramic was evaluated for utility in armor applications. The product was shown to possess good ballistic properties and the ability to be produced to the desired tolerances without the need for machining.