Effect of Grinding on Strength and Surface Integrity of Silicon Nitride: Part I

S. Jahanmir, T. Strakna, G. D. Quinn, H. Liang. R. Allor, and R. West, “Effect of Grinding on Strength and Surface Integrity of Silicon Nitride: Part I,” Machining of Advanced Materials, Proc. of the Int. Conf. on Machining of Advanced Materials, S. Jahanmir (Ed.), NIST SP 847, Government Printing Office, Washington, DC (1993) 263-277.

Grinding is often the method of choice for machining structural ceramics and has a high potential for large-scale production and automation. Because there are few guidelines available for grinding ceramics, a conservative approach is usually used to minimize grinding-induced damage. With this approach, machining time is high, which increases cost. The purpose of this paper is to report data and information on the effect of grinding on strength of two types of silicon nitride. Standard flexure specimens, made from a reaction- bonded and a sintered reaction-bonded silicon nitride (RBSN and SRBSN), were surface ground in the longitudinal direction under three different conditions. The resulting ground surfaces were characterized and four-point flexure tests were performed on the specimens and Weibull parameters were calculated to determine the effect of the different grinding conditions on flexure strength. Fractography was performed on the specimens after testing to determine the location and to characterize the fracture origin in each specimen. The results showed that varying the material removal rate by a factor of 20 had no significant effect on the characteristic strength or the Weibull modulus of four-point flexure specimens. This implies that material removal rates higher than those currently used for grinding these two types of silicon nitride materials may be possible without strength degradation.

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