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

S. Jahanmir, T. Strakna, G. D. Quinn, R. N. Kopp, S. C. Yoon, and K. V. Kumar, “Effect of Grinding on Strength and Surface Integrity of Silicon Nitride: Part II,” 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) 279-291.

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 involving high material removal rates. The resulting ground surfaces were investigated with a three-dimensional profiling instrument and a scanning electron microscope. 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 characterize and determine the location of the fracture-initiating flaw in each specimen. Varying the volumetric removal rate in surface grinding from 310 to 516 cu mm/min for RBSN and from 310 to 1737 cu mm/min for SRBSN by employing creep feed grinding conditions was found to have no significant effect on the characteristic strength of these materials. However, one of the grinding conditions, which used spark-out, reduced the Weibull modulus, i.e., increased the variation in flexure strength. The results also showed that surface roughness and topography were affected by the grinding conditions.


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