Surface treatment of wire electro-discharge machined engineering ceramics by abrasive blasting

Abstract

The surface integrity of electro-discharge machined engineering ceramics and their surface modification by abrasive blasting have been investigated in this study. Flexural strength was used for evaluating the effect of the two machining processes on the surface of machined specimens. The distributions of strength data were further analyzed by the Weibull statistical method to give a quantitative measure of the surface integrity. The test results show that the mean flexural strength values of wire electro-discharge machined Syalon 501 ceramics are considerably low, only about 33-52% of the original value of the material, 825 MPa. The value of the Weibull modulus, m, is very low, in the range of 4.2-8.8. Wire electro-discharge machined ceramic surfaces are of poor surface integrity and low reliability, so it is necessary to treat them before practical application. After undergoing abrasive blasting, the mean flexural strength values were found to be 20-25% higher than those of wire-EDM pre-machined specimens. The calculated Weibull modulus, m, is in the range of 14-15.5, which is much higher than that of wire-EDM pre-machined specimens, 8.1. The test results show that with most of the abrasive blasting conditions, the ceramic specimens behave fairly consistently and their properties vary narrowly from the mean value. The Weibull modulus, in, based on these small populations, increased with decreasing compressed air pressure and grain size of the abrasives. Abrasive blasting is an effective machining procedure to modify ceramic surfaces subjected to wire-EDM.