Mechanical surface treatments of electro-discharge machined (EDMed) ceramic composite for improved strength and reliability

To obtain size specification, ceramic composites often need to be machined, and these processes may lead to a decreased strength and reliability especially for electro-discharge machining (EDM). In this paper, two mechanical surface treatments, i.e. ultrasonic machining (USM) and abrasive blasting, have been introduced to restore and improve these properties for the electro-discharge machined (EDMed) surfaces of the toughened and electroconductive Al2O3/TiC/Mo/Ni ceramic composite. Comparison of the flexural strength of EDMed and modified specimens revealed that the modified specimens yielded an apparent strengthening with a concurrent increase in Weibull modulus. Microstructure analysis showed that the EDMed specimens of this composite had suffered severe surface damage. Abrasive blasting and ultrasonic machining are two effective procedures to reduce this damage and to minimize the surface contribution to fracture probability.