Wear mechanisms of gradient ceramic nozzles in abrasive air-jet machining

The nozzle is the most critical part in abrasive air-jet machining equipment. Ceramics, being with high wear resistance, have great potential as abrasive air-jet nozzle materials. In this paper, a (W,Ti)C/SiC gradient ceramic composite was developed to be used as nozzle material. The erosion wear behavior of the (W,Ti)C/SiC gradient nozzle was investigated and compared with a conventional ceramic nozzle. Results showed that the gradient ceramic nozzles exhibited an apparent increase in erosion wear resistance over the conventional ceramic nozzles. The mechanism responsible was found to be that the tensile stresses at the entry region of the nozzle were greatly reduced when compared with the conventional nozzle. This effect may lead to an increase in resistance to fracture, and thus increase the erosion wear resistance of the gradient nozzle. It is indicated that gradient structures in ceramic nozzles are effective to improve the erosion wear resistance of conventional ceramic nozzles in abrasive air-jet machining. (c) 2007 Elsevier Ltd. All rights reserved.