Good surface integrity is frequently required for structural ceramic components, since the lifetime of a ceramic component is in most cases determined by its surface features. In this study, the surface integrity of electro-discharge machined, ultrasonic machined, and diamond saw cut ceramic composites has been investigated and compared. The surface roughness, hardness, and topography of the machined surface were examined. Flexural strength and its distributions were used to evaluate the e

In ultrasonic machining (USM), the material is removed primarily by repeated impact of the abrasive particles, and the material removal rate (MRR) and surface integrity are influenced by various factors including the material parameters of the workpiece materials. In this study, effect of the properties and microstructure of the workpiece materials on the MRR in ultrasonic machining of alumina-based ceramic composites was investigated. The distributions of strength of the ultrasonic machined specimens were used to evaluate the surface integrity. Results showed that fracture toughness of the ceramic composite played an important role with respect to MRR. In USM of whisker-reinforced alumina composites, the MRR depended on the whisker orientation. Studies of strength distributions of alumina-based ceramic composites machined by USMdemonstrated that the flexural strength varied narrowly from the mean value, and the composites with high fracture toughness showed higher Weibull modulus.

Sand blasting nozzle is the most critical part in the sand blasting equipment. Ceramics being with high wear resistance have great potentials as the sand blasting nozzle materials. In this paper, monolithic B4C andAl2O3/(W,Ti)C ceramic composite were developed to be used as nozzle materials. The wear behavior of nozzles made from these ceramic materials was compared by determining the cumulative mass loss and the erosion rates. Effect of the factors that influence the nozzle wear was investigated. Results showed that the hardness of the nozzles plays an important role with respect to its erosion wear in sand blasting processes. The monolithic B4C nozzles being with high hardness exhibited lower erosion rates, while the Al2O3/(W,Ti)C nozzles with relative low hardness showed higher erosion rates under the same test conditions. Studies of the worn surface of the ceramic nozzles demonstrated that monolithic B4C nozzles exhibited a brittle fracture induced removal process, while Al2O3/(W,Ti)C nozzles showed mainly a plowing type of material removal mode.

Good surface integrity is frequently required of struc-tural ceramic components, since the lifetime of a ceramic component is, in most cases, determined by its surface features. In this study, two mechanical surface treatments, i.e. ultrasonic and abrasive blasting sur-face finishing, have been introduced to the surface of electrodischarge machined ceramic composites to improve their surface integrity. T he surface roughness, hardness, and topography of the ceramic composites were examined after electrodischarge machining (EDM) and surface treatment. T he eVect of surface integrity on the strength and its distribution was investigated. Results show that ultrasonic and abrasive blasting surface finishing can produce an improvement in both flexural strength and Weibull modulus, and are two eVective procedures to improve the surface integrity of the EDM ceramic composites.

In this paper, Al2O3/TiB2 ceramic cutting tools with different TiB2 content were produced by hot pressing. The fundamental properties of these ceramic cutting tools were examined. Dry high-speed machining tests were carried out on hardened steel. The tool wear, the cutting temperature, the cutting forces, and the friction coefficient between the tool and the chip were measured. It was shown that both the wear rates and the friction coefficient at the tool-chip interface of Al2O3/TiB2 ceramic cutting tools in dry high-speed machining of hardened steel were reduced compared with that of in low-speed machining. The mechanisms responsible were determined to be the formation of a self-lubricating oxide film on the tool-chip interface owing to the tribological-chemical reaction by the elevated cutting temperature. The composition of the self-lubricating film was found to be the oxidation product of TiB2 grains, which serves as lubricating additive on the wear track of the tool rake face. The appearance of this self-lubricating oxide film contributed to the improvement in wear resistance and the decrease of the friction coefficient. This action was even more effective with higher TiB2 content. Cutting speed was found to have a profound effect on the self-lubricating behavior. In dry low-speed machining of hardened steel, the Al2O3/TiB2 tools showed mainly adhesive and abrasive wear. While in dry high-speed machining, oxidation wear of the ceramic tools was the dominant mechanism due to the very high cutting temperature. No oxide film was formed on the tool–chip interface while machining in nitrogen atmosphere, and the tool wear resistance was correspondingly decreased.