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This paper presents the micro-shot peening of zirconia (ZrO)-advanced ceramics applicable for bio-medical, dental, automotive and aerospace sectors. A ZrO-advanced ceramic was micro-shot blasted with selected parameters as a first-step investigation focused on the topography, microstructure, surface hardness and the surface fracture toughness ( K) characteristics. A new technique of micro-blasting was conducted using a portable shot blaster. A white-light interferometer, scanning electron microscopy and Vickers indentation technique were employed for the analysis. This was followed by determining the K using an empirical equation. Surface roughness was improved by 34 % after micro-shot blasting treatment. No surface cracking was present which generally exists due to the brittle nature of the ceramic. The hardness, however, reduced by 5.6 % with a reduction in the Vickers crack length of 9 %. This improved the K by 3 % when comparing the micro-shot peened surface to the original, as-received surface. It is difficult to conclude if the ZrO-advanced ceramic has undergone plastic deformation and the movement of dislocations increased to strengthen the ZrO ceramic at this stage. However, based on the results, it can be predicted that a level of surface compression was induced beneath the micro-shot peened layer as indicated from the result of the surface topography and integrity. This would justify the hardness modification and the enhancement in K. [ABSTRACT FROM AUTHOR]

Effect of YNbO4 addition on the fracture toughness and stress-strain characteristics of ZrO2(3Y) ceramics was investigated using micro-indentation, X-ray diffractometry and in-situ compression-diffraction techniques in the present work. X-ray diffraction patterns show that sintering of YNbO4 and ZrO2(3Y) mixture results in formation of a solid solution, and the tetragonality of ZrO2(3Y) ceramics increases with the content of YNbO4. The ratio of 002t to 200t peak intensity in X-ray diffraction spectra of the specimens changes significantly after a grinding process at low fractions of YNbO4 (less than 5 mol%) and approaches to a constant value as the content of YNbO4 is higher than 5 mol%, implying that the addition of YNbO4 reduces the domain switchability of the ZrO2(3Y) ceramics. Fracture toughness of modified-ZrO2(3Y) specimens with the same heat treatment conditions could be greatly enhanced by an appropriate addition of YNbO4. In addition, stress-strain curves of YNbO4-modified ZrO2(3Y) specimens exhibit an extraordinary elastic behavior. Data of in-situ loading-diffraction experiment show that an unidentified stress-induced transformation occurs and the peak intensity varies with the stress conditions. Analysis of the stress-strain characteristics and X-ray diffraction results suggest that the fracture toughness of the specimens cannot be simply attributed to the t-to-m phase transformation. [ABSTRACT FROM AUTHOR]

Indentation fatigue testing is carried out for four kinds of zirconia ceramics; 6Y-FSZ, 3Y-TZP, Mg-PSZ and Ce-TZP; which have different strengthening-toughening mechanisms one another. Each material shows different indentation fatigue behavior. Large sized surface chipping is produced easily in early cycles for non-toughened 6Y-FSZ, while 3Y-TZP toughened by anelasticity has high resistance against chipping. There is a possibility that anelastic characteristic works as resistance against indentation fatigue damage. Stress induced phase transformation also improves fatigue damage, but this effect depends on the extent of transformation and/or occurrence of microcracking. [ABSTRACT FROM AUTHOR]