| Popis: |
For engineering ceramics, cracks produced in preparation process, i.e. sintering and surface finishing, have a profound impact on the mechanical strength and wear. Under cavitation loading, the flaws on the surface and subsurface are preferentially eroded. In this paper, artificial cracks are introduced on WC ceramic by indentation of a Vickers indenter at a load of 10 kgf. Five positions on the cavitation eroded area are selected. The average length of the cracks is 71.6 mm. The cavitation erosion tests are terminated at 1, 3, and 5 min to reveal the evolution of cracks. A single pattern for the evolution of cracks is recognized. Two new cracks at the tip of indentation cracks first nucleate and then propagate (accompanied by pullout of grains). The angle between the two new cracks ranges from 30° to 45°. The evolution of adjunct two groups of cracks gives birth to local breakout finally. Steps which are provided limited resistance to breakout are observed. The nucleation and propagation of the four indentation cracks do not always occur simultaneously. |
