Carbide Tungsten-cobalt Ceramics Subsurface Crack's Extent Forecast Model's Establish

With many excellent physical mechanics property, nanostructured ceramic coatings will be extensively used in industry. But the material is difficult to be machined, and it has to be ground in manufacture filed, and grinding cracks which is a kind of scathe maybe easily produced in the process of grinding. Therefore, grinding cracks, subsurface scathe and machining parameter's effect to are worthwhile to be studied. According to the fracture mechanics of ceramics the extending dynamics factors of subsurface crack is analysed. A formula for critical grinding depth of a single grain of nanostructured ceramic coating under no-cracks is founded, and for validating the formula the experiment which a diamond sclerometer scratches nanostructured ceramic (WC/12Co) coatings's surface has been made. According to the formula, the extending scope for subsurface crack of the material can be analysed quantifacationally. Another important content in this paper is that a model for the cracks is constructed using CDM model, the ANSYS software is used to simulate to the real machining conditions, and the result is used to compare to the experiment. Investigations had been processed by comparing parameter for sclerometer (grain) of different shape of top, relatively movement velocity of the sclerometer and the material and the scratching depth. Some meaningful conclusions had been made: 1. In the test, a form of subsurface crack is relative to the sclerometer's (or grain's) shape, when the top of the sclerometer is sharper the crack is easier form. 2. The hardness and the fracture toughness of the material is dominant in the forming of crack, the higher the values of hardness is the easier the crack forms, and the higher the value of fracture toughness is the more difficult the crack forms. 3. According to the comparion of the simulation datum to the experiment datum, ANSYS software can be used to predict grinding crack. The formula, founded in this paper after the research to the subsurface of nanostructured WC/12Co coating, can be used to predict the grinding crack of the material. The formula, which can guide the precision grinding nanostructured ceramic coatings and predict the grinding process, is obtained. A formula for critical depth is developed which nanostructured WC/12Co coating is machined by a single grain under no-crack is produced in the subsurface.