Abstract
In this study, fatigue crack growth (FCG) behavior of cemented carbide under the repeated thermal shock (RTS) was experimentally evaluated by using the thermal-shock experiment method developed by the authors. Tests were carried out using cemented carbide having two different WC crystal grain sizes. In addition, FCG behavior under rotating bending fatigue (RBF) test was investigated using the same cemented carbides. Then the FCG results obtained by the RTS test and the results of the RBF test obtained at stress ratio, R = -1, were compared with each other. Here, the stress ratio R is defined as, R = σmin/σmax; σmin and σmax are the minimum and the maximum stresses, respectively. From this comparison, it was found that the relation between the rate of fatigue crack growth (FCG) and the maximum stress intensity factor in the RTS tests was equivalent to the one obtained under the RBF tests at stress ratio of -1. From a practical point of view, this result is important as it indicates that it is not necessary to purposely perform RTS experiments. In this research, the effect of WC grain size on the short surface FCG behavior of the cemented carbide was also studied and discussed.
Highlights
It is well known that microcracks develop and grow in the tool due to the periodic thermal stress [1] that occurs during the intermittent cutting process
The fatigue crack growth (FCG) results obtained by the repeated thermal shock (RTS) test and the results of the rotating bending fatigue (RBF) test obtained at stress ratio, R = −1, were compared with each other
It was found that the relation between the rate of fatigue crack growth (FCG) and the maximum stress intensity factor in the RTS tests was equivalent to the one obtained under the RBF tests at stress ratio of −1
Summary
It is well known that microcracks develop and grow in the tool due to the periodic thermal stress [1] that occurs during the intermittent cutting process. For developing a new tool with an excellent resistance to the thermal shock, it is of importance to study and clarify the repeated thermal shock behavior of the cemented carbide. Such studies on the cemented carbides have been very few and limited as compared with other materials, such as ceramics [3] [4] [5] [6]. Ishihara et al [7] proposed the new thermal-shock experiment method that can accurately evaluate the thermal stress generated at thermal shock Using this new method, they clarified the FCG behaviors of silicon nitride [3] under the RTS tests
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