疲劳预裂SENB法测试硬质合金的断裂韧性

Research on Fatigue Precracking SENB to Determin Fracture Toughness of Cemented Carbide

断裂韧性测试方法的稳定性及准确性一直为硬质合金工作者所关注。本文利用三点弯曲疲劳预制裂纹的单边切口梁(SENB)法,测定了5种不同WC晶粒尺寸和Co含量的硬质合金试样的断裂韧性K_(IC),并与线切口的SENB法测定的K_(IC)值进行对比研究。试验结果表明:与不预制裂纹的线切口SENB法相比,疲劳预裂SENB法测定K_(IC)值与合金本征断裂韧性值吻合度高,偏差极小。线切口的SENB法切口根部曲率半径难以达到理论所需的初始裂纹尖端半径,疲劳预裂SENB法预制裂纹过程稳定可控,测试数据准确性高,是评价硬质合金断裂韧性较为理想及有效的方法。此外,合金的断裂韧性K_(IC)值随Co含量和WC晶粒度的增加而提高。

The stability and accuracy of fracture toughness testing method have been highly attracted by the researchers in the field of cemented carbide. In this research, the single edge notch beam （SEN/l） specimen with fatigue precrack were used to determine the fracture toughness of the cemented carbide with five different combinations of WC grain size and Co content, and the results were compared with the measured Kic values of SENB specimen with line incision. The results show that compared with the measured Klc values by the SENB method without precrack, the measured values of the SENB method with precrack are highly corresponding to the intrinsic fracture toughness for the experiment alloy. The SENB method with line incision can not accurately and effectively evaluate the fracture toughness of the experiment alloy due to the defective notch root radius, the SENB with fatigue preerack is an ideal and effective method to evaluate the fracture toughness of the cemented carbide due to its stable and controllable precracking process and the accurate test data. Moreover, the fracture toughness of the experiment alloy is enhanced with the increase of the cobalt content and WC grain size.