冷却速度对WC-0.5%TaNbC-6%Co合金组织结构及性能的影响

Effects of Cooling Speed on Microstructure and Mechanical Properties of WC-0.5%TaNbC-6% Co Cemented Carbide

本文采用SEM-EDS、SEM-EBSD等手段研究了冷却速率对WC-0.5%TaNbC-6%Co硬质合金组织结构和性能的影响,阐述了冷却速度对TaNbC固溶体形貌的影响规律,探讨了其作用机理。实验结果表明,随着冷却速度的增加,硬度增加,KIC呈小幅下降趋势。烧结合金表面Co含量随冷却速度的增加急剧减少。随着冷却速度增加,TaNbC固溶体聚集区域面积缩小,TaNbC固溶体聚集点增多,TaNbC晶粒间的取向差异增大。增加冷却速度可以增加液相过冷度,使得临界形核能降低,导致临界形核尺寸减小,同时形核率增大,其析出物将会体积缩小、数量增多,使得TaNbC固溶体呈分散分布。车削1Cr18Ni9Ti不锈钢实验结果表明,随着冷却速度的增加,WC-0.5%TaNbC-6%Co合金刀片的切削寿命呈先增加后下降趋势,在40℃/min时耐磨寿命最高。在相近的强度和韧性下,合金基体硬度的提高、TaNbC固溶体聚集改善以及合金基体组织结构均匀性提高,导致合金切削寿命提升。

The effects of cooling speed on the microstructures and mechanical properties of WC-0.5 Ta Nb C-6 Co alloy were studied by SEM-EDS and SEM-EBSD. The influence of cooling rate on the morphology of Ta Nb C aggregations was expounded, and the formation mechanism was discussed. The results indicate that the hardness increases with the raise of cooling speed, while the fracture toughness slightly decreases. The surface Co content decreases with the increase of cooling speed. With the increase of cooling speed, the area of Ta Nb C aggregation is shrunken, and the numbers of Ta Nb C aggregation are increased. Besides, the orientation difference of Ta Nb C grain increases with the increase of cooling speed.The super cooling degree of liquid-Co increases with the increase of cooling speed. As a result, the critical nucleation energy and critical nucleation radius decrease and the nucleation rate increases. As a consequence, the Ta Nb C aggregations can be alleviated or even eliminated with the increase of nucleation number and the shrink of Ta Nb C aggregation area. The cutting tests demonstrate that the cutting life increases with the increase of cooling speed and the insert which sintered with 40 ℃/min cooling speed has the longest wearing life. While the insert wearing life decreases with the further increase of cooling speed. The increase of hardness, with the improvement of Ta Nb C aggregations and microstructure homogeneity, are beneficial for the improvement of insert performance.