Ta及Ta-W合金真空渗碳工艺研究

Vacuum Carburization Process of Ta and Ta-W Alloys

对-Ta及Ta—W合金进行渗碳处理，在表面获得一定厚度的渗碳层，可以有效的提高其使用性能。对Ta及Ta—W合金进行真空渗碳处理，利用X射线衍射仪（XRD）、扫描电镜（SEM）和金相显微镜（OM）研究了不同渗碳时间和渗碳温度对样品渗碳结果的影响规律，分析了合金元素W对Ta—W合金渗碳结果的影响。结果表明：在1300℃下渗碳5h，纯Ta渗碳层表面物相为Ta，TaC及Ta2C三相共存；随着渗碳时间的延长，渗碳层中Ta及Ta2c含量逐渐减少，渗碳10h时，Ta及Ta2C相消失并全部生成TaC相。在本文的渗碳条件下，W不与C原子发生反应生成碳化物，而是仍以溶质原子的形式固溶于晶体内部。在1300～1500oC范围内，随渗碳温度升高，渗碳层厚度增加；随着渗碳时间的延长，渗碳层厚度增加；提高渗碳温度有利于TaC相的形成；1500qc下渗碳10h，钽的渗碳层厚度可达35—40μm。在1500℃下渗碳5h，Ta渗碳层厚度约20μm，Ta-2．5％W为10～12μm，Ta-7．5％W渗碳层厚度仅为7—8μm，表明随着钽钨合金中W含量的增加，渗碳速率降低，相同时间内获得的渗碳层厚度越薄。

A carburized layer of Ta and Ta-W alloys with a certain thickness was obtained by carburizing, which could improve the performance effectively. Vacuum carburizing technology was performed on Ta and Ta-W alloys to explore the rules of experimental re- suits under different time and temperature using X-ray diffraction （ XRD）, scanning electron microscope （ SEM ） and optical micro- scope （OM） , and the effect of alloying element W on experimental results of Ta-W alloys was analyzed. The results showed that the re- action was incomplete after carburizing at 1300 ℃ for 5 h, and the phase composition of tantalum carburized layer contained Ta, TaC and Ta2 C. The contents of Ta and Ta2 C gradually decreased with the extension of time, and eventually both Ta and Ta2 C disappeared and TaC was produced totally after earburizing for 10 h. Under the carburizing conditions, W did not react with C, while W still dif- fused in crystal to from solid solution. The thickness of carburized layer increased with the increase of temperature between 1300 and 1500 ℃. The thickness of carburized layer was increased with the extension of time. Increasing the earburizing temperature was favora- ble for production of TaC. The thickness of Ta carburized layer could reach 35 - 40 μm after carburizing at 1500 ℃ for 10 h. The thickness of Ta carburized layer was 20 μm after earburizing at 1500 ℃ for 5 h, while the carburized layer thickness of Ta-2.5% W and Ta-7.5% W were 10 - 12 μm and 7 -8 μm, respectively. The result suggested that carburizing rate was reduced with the content in- crease of W in Ta-W alloys, which led to a thinner carburized layer.