采用不含氮的硬质合金原料, 在梯度烧结工艺前添加一步微压氮化烧结(氮气分压为0.5 kPa)工艺, 然后于1 420,1 450,1 480 ℃下烧结1 h制备了脱β层梯度硬质合金; 另在无微压烧结工艺下制备了均质结构硬质合金; 分别采用SEM、XRD及EDS等分析了合金的组织、相组成及成分分布。结果表明: 在上述微压烧结工艺下制备的梯度硬质合金中脱β层厚度分别为8, 13, 24 μm; 该脱β层梯度硬质合金的物相和成分分布规律与采用含氮硬质合金原料制备的基本一样, 即脱β层中仅含WC及钴相, 心部为WC、(Ti, W)C和钴相, 脱β层中的钛元素含量基本为零, 钴元素的含量高于心部的平均含量, 钨元素含量的变化不大。

Using the cemented carbide raw materials without nitrogen, the graded cemented carbide with cubic carbide free layer (CCFL) in the surface zone was prepared by means of gradient sintering at 1 420,1 450,1 480 ℃ for 1 h, respectively, where one micro pressure (0.5 kPa) nitriding sintering (MPNS) step was added prior to usual gradient sintering procedure. In addition, the cemented carbide with heterogeneous structure was prepared without MPNS. The microstructure, phase composition and element distribution of the cemented carbides were investigated by SEM, XRD and EDS. The results show that, the thickness of cubic carbide free layer was 8,13,24 μm under the above sintering process conditions. The phases and chemical compositions distribution regular of the graded cemented carbide with CCFL were basically same with that of the graded cemented carbide prepared by raw materials with nitrogen, that is to say,there were only two phases including WC and Co phases in the CCFL, whereas there were WC, (Ti,W)C and Co phases in the core zone, and the titanium content in the CCFL was close to zero, cobalt content was apparently higher than that in the core zone, whereas there was only tiny fluctuation of tungsten content.