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本工作证实WC-Co系硬质合金通过热处理可以提高其抗弯强度。所增加的抗弯强度决定于合金中钴的含量,钴含量越高的合金,其抗弯强度的增加重也就越多。主要是由于淬火热处理抑制了高温稳定的面心立方钴相转变成密排六方钴相。 本实验还采用差热分析仪测定了WC—Co系合金在加热过程中,密排六方钴相转变成面心立方钴相的相变温度。发现其相变温度随合金中钴含量的增加而升高,如YG8是742℃,YG15是770℃,YG20是821℃,这是由于高钴合金的粘结相在升温过程中有较高的钨含量。 本实验中还发现,烧结后低钴硬质合金要高于高钴硬质合金的粘结相中的钨含量,因为低钴硬质合金的烧结温度通常是高于高钴硬质合金,一般说来烧结温度越高,则粘结相中的钨含量也就越高,但当烧结态硬质合金再一次加热时,其钴结相中的钨含量要增加。所以淬火后高钴硬质合金的粘结相中的钨含量甚至比低钴硬质合金的粘结相中的还要高,这就是为什么钴粘结相由密度六方转变成面心立方的温度随硬质合金中钴含量的增加而提高。
This work confirmed that WC-Co cemented carbide can improve the flexural strength by heat treatment. The increased flexural strength is determined by the cobalt content in the alloy. The higher the cobalt content, the more the flexural strength increases. Mainly due to quenching heat treatment inhibited the high temperature stability of the face-centered cubic cobalt phase into a close-packed hexagonal cobalt phase. In this experiment, the phase transition temperature of the close-packed hexagonal cobalt phase into the face-centered cubic cobalt phase was also measured by the differential thermal analyzer in the heating process of the WC-Co alloy. It was found that the phase transition temperature increased with the increase of cobalt content in the alloy, such as YG8 is 742 ℃, YG15 is 770 ℃, YG20 is 821 ℃, which is due to high cobalt alloy binder phase in the heating process has a higher Tungsten content. In this experiment, it is also found that the content of low-cobalt cemented carbide after sintering is higher than that of high-cobalt cemented carbide because the sintering temperature of low-cobalt cemented carbide is usually higher than that of high-cobalt cemented carbide, In other words, the higher the sintering temperature, the higher the tungsten content in the binder phase. However, when the cemented carbide is once heated again, the tungsten content in the cobalt phase increases. Therefore, the content of tungsten in the binder phase of the high-cobalt cemented carbide after quenching is even higher than that in the binder phase of the low-cobalt cemented carbide, which is why the cobalt binder phase is transformed from a hexagonal density to a face-centered cubic temperature With the increase of cobalt content in cemented carbide.