硬质合金热处理和钴粘结相的转变温度

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。

Heat Treatment of WC-Co Hard Metals and Transformation Temperature of Cobalt Binder Phase

The present work has found that the transverse rupture strength of WC-Co hard metals can be improved by quenching heat treatment. The icrement of transverse rupture strength(TRS) is dependent on the cobalt content of hard metal.The higher the cobalt content of hard metal is,the more the increament of transverse rupture strength is. The main rea son is that the transformtion of face centered cubic cobalt stable at high temperature to hexagonal closepacked can be depressed by quenchin g heat treatment.The transformation temperature increases with the increase of cobalt content of hard metal by means of differential thermal anaysis because binder phase of high cobalt hard metal contains higher tungsten content than that of low hard metal during reheating.