This layer is combined with the matrix metallurgically . for the wc particles of the layer, the coaser the wc particle is, the higher the radio is, and the worse the composite layer is . the optimum size of wc particles is about 70 ~ 150 mesh, and the optimum volume percentage of wc particles is about 25 ~ 40 % 复合层中的wc颗粒越粗化,所占比例越多,对复合层与母材结合越不利,试验得知wc的粒度为70~150目,体积分数为25~40%时,复合层结合良好。