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采用合金粉末烧结体表面观察法研究了稀土在WC-Co硬质合金中的作用机理。合金中的稀土分别以混合稀土(以La和Ce为主体成分)-Co预合金粉(简称RE-Co预合金粉)形式和La(NO3)3的丙酮溶液形式在湿磨时直接加入。用扫描电镜和能谱仪对平均粒径小于200μm的2种球形稀土硬质合金粉末(简称合金粉末)烧结体表面进行观察与分析,发现:以RE-Co预合金粉形式加入稀土时,在烧结过程中,合金中的稀土La和Ce以及杂质元素在合金粉末烧结体表面产生了明显的富集,形成了含La,Ce,S,Ca,W,C和O的复杂形式的化合物,在稀土富集物中没有检测到Co。以La(NO3)3形式加入稀土,在合金粉末烧结体表面没有检测到La。说明在合金粉末烧结体表面不存在La的富集或聚集。稀土的添加形式同时也影响合金粉末烧结体表面硬质相WC与粘结相的比例,以RE-Co预合金粉末形式加入稀土,合金粉末烧结体表面粘结相含量较少,因此,稀土的添加形式影响其在硬质合金中的作用机理。以RBCo预合金粉形式加入稀土,合金中的稀土不但具有较好的富集合金中杂质元素的作用,而且还可以阻止烧结体表面富粘结相结构的形成。
The effect mechanism of rare earth in WC-Co cemented carbide was studied by surface observation of alloy powder sintered body. The rare earths in the alloy are respectively added in the form of mixed rare earth (La and Ce as main components) -Co pre-alloyed powder (RE-Co pre-alloyed powder) and La (NO3) 3 as acetone solution in wet grinding. Scanning electron microscopy and energy dispersive spectroscopy were used to observe and analyze the surface of two types of spherical rare-earth cemented carbide powders (alloy powders) with average particle size less than 200μm. The results showed that when rare earths were added in the form of RE-Co pre-alloyed powders, In the sintering process, rare earth elements La and Ce in the alloy and the impurity elements are obviously enriched on the surface of the alloy powder sintered body to form the complex forms of compounds containing La, Ce, S, Ca, W, C and O Co is not detected in rare earth enrichment. La was added as La (NO3) 3, and La was not detected on the surface of the alloy powder sintered body. Indicating that there is no enrichment or aggregation of La on the surface of the sintered alloy powder. The addition form of rare earth also affects the ratio of hard phase WC to binder phase on the surface of the alloy powder sintered body. The rare earth is added in the form of RE-Co pre-alloyed powder, and the content of binder phase on the surface of the alloy powder sintered body is small. Therefore, The added form affects its mechanism in cemented carbide. RBCo pre-alloyed powder added to the form of rare earth, alloy rare earth not only better enrich the role of the alloy elements, but also can prevent the sintered body surface rich binder phase structure formation.