Re Strengthening of Cemented Carbide by Lanthanide Rare Earth

Tungsten cobalt cemented carbide has been widely used as cutting tool and die material because of its high hardness and high wear resistance. By reducing the size of WC grain in the alloy to the ultrafine crystal grade (1um ~ 300nm), the strength and wear resistance of WC/Co system cemented carbide can be greatly improved.

However, in the traditional liquid phase non pressure sintering process, the ultrafine tungsten carbide particles are prone to abnormal growth. How to control the growth of WC has become one of the key technologies for the preparation of superfine crystal WC/Co cemented carbide.

In order to inhibit the growth of WC particles, special sintering methods, such as thermal isostatic pressure, plasma sintering, microwave sintering, etc., can be used. External force and auxiliary field can be used to suppress the growth of WC particles. However, these methods have the disadvantages of complex production process and high cost, which can not achieve industrial production. Another way to control the growth of ultrafine WC particles is by adding grain inhibitors, such as vanadium carbide VC, niobium carbide NbC and chromium carbide Cr2C3, but there is also a phenomenon of abnormal grain growth, and the grain size distribution of WC is uneven.

In order to overcome the shortcomings and defects of the existing ultrafine grained WC/Co cemented carbide technology, Xiao Daihong and others put forward a solution with reasonable group allocation and simple production process. By adding 0.1 ~ 2% rare earth lanthanum, the WC grain size and hardness and fracture toughness of the alloy can be effectively reduced, so that the alloy's performance is better than that of the existing ultrafine grained WC/Co cemented carbide.

Compared with the existing technology, the lanthanum doping method can improve the bonding performance between ultrafine grained WC/Co composite powder particles without changing the traditional ultrafine grained WC/Co cemented carbide preparation process and equipment.

Compared with the existing technology, the lanthanum doping method can improve the bonding performance between ultrafine grained WC/Co composite powder particles without changing the traditional ultrafine grained WC/Co cemented carbide preparation process and equipment, reduce friction powder compacts in the process, to improve the performance of the final forming, and then improve the density of the sintered alloy. At the same time, during the sintering process, lanthanum and rare earth elements are decomposed, forming tungsten cobalt boron compounds and rare earth borate compounds, which purify the grain boundary of WC particles and reduce the dissolution and precipitation of WC in Co. Finally, the size of WC grain in the sintered alloy is reduced, so that the ultra-fine grained WC/Co cemented carbide with excellent comprehensive properties is obtained, and the total properties of cemented carbide are high, which can meet the requirements of actual industrial production.

• < Prev
• Next >