Study On Process Of WC-MgO Compound Material By Pressureless Sintering

Cemented carbides have the advantages of high elasticity modulus, high hardness and strength, high red hardness, high abrasive resistance, and low thermal expansivity, so they are widely used in a number of fields, such as machining operation, mine exploitation, military project, chemical industry, metallurgy. The main binder of tradition cemented carbide (WC-Co) is cobalt, which is increasingly expensive as the reserve is quite low. Above is the reason that we should find an alternative material of cobalt to compose a new kind of cemented carbide with high hardness and toughness. In recent years, Donghua University has developed a series of research works on manufacturing WC-MgO composite material by hot pressed sintering, and has got good results on many fields, such as powder process, composition proportion, sintering process and so on.Currently, the sintering process of WC-MgO composite material is mainly hot pressed sintering, which is widely used in powder metallurgy. With the shortage of low production efficiency, hot pressed sintering is hard to manufacture by mass production. So it is necessary to start the research of composing WC-MgO composite material by pressureless sintering and try to apply the sintering process of hot pressed sintering into pressureless sintering process, which would be count for the practical applications.The study mainly includes:1. The influence of different pressures in producing WC-MgO blanks.The WC-MgO composite powders were synthesized by high-energy ball milling method from WC and MgO powders. And then pressed the composite powders into blanks by different pressures. In the end, sintered the blanks by pressureless sintering process. A detailed research was carried out into the influence of pressure works on the mechanical properties of the WC-MgO bulk.2. The influence of infinitesimal cobalt on pressureless sintered WC-MgO composite material.The WC-MgO composite powders were synthesized by high-energy ball milling method from WC, MgO and Co powders. Pressed the composite powders into blanks by isostatic cool pressing. And then sintered the blanks by pressureless sintering process. Tested the phase, Vickers hardness and the fracture toughness of WC-MgO composite material, and then analysed the influence of infinitesimal cobalt on pressureless sintered WC-MgO composite material.3. Effects of La2O3on pressureless sintered WC-MgO composite material.The WC-MgO composite powders were synthesized by high-energy ball milling method from WC and MgO powders. And then the powders were pressed into blanks by isostatic cool pressing. At last, the powders were presureless sintered. A detailed research was carried out into the influence of rare earth oxide (La2O3) contents on the microstructure and mechanical properties of the WC-MgO bulk. The effective mechanisms of rare earth (La2O3) in pressureless sintered composite were also discussed.