Preparation, properties and microstructure of high hardness WC-Co cemented carbide tool materials for ultra-precision machining

WC-Co cemented carbides, with low binder content (Co content < 4 wt.%), have become prospects as ultraprecision cutting tool materials as a result of their high hardness, which can be ground to a sharp cutting edge when machining tools. In this paper, three cemented carbides, with Co content of 1 wt.%, 2 wt.% and 3 wt. %, were systematically investigated. The mode of preparation, properties, microstructure and ultra-precision turning of these cemented carbides were studied. It has been researched that 0.1 wt.% VC could effectively refine the WC grains to exhibit excellent properties. The optimum sintering temperatures for WC-1Co-VC, WC2Co-VC and WC-3Co-VC were 1350, 1300 and 1300.C, respectively. The resultant cemented carbides displayed extremely high hardness (2450, 2377 and 2325 kg/mm(2)), high relative density (> 99%), specific fracture toughness (8.89, 9.01 and 10.17 MPa center dot m(1/2)) and transverse rupture strength (1274, 1387 and 1474 MPa). During oxidation, from room temperature to 400. C, there was a slight reduction in the strength of the cemented carbides with no oxide formed. From 400 to 600. C, their strength decreased significantly with apparent oxides formed on the surface. At 800.C, all the cemented carbides experienced a severe drop in strength and massive oxidation on the surface and fracture surface. The cemented carbides were used to make cutting tools used for ultra-precision turning of brass. The surface roughness after machining with the three modified cemented carbide tools, with increasing Co content, were 22, 14 and 17 nm, respectively.

Automated summary

This paper investigates the preparation, properties, and microstructure of WC-Co cemented carbides with low binder content. The addition of a small amount of VC effectively refines the WC grains and enhances the performance of the cemented carbides. The cemented carbides prepared at different sintering temperatures show high hardness, high relative density, good fracture toughness, and transverse rupture strength. The strength and oxidation behavior of the cemented carbides are affected by temperature during the oxidation process. The cemented carbides exhibit different surface roughness when used for ultra-precision turning of brass, depending on the Co content.