Cemented carbide and process for producing same

Abstract

The present invention relates to a cemented carbide comprising WC grains, 3- 20 wt. % binder selected from Co or Co and Ni and grain growth inhibitors wherein the WC mean grain size lies in the range of 180 nm and 230 nm, at least 10+/-2 % WC grains are finer than 50 nm and 7+/-2% WC grains have a size from 50 to 100 nm. The invention further relates to a process for production the cemented carbide including the stages of milling WC powder with specific surface area (BET) of 3.0 m<2>/g or higher with binder and grain- growth inhibitors; pressing green parts; pre-sintering the green parts in H2 at 400 DEG C to 900 DEG C for 5 to 30 min; sintering in vacuum at temperatures of 1340 DEG C to 1410 DEG C for 3 min to 20 min; and HIP-sintering in Ar at pressures of 40 to 100 bar at temperatures of 1340 DEG C to 1410 DEG C for 1 to 20 min.

Description

technical field [0001] The present invention relates to cemented carbides comprising tungsten carbide (WC) grains having an average grain size of less than 0.3 microns, and methods of making the cemented carbides. Background technique [0002] The general trend in the cemented carbide industry is to produce WC-Co materials with the lowest possible average WC grain size, especially with grain sizes in the nanomaterial (grain size less than 0.1 micron or 100 nm) category. WC-Co cemented carbides prepared from WC powder with an average grain size of less than 0.3 microns, and WC-Co cemented carbides with an average grain size of WC close to 0.2 microns, are called "near-nano (near-nano) cemented carbides" or "near-nano" cemented carbides -Nano-hard alloys" (see such as M.Brieseck, I.Hünsche et al., "Optimi sed sintering and grain-growth inhibition of ultrafine and near-nano-hard alloys nano hardmetals). Proc. Int. Conf. PM2009, Copenhagen, EPMA). It has now been found that ne...

AI Technical Summary

Problems solved by technology

[0008] The third issue concerns the need for fine tuning of the carbon content in powdered WC-Co mixtures obtained from nano or near-nano powders

However, in the case of near-nanometer sintered carbides, it was found that even small additions of metal W or carbon black lead to microstructural defects such as Co (Co lakes) enriched fields and / or or irregular WC large grains

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