The Trend of Cemented Carbide Materials with High Performance
1)Tungsten carbide with TaC and NbC added
After added the TaC and NbC ,the normal-temperature hardness,high-temperature hardness and high-tmeprature toughness of tungsten carbide are improved ,meanwhile ,they are also helpful to refine grain size, improve proliferation resistance and anti-oxidant capability ,meanwhile also increase its anti plastic-deformation strength.The TaC and NbC are formed into(W,Ta,Nb)C solid-solution with chemical stability higher than WC and TiC.In the new grades of type P,M and K tungsten carbide materials ,most of them are added TaC and NbC.
2)Fine and Ultrafine Grain-Size Tungsten Carbide
The hardness and wear-resistance of tungsten carbide are improved after refinement of the grain-size ,meanwhile ,the T.R.S is risen by means of appropriately increase of cobalt content.The average grain-size for common grade carbide cutting tools is 2~3um ,and the fine one is 1~2um,sub-micron one is 0.5~1um,but the ultrafine grain-size is under 0.5um .At first ,the find and ultra fine grains size are for Type K tungsten carbide ,however ,in recent years ,the type P and M tungsten carbide have been developed to this direction too.
3)Tungsten carbide with rare-earth elements added
The toughness,T.RS and wear-resistance are improved effectively by adding a small amount of cerium ,yttrium etc rare-earth elements,since they strengthen the hard and binder phase ,purify the grain boundary and improve the wettability of carbide solid-solution for the binder phase.This kind of grades are suitable for the carbide inserts with rough or semi-finish machining ,meanwhile they also have broad prospects in mining tools, diamond-hammer and drawing dies etc fields .Our country is very abundant in rare-earth resource ,so we are head in researching for this field.Type P,M,and K tungsten carbide were developed the new grades with the rare-earth elements added .
4)Tungsten carbide with coatings
The coatings as TiC,TiN,Ti(C,N),Al2O3 etc are coated onto the tungsten carbide substrate by means of CVD of PVD.The uncoated tungsten carbide mechanical and physical properties are the comprehensive performance of hard phase and binder phase ,so its hardness and wear-resistance is lower than the hard phase’ itself .On the contrary ,the surface hardness and wear-resistance of coated tungsten carbide are totally reflected the coatings’ actual performance ,so it is capable to improve the cutting tools’ service life and working efficiency ,decrease cutting force and optimize the surface quality .The coated cutting tools have developed greatly in the recent 20 years ,which take 50%~60% market of CNC cutting inserts.The substrate is still tungsten carbide with high toughness ,meanwhile ,with the different substrates ,this kind of coatings are available for type P,M and K tungsten carbide ,and there are very large application scope .
