Introduction of Cermets Cutting Tools
1)With the continuous development of the ceramic cutting tools’s composition structure and pressing technique,especially with the progress in nanometer technology ,it becomes to be possible to increase toughness for the ceramic materials. In the coming future ,ceramic will bring the third cutting machining revolution after high speed steel and tungsten carbide .The ceramic cutting tools with high hardness(HRA91~95),high T.R.S (750~1000MPa),good wear-resistance ,stable chemical,good anti-adhesion ,low friction-coefficient and cheap price etc characters.Besides that ,the ceramic cutting tools also have very good high-temperature hardness ,even in 1200°C,its hardness is still at HRA80.
2)Under normal cutting condition,the ceramic cutting tools have very long service life ,meanwhile its cutting speed is 2~5 times than tungsten carbide ,particularly for machining high hardness materials with finish and high speed machining ,it is available to machine the workpiece with hardness reaching HRC65 such as various hardened steels and cast irons.The common using ceramic includes Al2O3-base ceramic ,SiN-Base ceramic ,cermets and whisker reinforced ceramic .
3)The red hardness of Al2O3-Base ceramic cutting tools is better than tungsten carbide,meanwhile its cutting edge would not be plastic-deformed in high speed cutting condition ,but it has very low toughness and T.R.S .In order to improve its toughness and increase the anti-impact strength ,usually the mixed material of ZrO and TiN is added ,of course the another way to do that is to add pure metal or SiN whisker .On the other hand ,the SiN-base ceramic has very good toughness besides good red hardness ,comparing to Al2O3-Base one ,its disadvantage that it is very easy to be diffused in high temperature when machine steel ,and worsen wear of cutting tools.Thus the SiN-base ceramic is mainly used to intermittent turning gray cast iron and milling gray cast iron.
4)Cermets is a material with carbide as base,in which TiC is taken as the main content of hard phase (0.5~2um),they are fused with binder of Co or Ti ,which are a similar material as tungsten carbide,but have comparatively low affinity,good friction coefficient and wear-resistance .Comparing with tungsten carbide ,it is capable to bear higher cutting temperature ,but lack of tungsten carbide’s anti-impact performance ,toughness in heavy-cutting,and strength under low speed but big feed condition.After a lot of studies in recent years ,the cermets’ transverse rupture strength is improved a lot by means of upgrading and taking new processing technique ,such as the new cermets NX2525 developed by Mitsubishi and CT series and coating cermets series inserts developed by Sandvick,their grain sizes are under 1um ,meanwhile the T.R.S and wear-resistance are much higher than the common cermets ,so significantly broaden the scope of application
