Materials of diamond tools include single crystalline diamond (both natural and artificial, natural signal crystal diamond is expensive and is replaced by an artificial single crystal diamond), synthetic polycrystalline diamond (PCD) and synthetic polycrystalline diamond and cemented carbide composite blade (PCD / CC) and CVD diamond.
Single crystalline diamond
Single crystalline diamond used as cutters should be coarse grain size, (mass greater than 0.1g, minimum length not less than 3mm), mainly used for precision and ultra-precision machining which has strict requirement on geometry and dimensional accuracy.
Natural single crystal diamond exhibits the most wear-resistance. Fine texture of its own, after fine grinding, rounded cutting edge radius can be as small as 0.008 ~ 0.005μm. Natural single crystal diamond has multiple crystal orientations thus giving differing machining results, and contains impurities. Due to its demanding application condition, and the limited resource, higher price, PCD,PCD/CC and CVD diamond cutters are mostly used, while natural single crystal diamond cutters are mainly used in some ultra-precision machining non-ferrous metals or gold jewelry production.
The size, shape and properties of synthetic single crystal diamond has a good consistency. Due to increasingly developed high temperature and pressure technology, synthetic single crystal diamond can be manufactured. Especially in the processing of high wear layered laminated wood, its performance is better than PCD diamond, and does not cause edge passivation at an early stage.
Synthetic polycrystalline diamond (PCD) and synthetic polycrystalline diamond and carbide composite blade (PCD / CC)
PCD consists of small particles of diamond (on the order of micrometers to tens of micrometers) which are mixed with a binder, normally cobalt-based, at a high temperature (about 1800 ℃), high voltage (5 ~ 6MPa). Its hardness is inferior to single crystal diamond, but it has single crystal orientation, when used as a cutting tool, there is no requirements on sharpening, otherwise natural diamond must select the best of the cleavage plane as a rake. During cutting, it exhibits higher wear-resistance, and stands long time cutting.The polycrystalline diamond layer offers controlled wear and the retention of a sharp cutting edge. The service life is 10-500 times of WC tools, and due to the conductivity of metallic binder, PCD is easy to cut to shape, and rich source of raw materials, the price is just a hundredth to tenth of the WC tools, and it is a perfect substitute of WC tool.
In order to improve the toughness and weldability of PCD cutters, cemented carbide as base material,0.5 ~ 1mm PCD is sintered or pressed on its surface to make PCD / CC. PCD / CC can be welded or clamped to tool. Because of its good weldability, easy regrinding, low cost, it is widely used. Be noted, sharp edge and surface quality of PCD and PCD/CC are not as good as singlecrystal diamond tool, further more, its poor workability, the small grinding ratio, it is difficult to fabricate complex products including the indexable inserts with chip breakers and end mill.
CVD diamond is a pure diamond material of high abrasion resistance,free of binding agent, which is manufactured at low pressure (<0.1MPa). There are two main forms:CVD film coating (CD) and CVD thick (TFD).
CD is made from polycrystalline diamond by chemical vapor deposition process, VCD depositing
Because the base material can fabricated to complex shapes easily, it applies to geometrically complex tools, such as taps, drills, end mills and indexable blades with chipbreaker. There are many CD tools on the international market,CD1810 of Sandvik in Sweden,KCD25of Kennemetal in United States, mainly for non-ferrous metals and non-metallic materials, high-speed precision machining, service life is nearly 10 times or more than that of uncoated WC tools.
But CD tool is not suitable for machining metallic composite materials, because hard particles in composite materials will damage the coating in a very short time, so even though the price of CD tool is lower than the same PCD tools, however, due to poor adhesion between the diamond film and base material, its application is limited.