CVD-diamond-coated tools

When the performance and price of CVD tools compare favorably with those of PCD tools, CVD tools may displace PCD tools in some applications. Woodworking tools represent another major market segment for diamond coatings. Tungsten carbide blades already comprise a large part of the woodworking tool market. CVD-diamond-coated tools have yet to be used in woodworking and, thus, they offer an excellent business opportunity. 

Several companies are engaged in the production of CVD-diamond-coated tool inserts. DeBeers, Mitsubishi, Nachi-Fujikoshi, Norton, Kennametal, Sandvik, and Sumitomo are the major firms. Kennametal and Sandvik provide diamond-coated tools on a commercial basis. Based on the input of several tool insert manufacturers, the estimated world market for diamond-coated inserts is 10 to 20 million per year. As discussed above, CVD- diamond-coated inserts are primarily targeted for machining... 

Fig. 14 Cutting performance of uncoated, PCD and CVD-diamond-coated tool inserts while milling graphite. ...

Other potential applications for CVD-diamond coatings include, woodworking tools. 

Thin-film diamond and diamond-Uke coatings are deposited on finish-groimd cemented carbide tools such as end-mills and drills. The main benefit of CVD diamond coatings is that there is no subsequent grinding or finishing operation on the tool necessary. 

Single crystals have to be bonded to a substrate in a separate operation and that, coupled with their high cost, limits their general use in tooling (see Ch. 12). CVD-diamond coatings may provide a cheaper solution once the adhesion probiem is solved satisfactorily. As mentioned in Sec. 4.5, poiycrystalline materials do not show the wear anisotropy characteristic of singie-crystai diamond and from that standpoint are better performers. 

Another approach is to coat the cutting tool material with a carbide former, such as titanium or siUcon or their respective carbides by CVD and deposit diamond on top of it. The carbide layer may serve as an iaterface between diamond and the cemented carbide, thus promoting good bonding. Yet another method to obtain adherent diamond coatings is laser-iaduced microwave CVD. By ablating the surface of the substrate with a laser (typically, ArF excimer laser) and coating this surface with diamond by microwave CVD, it is possible to improve the adhesion between the tool and the substrate. Partial success has been achieved ia this direction by many of these techniques. 

Figure 6.49 Examples of cutting and drilling tools coated with CVD diamond ( L. Schafer).

The world-wide interest in CVD diamond is in a considerable part due to its unsurpassed mechanical hardness and wear resistance, promising the ultimate wear protection for tools and machine parts to be achieved by direct coating from the gas phase. However, the exceptional position of diamond under natural... 

Substrate Materials. Cemented tungsten carbide (WQ is a major substrate cutting tool material. It has been successfully coated with CVD diamond with good adhesion especially with an intermediate carbide-former layer.l JI ... 

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