PVD or CVD? How to better understand coating selection and application?
PVD and CVD are commonly used in surface treatment of tools and molds at present. CVD is based on chemical vapor deposition, while PVD is based on physical vapor deposition. Due to their differences in principle, they have different final coating results and different emphases in application.
Compared with CVD, PVD is thinner. The coating thickness of CVD is 10~20 m, while that of PVD is only about 3~5 m. PVD processing temperature probably at about 500 ℃, and CVD in furnace temperature at 800 ~ 1000 ℃. Therefore, it can be seen that CVD requires high temperature resistance of the materials to be processed precisely because of the high temperature. We can hardly see other materials except cemented carbides on the tools processed by CVD, because only cemented carbides can withstand such a high temperature in the mainstream cutting materials.
In addition, the CVD coating, due to its thicker thickness and higher treatment temperature, is prone to generate tensile stress on the surface during cooling, thus forming subtle cracks. These cracks in the case of external impact (such as: milling) easy to expand, once expanded throughout the coating will occur when the coating peeling, so that the tool matrix coating loss of protection. Therefore, CVD coated tools are widely used in turning blades. Since the cutting force sustained during the whole cutting process is uniform and continuous, the wear resistance of CVD coating due to its thickness will be obvious.
In contrast, intermittent cutting represented by milling. In the process of cutting, the cutting edge of the continuous cutting impact coating and tool surface. PVD lower processing temperature (500 ℃), so that it will form the compressive stress in the process of cooling rather than tensile stress, thus produce the result that prevent cracks generated and extension. In addition, due to the thin PVD coating thickness, the geometric shape of the blade does not change much, which can retain the sharpness of the blade to a large extent and reduce the generation of cutting force and cutting heat. To sum up, it can be seen that PVD is more suitable for the interrupted milling process as well as almost all of the overall type of cutter.
In view of the different convenience brought to customers by PVD and CVD coating, IKS PVD,offer PVD coating machine and CVD coating machine, then, customers will be able to more timely and convenient experience to provide its ultra-cost-effective coating services.
To be fair, compared with PVD, CVD has another advantage that is difficult to catch up with the current common PVD technology, that is, the most commonly used CVD coating material - aluminum oxide (Al2O3). Aluminum trioxide has very good physical and chemical stability, hard wear resistance and low cost, but it is difficult to be achieved on ordinary PVD due to the constraints of the production process. Of course, due to the many advantages of PVD in other aspects, and due to its continuous expansion in coating materials in recent years, its performance has been gradually better than CVD in more and more aspects. Its current share in the world knife market from more than a decade ago 20%~30% gradually increased to more than 50% now.
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