Frequently Asked Questions

What are the critical factors for the success of the diamond coating? What is important to know for r-BeSt coating and the user respectively?
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• Composition of the tungsten carbide: Declaration of the tungsten carbide producer and the tungsten carbide grade as well as declaration of the WC/CO/mixed carbide content and the grain size.
• Declaration of the application material and the processing
• Declaration of the desired coating length
• Tool’s suitability for coating: If the tool is soldered, the solder has to bare coating temperatures of at least 750°C. A technical clarification has to be undertaken in advance.
  The tool shows coolant bores? In case these coolant bores contain rests of sinter or dirt, vaporisation might occur which will have negative effects on the coating result.
  Is the tool’s geometry suitable for coating? Certain geometries require a technical clarification before coating process starts. If tolerances have to be kept, a technical clarification (with a drawing) should be undertaken in advance.
  
• Packaging: The tools should be sent to r-BeSt coating in their original packaging, covered with bubble wrap in a suitable cardbordbox solely in order to avoid damage during transportation.
  

Why does r-BeSt coating need the exact specification of the tungsten carbide?
[Answer] The binder, contained in the tungsten carbide (generally cobalt or nickel) hinders the growth of pure diamond and transforms the deposited diamond into the graphite phase respectively. Therefore it is necessary to remove these elements from the tool’s zone which is close to the surface. This depletion layer is different for each tungsten carbide, depending on the composition. In order to guarantee an optimal diamond coating, the cobalt-free zone should be neither to large (in order not to make the tungsten carbide brittle) nor to small (in order not to interfere with the diamond growth). Therefore the exact amount of all elements (especially cobalt) must be known. Due to many years of development, r-BeSt coating is even able to coat tungsten carbide grades with a high cobalt content (up to 20%) as standard and therefore stands out from the competitors.
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What are the main differences between r-BeSt diamond coatings and the CVD-coatings of the competitors?
[Answer] The main difference is the nanocrystallintiy of the r-BeSt diamond coating. Due to the smallness of the diamond crystals an outstanding adhesion (even on ultrafine tungsten carbide grades), extreme smoothness and sharp edges are given.
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What are the main differences between r-BeSt diamond coatings and DLC-coatings?
[Answer] DLC („Diamond-like-carbon“)-coatings contain carbon which is sp²-hybridized, which means that parts of graphite or amorphous carbon are contained. Depending on the type there are only some parts of the carbon crystalline, the rest amorphous, making the DLC-coatings softer than the r-BeSt diamond coatings that consist of 100% sp³-hybridized carbon and are therefore less suitable for wear machining.
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Which materials can be coated?
[Answer] The latest list of recommended tungsten carbides for coating can be found here. Tungsten carbide grades that are not on that list and unknown to r-BeSt coating, have to undergo an optimization before the normal coating process is started. During this process the suitability of the tungsten carbide grade for diamond coating is tested and the optimal alternative for pre-treatment developed. A clarification with r-BeSt coating is necessary.
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Which are the criteria for the existing tungsten carbide list? Why is the list subject to constant change?
[Answer] In this list you find all those tungsten carbide grades, which are constantly diamond coated in large amounts at r-BeSt coating and which have proven to be the BeSt during application at our customers. Once a month the list is updated, the latest frequency scale of tungsten carbide grades is incorporated. This means that a carbide grade which was so far included in the list might drop out if there were no tools for diamond coating in the corresponding month. Of course these tungsten carbide grades remain perfectly suitable for diamond coating. If you can’t find „your“ tungsten carbide on this list, please do not hesitate to contact us! We offer expertise in the diamond coating of more than 100 tungsten carbide grades and are pleased to offer our advice!
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Is it possible to re-coat a used and re-grinded tool?
[Answer] In general, the coating of re-grinded tools is possible. However, the optimal adhesion of the coating can only be guaranteed for those areas that are 100% free of previous coatings.
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Is it possible to remove the r-BeSt diamond coating entirely from the tool?
[Answer] A complete de-coating, without damaging the tungsten carbide structure of the tool, is not possible at the moment, due to the perfect adhesion of the r-BeSt diamond coating.
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Which layer thickness is normally deposited?
[Answer] The standard layer thickness of the r-BeSt diamond coating averages at 5µm, depending on the tools’ diameter. Due to the nanocrystalline structure – the single diamond crystals show a size of a few nanometers (=0,000001mm) – the layer is an enclosed unit at a thickness of approximately 100nm. At an order volume, that completely fills one coating facility, the layer thickness can be adjusted with a precision of +/- 10%. According to customer’s wishes custom-made layers can be produced with other thickness than normal.
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What is the value of the r-BeSt diamond coating for the coefficient of friction?
[Answer] The coefficient of friction of the r-BeSt diamond coating was measured at an bearing application, the measured values under-run the coefficient of friction of Teflon by app. 10%. Coefficient of friction is herby defined as the ratio of two forces. The force, necessary to move one body against another one, is related to the force, that presses this body against the mat. The value for Teflon is 0,04 (non-dimensional figure).
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How are the prices calculated at r-BeSt coating?
[Answer] The relevant data for price-calculation is the area in the coating facility that is occupied by a tool. For rotating tools this is the largest diameter. A mill with a cutting diameter of 3mm and a shank diameter of 6mm is therefore calculated with the price for diameter 6mm. Besides the coating prices are also depending on the coating length, therefore the coating length has to be indicated with each order. Please notice that the total length of the tool is NOT relevant for the coating price.
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Which coating capacity is at disposal at r-BeSt coating?
[Answer] Due to close partnership with our customers and by constant market-monitoring enough capacity is held out constantly, in order to reliably meet our standard delivery time (15 working days), even at an extreme increase of order volume.
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How was the company name created?
[Answer] The company name combines the shortnames of the four persons that took part in the development of the technology (ROsina, BErtel, STeinmüller). Besides the Greek letter “r“, as the symbol for density, stands for one of the outstanding properties of diamond.
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