WCA March 2015

5 Conclusions Nanocrystalline diamond composite coatings are deposited on the interior surfaces of tungsten carbide (YG6) drawing dies using HFCVD processes. According to the analysis results of SEM and Raman spectroscopy, nanocrystalline diamond coatings also contain a useful large percentage of multi-crystalline diamond structures with very small grain sizes of about 50nm and a large number of grain boundaries. These coatings provide very good wear resistance, high finish and low friction with aluminium. The application of nano-dies in the aluminium wire or tube (coaxial cable or aluminium-plastics compound pipe) drawing process can not only increase the working life of drawing dies dramatically (10~25 times of TC dies), largely reduce change-over time and increase productivity, but also ensure fundamental consistency of wire diameter and improve the quality and finish of drawing products, saving significant amounts of raw material. Additionally, nano-dies are highly adaptable to high-speed wire drawing. In particular, a water lubricating system can be adopted to replace the conventional oil-based lubricating system when using nano-dies for producing aluminium coaxial cable, aluminium-plastic compound pipe and aluminium wire, providing immediate economic benefits, reducing environmental pollution and implementing a green manufacturing process. 6 References [1] Dieler M Gruen, ‘Nanocrystalline diamond films’, Annu Rev Mater Sci 1999, 29: 211~259 [2] Sun Fanghong, Zhang Zhiming, Guo Songshou, Shen Hesheng et al, ‘Industrialisation of CVD Diamond Films: Diamond coated drawing dies and cutting tools,’ Bilateral Chinese-Russian scientific seminar (Hangzhou), 27 th -29 th December 2010 [3] Zhang Zhiming, He Xianchang, Shen Hesheng, Sun Fanghong, et al, ‘Pre-treatment for diamond coatings on free-shape WC-Co tools,’ Diamond and Related Materials, 2000, 9:1749~1752 [4] Zhang Zhiming, He Xianchang, Shen Hesheng, Sun Fanghong, et al, ‘Fabrication and application of chemical vapour deposition diamond-coated drawing dies,’ Diamond and Related Materials, 2001,10:33~38 [5] Li Zhenquan, Zhou Yan, Liu Yang, et al, ‘Application of nanocrystalline diamond composite coating compacting dies,’ Electric Wire & Cable (Chinese), 2005, 2:46~48 [6] Guo Songshou, Zhang Zhiming, Shen Hesheng, Sun Fanghong, et al, ‘Characterisation and Application of Nanocrystalline Diamond-coated Welding and Drawing Dies,’ Optical Fiber & Electric Cable (Chinese), 2007, 1: 9~12

consistency of wire diameter, saving raw metal material up to 1~2%. Additionally, nano-dies are welcomed in high-speed wire drawing and they are highly applicable to environmentally friendly ‘non-pickling’ wire drawing processes. 4.2 Water lubricating application perspective in Al wire and coaxial cable/Al-plastics compound pipe drawing process with nano-dies There is another dominant advantage of nano-dies studied in this paper. That is the change of lubricating method with a most attractive green element in addition to direct cost savings. Most production lines with TC dies use oil-based lubricants to cool the dies and decrease the friction in the reduction and bearing zones of the die. Another consideration is the finish of aluminium products. TC dies need an oil-based lubricant in order to achieve a satisfactory surface finish. However, oil-based lubricating systems also bring lots of concerns. For example, the cost of lubricants is high, expensive accessory equipment is required, and there is consumption of oil resources (in oil-based lubricant manufacturing processes). Additionally, oil-based lubricants carry pollutants into the workshop (smog, chemical particles and microbes) and there are great difficulties in recycling aluminium scraps. For drawing customers, the latter two factors are big problems, especially aluminium scrap recycling. A kind of water-based lubricating system can be successfully introduced to replace the conventional oil-based lubricating system when using nano-dies for producing coaxial cable and Al-plastics compound pipe. This is becoming very popular in Chinese production in recent years [5][6] . Success is the direct result of the unique structure of sp 2 -bonded carbon in the layer of nano-crystalline diamond coating of nano-dies. It brings not only very low friction in the interface with aluminium (and with good self-lubricating, similar to some graphite-like structures), but also better wetting with lubricating film in water-based lubricants (vs conventional multi-crystalline coating). Conventional TC dies will also meet difficulties of strong oxide etching and adhesive wear (to form abrasive dust etc) when using water-based systems. By contrast, the process is completely worry-free when using nano-dies because of the high degree of chemical inertness and very low wear rate of diamond coatings. Figure 5 shows the water lubricating application in the Al-plastics compound pipe drawing process with nano-dies at a customer’s plant in Zhejiang Province of China and the final appearance of the aluminium product. Used in this manner, the customer saves a large amount of cost of lubricating oil, accessory thermostat cleaning equipment and other processes, and significantly reduces environmental pollution. The Al-plastics compound pipes they produce are more consistent, have a more accurate diameter and a better finish than anything previously achieved using TC dies and an oil-based lubricating system. The same story has been repeated in multiple aluminium wire drawing applications in China. Nano-dies are welcomed by big manufacturers in China for the green element of water lubricating.

Shanghai Jiaoyou Diamond Coating Co Ltd 951 Jianchuan Road Shanghai 200240 China Tel : +86 215 473 0743 Email : judiamond@hotmail.com Website : www.judiamond.com Shanghai Jiaotong University 800 Dongchuan Road Shanghai 200240 China Tel : +86 215 474 0000 Website : www.sjtu.edu.cn

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Wire & Cable ASIA – March/April 2015