Self-Lubrication of Machining Tools in Dry via In-situ Formed Tribofilms
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0890-Y01-01.1
Self-Lubrication of Machining Tools in Dry via In-situ Formed Tribofilms Tatsuhiko Aizawa, Shigeo Yamamoto1 and Taro Sumitomo1 Department of Materials Science and Engineering, University of Toronto Room 140, 184 College Street, Toronto, Ontario, Canada M5S 3E4 Japan Office: 1-24-12 Shinkawa, Chuo-ku, Tokyo 104-0033, Japan 1 Research Center for Advanced Science and Technology 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan ABSTRACT Green manufacturing technology has become a significant innovative keyword to reduce the environmental burden and CO2 emission at the stage of manufacturing and production. In daily operations by machining, huge amount of lubricating oils and cleansing agents is wasted so that dry machining technology provides us a way to completely reduce these wastes. Among several candidates, self-lubrication via in-situ formation of lubricious oxide films is accommodated to protective coatings in order to attain low friction and wear state even at higher cutting speed range. Materials science of in-situ formed lubricious oxide tribofilms is stated with consideration of accommodation mechanism via the chlorine implantation. Mechanical characterization is made for evaluation on elasto-plastic deformation of lubricious oxides. Turning test is employed to evaluate dry machinability of various tools for wide range of cutting speed. Self-lubrication in dry machining is described both for bare WC and TiCN-coated WC tools with and without chlorine implantation. Precise microstructure analyses are made by using the laser microscope, EDS and XPS. In-situ formation of lubricous oxides proves that self-lubrication process takes place even in dry machining to reduce the flank wear and friction coefficient.
INTRODUCTION Green manufacturing has become a key technology toward significant reduction of environmental burden and CO2 emission in industrial production [1]. In daily operation by machining and forming, huge amount of lubricating oils and cleansing agents are wasted so that dry machining and dry forming are an important goal in the green manufacturing. At the absence of lubricants, tool/die – work material system suffers from high flash temperature on the solid-solid contact surfaces. Increase of flash temperature, leads to severe adhesive wear, where adhesive metallic constituents from work materials are oxidized and these oxides cause high friction and high wearing state [2]. Dry machining and dry forming cannot be accommodated to practical operation without self-lubrication by tribocoating between tools and work materials. There are three tribocoating methods for self-lubrication to be working in dry as listed in Table 1. Hard coatings like DLC (Diamond-Like Carbon), c-BN or CVD-diamonds are effective to preserve low friction and wear state until the flash temperature is less than the critical value [3]. In-situ solid lubrication works well in the dry wear condition by embedded MoS2 and WS2 until the protective coating is completely diminished [4]. Under severe wearing conditions, these two t
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