Study On Influence Of Cutting Fluid On Cobalt Leaching From Cemented Carbide Tools

The cemented carbide tool is commonly used in machining. In cutting process, some cutting fluid can make cobalt leach from the surface of cemented carbide, which accelerates tool wear. With scanning electronic microscope and energy spectrometer etc., soaking test, friction test and abrasion test are adopted to study the influence of cutting fluid additives on cobalt leaching from cemented carbide, and the inhibitors for cobalt leaching are chosen. Adding the inhibitors to cutting fluid can efficiently inhibit cobalt leach, thus can relieve the wear of cemented carbide tool, lengthen the cutting life and reduce machining cost.The influence of main ingredients of cutting fluid on cobalt leaching from cemented carbide was studied. The results show that Triethanolamine and tri-Sodium phosphate can make cobalt leach from the surface of cemented carbide. The mechanism of cobalt leaching is that Triethanolamine and cobalt form complex compound, and the complex compound is dissolved in water so that it can make cobalt leach. Disodium hydrogen phosphate, which is the hydrolysis product of tri-sodium phosphate, forms deposition with cobalt to make cobalt leach. Benzotriazole, oleic acid, sodium nitrite, sodium carbonate anhydrous, borax and composite boric acid ester all have inhibited effects on cobalt leaching of surface of cemented carbide tool. Benzotrizole and cobalt produce a complex compound that covers on the surface of cemented carbide in form of film. This film can protect base metal not to lead cobalt leaching. Oleic acid as lubricant may form triethanolamine oleate with triethanolamine, and triethanolamine oleate attaches on the surface of cemented carbide to inhibit cobalt leaching. Sodium nitrite, sodium carbonate, borax all prevent cobalt from leaching, which is obtained by the inhibition of cathode reaction or anode reaction. Adding benzotriazole into triethanolamine oleate solution can reduce cobalt leaching rate to a great degree. The inhibited effect of mixture of benzotriazole, triethanolamine oleate and borax is superior to that of mixture of benzotriazole and triethanolamine, and mixture of borax and triethnolamine oleate as well. Composite boric acid ester produced by oleic acid, triethanolamine and borax can also inhibit cobalt leaching, moreover it produces a better inhibition for cobalt leaching of cemented carbide if combined with benzotriazole. Preparation of cutting fluid with additives which have inhition for cobalt leaching of cemented carbide can efficiently prevent cobalt leach from cemented carbide tool, lengthen the tool life and lessen the harm to environment and human being as well.