Sunthesis Of Metal Interlayer Of Diamod-coated Cemented Carbide Cutting Tools By Double Golw Plasma Surface Alloying Technique

Cemented carbide cutting tools with diamond coating have high surface hardness and low friction coefficient and are therefore widely used in industry.. However, the existing of Co in cemented carbide would induce dissolution of carbon, restrain diamond nucleation and promote the formation of graphite during chemical vapor deposition (CVD), which can impair usability and adhesion of the coating.Acid-base two-step method for surface roughening and Co removing, or preparing of interlayer between coating and cemented carbide by CVD or PVD are often used to improve the adhesion of diamond coating. The disadvantages of these methods are:the former would weaken mechanical properties of substrate material, and bad adhesion between interlayer and substrate is always presented at the latter. It’s worth noting that the interlayer prepared by double glow plasma surface metallurgy technology has the potential to present satisfied adhesion to both of the diamond coating and cemented carbide. In this paper, interlayer were prepared on surface of cemented carbide by double glow plasma surface metallurgy technology and diamond coating were deposited thereafter using microwave plasma chemical vapor deposition (MPCVD). The microscopic morphology, phase composition and mechanical property were examined by scanning electron microscope (SEM), X-ray diffraction and Rockwell hardness tester.At first, three kind of metallic interlayer (Mo, W, Cr) were pepared under various holding time. The result indicated that these three metallic interlayers were metallurgically bonded with the substrate. However the Mo interlayer could prevent outward diffusion of Co and achieve preferable adhesion as well, exhibited superior structure and performance to the W and Cr interlayers. The adhesive strength of Mo interlayer can reach maximum adhesive strength at processing temperature of800℃～900℃. Then the preparing condition of Mo interlayer was further optimized by investigating the effects of voltage difference between source electrode and cathode as well as holding time, it was found that the increase in voltage difference and holding time could promote the growth of interlayer, but the adhesive strength showed downward trend. Finally, diamond coating were deposited on Mo interlayer prepared under the optimized condition, and the coatings formed with various deposition time were observed and characterized, The result showed that thediamond coating after deposition for4hours possessed high consistency and adhesive strength.The study of this paper presents a new approach to prepare interlayer for making cemented carbide tools with diamond coating, the interlayer prepared by double glow plasma surface alloying technology can guarantee the sufficient bonding to the substrate materials as well as the diamond out layer. The application of this new method would be a possible promotion to cutting tool industry.