Preparation And Research Of Mo-based Interlayer For Diamond Deposition On The Cemented Carbide

Cemented carbide cutting tools with diamond have the advantages of high hardness, wear resistance of the diamond, and the characteristics of good toughness and excellent impact resistance of the cemented carbide substrate, becoming the most promising tool material. However, the existing of Co in cemented carbide can cause the dissolution of carbon, restrain the nucleation and growth of diamond, resulting in low adhesion of diamond coatings, which has restricted its wide application in the processing and manufacturing industries. The interlayer is synthesized on surface of the cemented carbide by double glow plasma surface alloying surface metallurgy technology. It is very high that the strength of metallurgical combination between the interlayer and the substrate, and it can hinder the diffusion of Co in the substrate, effectively enhanced the bonding strength of diamond coating. But in the high temperature preparation process of interlayer, η phase, which is loose brittle inter-metallic compound, is formed in the subsurface of the cemented carbide, reducing the strength of the substrate, seriously affect the mechanical properties. A certain amount of CH4 as a carbon source to avoid forming η phase in the interlayer, and high hardness of Mo2 C phase was generated due to the reaction of Mo with CH4 in the preparation process of Mo-based interlayer,improving the cutting performance and impact resistance of the tool.In this paper, Mo as a source material, a certain amount of CH4 as a carbon source in the Ar protection atmosphere, Mo-based interlayer was synthesized on surface of the cemented carbide by double glow plasma surface alloying surface metallurgy technology. By investigating the influence of CH4 concentration, substrate temperature, the voltage difference between the source electrode and the cathode on the surface morphology, phase composition and binding properties of the transition layer, optimizing the preparation process of the transition layer。 Subsequently, the diamond coatings were deposited on the surface of the optimized Mo-based interlayer by the TYUT type high-power MPCVD device. The main conclusions of the study:(1) With the increase of CH4 concentration, content of η phase transition layer gradually decreased till disappeared, the content of the Mo2 C and MoC increased gradually, but decreased the bonding strength.(2) In the low substrate temperature, interlayer was composed of nano-particles of the cellular structure, bonding strength was poor; with the increase of substrate temperature, the cellular structure merge combined until disappeared, the continuity, dense, smooth and bonding strength of the interlayer were improved; when the temperature was too high, binding strength was bad.(3)With potential difference increases, the surface morphology of the interlayer did not change, but Mo and Mo2 C relatively increased; when the potential difference was too low or too high, η phase would appear and binding strength of the interlayer was poor.(4)Deposited on the optimization of interlayer continuous and dense micron diamond coating; the diffusion of C elements leaded Mo in the interlayer to become Mo2 C, and so that part of the Mo2 C transformation for the MoC, while the interlayer completely blocked the outward diffusion of the Co binder phase, it is conducive to enhanced coating bonding strength.