Research On The Interface Bonding Properties Of CBN Coated Carbide Tools

The cBN coated carbide tools have high hardness,wear resistance,good impact resistance and toughness,they are ideal tools for machining ferrous materials.At present,the research on cBN coated carbide tools at home and abroad is mainly concentrated on experimental research,and there is little research on the interface bonding properties from the perspective of microscopic atoms.Based on the first-principles and molecular dynamics methods,the interface bonding properties of cBN coated WC-Co carbide tools were simulated from the perspective of microscopic atoms.This research has important theoretical and practical significance for revealing the interface bonding mechanism of the coated tools and optimizing the coating preparation process.The interface bonding properties of cBN coated WC-Co carbide tools with different terminals were studied.Six interface models,WC-Co/cBN4B,WC-Co/cBN4N,WC-Co/cBN1B-Ox,WC-Co/cBN1N-OX,WC-Co/cBN1N-OY and WC-Co/cBN1B-OY,were constructed to calculate the interface adhesion works and fracture toughness.The research results show that:the WC-Co/cBN4B interface model is the most stable interface,which has a maximum adhesion work of 9.705 J/m2;the WC-Co/cBN4N interface model is the most unstable,which has a minimum adhesion work of 4.470 J/m2.Further analysis of the electronic structures such as charge density difference,density of state and Mulliken population of WC-Co/cBN4B and WC-Co/cBN4N interface models,show that compared with Co-N bond,the population number of Co-B bond is larger,the bond length is smaller,the bond energy is larger,and the Co-B covalent bond at the interface is stronger than the Co-N covalent bond.Based on the most stable and unstable interface models,the interface bonding properties of cBN coated WC-Co carbide tools with different interlayers were studied.Firstly,the interface bonding properties of the coated tools with Diamond single interlayer were studied.Two interface models,WC-Co/Diamond/cBN4B and WC-Co/Diamond/cBN4N,were constructed to calculate the interface adhesion works,fracture toughness and analyze the electronic structure.The research results show that:the adhesion work at the Diamond/cBN interface,and the interface bonding properties improved,while the adhesion work at the WC-Co/Diamond interface,and the interface bonding properties decreased;In these two interface models,the C-B bond and Co-C bond at the WC-Co/Diamond/cBN4B interface have larger population,smaller bond length,larger bond energy and stronger interface bonding propertie.Then,the interface bonding properties of the coated tools with SiC/Diamond double interlayers were studied.Four interface models,WC-Co/SiCc-Si/Diamond/cBN4B,WC-Co/SiCsi-C/Diamond/cBN4B,WC-Co/-SiCC-Si/Diamond/cBN4N and WC-Co/SiCSi-C/Diamond/cBN4N were constructed to calculate the adhesion works,fracture toughness of the interface and analyze the electronic structure.The research results show that the bonding properties of WC-Co/SiC interface is better than that of WC-Co/Diamond interface with single interlayer;Among the four interface models,the WC-Co/SiCsi-C/Diamond/cBN4B interface model has the largest interface adhesion work and the strongest interface bonding properties.Compared with the single interlayer rmodels:the model with the double interlayers has larger adhesion work,stronger interface bonding propertie,and more stable interface.The effect of deposition temperature on the interface bonding properties of cBN coated WC-Co carbide tools without interlayer,with single and double interlayers were studied.Three supercell interface models of WC-Co/cBN4B,WC-Co/Diamond/cBN4B and WC-Co/SiCSi-C/Dia-mond/cBN4B were established,the interface bonding works and bond length distributions at different deposition temperatures(1023K,1073K,1123K,1173K,1223K,1273K,1323K)were calculated and analyzed by molecular dynamics simulation.The analysis and research results show that within the temperature ranges studied in this paper:the most suitable deposition temperature of cBN coating on WC-Co matrix is 1223K for the cBN coated carbide tool without interlayer;the cBN coating and Diamond interlayer were deposited on the WC-Co substrate,the most suitable deposition temperature is 1173K for cBN coated carbide tools with Diamond single interlayer,and for the cBN coated carbide tools with SiC/Diamond double interlayers,the most suitable temperature for depositing interlayers of SiC and Diamond on WC-Co substrate is 1173K,moreover the most suitable temperature for depositing cBN coating on Diamond is 1223K.