Study On The Structure And Properties Of AlCrSiN-based Self-lubricating Tool Coatings

With the rapid development of modern high-performance material preparation technology,the number of various components and parts of difficult materials is increasing,In particular,the advent of advanced machining technologies such as high-speed cutting,high-efficiency machining,and dry cutting has continuously raised higher requirements for cutting performance of tools.Applying a hard wear-resistant coating on the surface of the tool as an effective method to improve its service life and processing efficiency.At present,the AlCrSiN coatings widely used in the tool industry,and have excellent mechanical properties,such as high hardness,large elastic modulus,good toughness,and strong adhensive strength.However,the coating has a large friction coefficient,and a large amount of cutting heat is generated during the machining process,resulting in severe tool wear and reduced machining quality.If the sixth subgroup Mo element is doped in the AlCrSiN coating,the Mo element is often oxidized into a layered MoO₃ with a low shear modulus during the friction process.Shear slippage between the layers can give the coating a good lubrication function.It is expected to improve the friction and wear performance of the coating;At the same time,if Mo atoms are solid-dissolved into the?Al,Cr?N lattice,it can also cause lattice distortion to achieve strengthening and further improve the performance.In view of the above,the effects of CrMo target sputtering power,deposition pressure and other process parameters on the microstructure,mechanical properties and tribological properties of the AlCrSiN/Mo self-lubricating coating were systematically studied by using hybrid magnetron sputtering technology,The coating was further strengthened by vacuum heat treatment,and its heat resistance was evaluated.According to the above studies,the deposited and annealed AlCrSiN/Mo coatings were deposited on the surface of carbide end mills,respectively,and the cutting performance was compared with that of AlTiN coated milling cutters and Balzers G6coated milling cutters.The specific research work was as follows:The number and kinetic energy of the sputtered particles are changed by adjusting the CrMo target sputtering power,and the composition and microstructure of the coating have been controlled.It has found that the organization of the AlCrSiN/Mo coating was composed of fcc-?Al,Cr?N phase and c-Mo₂N phase.As the CrMo target sputtering power increasing,the preferred orientation gradually changed from?200?to?111?crystal phase,and the surface morphologies have showed a triangular pyramid structure,and corresponding columnar crystal size kept increasing;the friction coefficient gradually decreased to 0.56;the adhensive strength were all higher than 150 N.When the CrMo target sputtering power was 0.6 kW,the mechanical properties and wear resistance were excellent,the characteristic values of H/E and H³/E*² were highest,the hardness was about 16.8 GPa,and wear rate was 1.62×10^-3?m³/N·?m.The average free path of sputtered particles can be changed by the deposition pressure in the chamber,which affects the composition,structure and properties of the coating.The organization of the AlCrSiN/Mo coatings were composed of fcc-?Al,Cr?N phase and c-Mo₂N phase and grains show a fine fibrous structure,which prepared by different deposition pressure.With the increasing of deposition pressure,the particle clusters increased and have obvious crystallographic characteristics;the deposition rate decreased gradually;the adhensive strength increased from 65.6 N to 81.9 N gradually.When the deposition pressure was 1.6 Pa,the hardness and modulus of elasticity,both of characteristic values of H/E and H³/E*² reached the highest,which have shown a good antifriction and wear resistant performance.In order to further increase the crystal content in the AlCrSiN/Mo coatings,and promote the crystallization and grain growth,annealing treatment can be used to strengthen the coatings.Compared with the as-deposited coatings,the diffraction peak of the?200?crystal plane was significantly enhanced;the internal stress was significantly increased;and the tribological properties were significantly improved.As the annealing temperature increased,the fcc-?Al,Cr?N phase gradually decomposed into hcp-AlN phase and hcp-Cr₂N phase.The optimized optimal vacuum heat treatment temperature was 800?.The optimized parameters were used to prepare the deposited and annealed AlCrSiN/Mo coatings on the surface of the end mills,and the cutting performance was compared with that of the AlTiN coated milling cutter and Balzers G6 coated milling cutter.The study found that after continuous dry cutting of hardened steel?>55 HRC?,the cutting temperature of the AlCrSiN/Mo deposited coated milling cutter was the lowest,about575.3?,and the service life was longer,about 44 min.Corresponded to the best chip integrity and the surface quality of the workpiece was optimal.