| The fast development of modern manufacturing industry promotes requests for higher cutting speed and higher machining efficiency.The wide application of difficult-to-cut materials also calls for higher performance of cutting tools.The coated cutting tools combine the advantages of high wear resistance,excellent oxidation resistance of hard coatings and high strength and toughness of tool substrates,which improves tool machinability,surface quality of the workpiece,and reduces the machining cost.AlCrN coating has been widely used in cutting tool field due to excellent high temperature oxidation resistance and good toughness.However,due to its relatively low hardness,it does not meet requirements of processing hard-to-machine materials.AlTiSiN coating exhibits superior hardness.However,it could not meet the requirements of machining hard-to-cut materials due to its poor oxidation resistance.Therefore,combining with excellent oxidation resistance of AlCrN coating and superior hardness of AlTiSiN coating,we propose the investigation on fabriction and properties of AlCrN/AlTiSiN nanolayered coatings.Firstly,the AlTiSiN and AlCrN monolayer coatings with the best performance were obtained by optimizing the deposition parameters,and then AlCrN/AlTiSiN multi-layer coatings were designed and fabricated by rotating substrates.The effects of substrate bias,nitrogen flow rate,modulation period on the microstructure,mechanical properties,high-temperature oxidation resistance,tribological properties and cutting performance of the AICrN/AlTiSiN nano-layered coatings were studied.The following results were obtained:(1)The micro structure and properties of the nanolayered AlCrN/AlTiSiN coatings was affected by the nitrogen pressure,bias voltage and modulated structure of the nano layers.By optimization of micro structure of the nanolayered coatings,the hardness,high-temperature oxidation resistance,thermal stability of the coatings was significantly improved.The nanolayered coatings exhibited higher hardness than the single coatings.At 800-1000?,the AlCrN/AlTiSiN nanolayered coatings have better oxidation resistance and higher thermal stability than the AlCrN and AlTiSiN coatings.(2)The tribological properties of AlCrN,AlTiSiN monolayer coatings and AlCrN/AlTiSiN multi-layer coatings at 25?,500? and 800? were compared,it was found that AlCrN/AlTiSiN multi-layer coatings exhibited better tribological properties compared with AlCrN and AlTiSiN caotings at different temperatures.At 800?,AlCrN and AlTiSiN coatings exhibited severe adhesion wear and oxidation wear,respectively.While the worn surface of AlCrN/AlTiSiN multilayer coating was relative smooth,and formed a dense Al2O3 tribofilm.This Al2O3 film has low shear strength and acts as a self-lubricating layer,thereby significantly reducing the friction coefficient and the wear rate.(3)The cutting performance of AlCrN,AlTiSiN coatings and AlCrN/AlTiSiN multilayer coatings were compared.During the cutting SKD11 and Ti6Al4V,It has been found that AlCrN/AlTiSiN multilayer coated tool has longer cutting life and better surface quality compared with AlCrN,AlTiSiN coatings,which exhibits an excellent cutting performance.The cutting life of AlCrN/AlTiSiN multilayer coated tool was 4,2.8 and 2 times longer than that of the carbide tool,AlCrN and AlTiSiN coated tools,respectively.(4)The antifriction mechanism of AlCrN/AlTiSiN coated tool is discussed.The good wear resistance of AlCrN/AlTiSiN multilayer coated tool is the best from four factors:The high hardness of the coating is improved by the multilayer structure,and improves the abrasion resistance of the tool;The good oxidation and thermal stability promote mechanical property of the tool;The multilayer structure enhances the adhesion resistance of the coating,which improves the adhesion resistance wear of the tool;In the cutting process,the multilayer structure improves peeling resistance of the coatig,which further promotes the tool life. |
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