High-speed Dry Cutting Performance of AlCrBN/AlTiN Multilayer Coatings with Various Thickness Ratios of Sublayers
Multi-arc ion plating is currently the most widely used physical vapor deposition method in the industry because of its high deposition rate,good film-substrate adhesion,and dense microstructure.The AlCrBN/AlTiN multilayer coatings with different thickness ratios of sublayers were prepared by arc ion plating and the effects of different thickness ratios on phase,hardness,wear resistance,and cutting performance were studied.YG8 cemented carbide inserts(16 mm×16 mm×6 mm)and YG8 cemented carbide sheet(50 mmx10 mmx1 mm)were used as substrate for the preparation of AlCrBN/AlTiN multilayer coatings by applying a new ion source-column arc-multi-arc coating equipment.The coating equipment consisted of the vacuum system,control system,and power supply system.The vacuum system consisted of a mechanical pump,a Roots pump,and a molecular pump,and the vacuum level could reach 1×10-5 Pa.The control system consisted of a PLC program,which was used for programming and controlling the process during the deposition.The vacuum chamber contained a cylindrical Ti target(φ 100 mm×850 mm)and four arc targets(φ160 mm× 15 mm),and there was a speed-adjustable turntable in the vacuum chamber for placing the samples to be deposited.The coating process consisted of four steps:heating,glow discharge,ion etching,and coating.The heating in the coating process was to remove the water vapor in the furnace and make the surface of the workpiece active.Glow discharge was to ionize Ar+ions to further remove water vapor from the furnace.Ion etching was used to clean the target and workpiece surface.The field emission scanning electron microscope(FESEM,MIRA3 XMU,TESCAN,Czechia)was used to observe the cross-sectional morphology.The phase composition of the coating was determined with an X-ray diffractometer with a scanning speed and angle range of 10(°)/min and 30° to 70°,respectively.Micro Vickers hardness tester was utilized and the multilayer structure of the coating cross-section was observed by a ball-crater tester.The ball-disc friction tester(UMT Tribolab,BRUKER,USA)was used to perform reciprocating cyclic sliding of alumina balls(Al2O3).Dry cutting performance test was conducted to coatings without lubrication by TAIWAN TAKISAWA LA-150 lathe.The AlCrBN/AlTiN multilayer coatings with different thickness ratios of sublayers were prepared by arc ion plating.The 2∶1 thickness ratio was the best experimental preparation process parameter.The coating phase compositions were fcc-(Cr,Al)N and fcc-(Ti,Al)N.The coating structure became denser with increasing sublayer thickness ratio.No new phase was generated in AlCrBN/AlTiN multilayer coatings with different thickness ratios of sublayers after annealing at various temperatures,and the interfaces between sublayers also gradually disappeared.The AlCrBN/AlTiN with a thickness ratio of 2∶1 had the best wear resistance.The best high-speed dry cutting performance was obtained from AlCrBN/AlTiN with a thickness ratio of 2∶1 at both cutting speed of 100 m/min and 150 m/min.The composite structure composed of nanocrystalline phases covered with a thin layer of the amorphous BNx phase is the main reason for the significant improvement in wear and cutting performance.This kind of composite structure can improve the hardness and high temperature performance of the coatings.
AlCrBN coatingmultilayer coatingfriction and wearhigh-speed dry cutting
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