| As the core component of high-speed precision presses,ball head service performance directly affects the working accuracy,efficiency and life of the press.The friction wear and corrosion resistance of the ball head of the press directly affect its service performance.In this paper,TiN coating and AlCrN coating are deposited by multi-arc ion plating process on the basis of gas nitriding on the surface of the ball head to improve their surface wear resistance and corrosion resistance,and the main work and conclusions of this paper are as follows:(1)Gas nitriding is used to surface strengthen the ball head of the press.The optimal process parameters are:nitriding temperature 550℃,nitriding time 5.5 h,nitriding pressure 80 Pa.The average thickness of the nitriding layer was 174.52μm,the average hardness was 520.4 HV0.025,and the surface roughness Ra was 0.461 μm,which provided matrix preparation for the preparation of the surface coating of the ball head of the press.(2)Using multi-arc ion plating technology,TiN coating and AlCrN coating are applied to the surface of the ball head of the press.The preparation process parameters of TiN coating are:vacuum degree 8.8×10-3 Pa,matrix temperature 400℃,nitrogen flow rate 370 sccm,matrix bias 65～80 V,deposition current 130 A.The average thickness of the TiN coating was 2.7μm,and the diffraction peaks of(111)and(200)of TiN and the(300)diffraction peak of Ti2N were detected,with an average hardness value of 1363.5 HV0.025.The preparation process parameters of AlCrN coating are:vacuum degree 9.2×10-3 Pa,matrix temperature 380℃,nitrogen flow rate 680 sccm,matrix bias 100～115 V,deposition current 155 A.The average thickness of AlCrN coating was 2.3 μm,and the diffraction peaks of CrN(111),(200)and(220)were detected,and the average hardness value was 2856.9 HV0.025.(3)The friction and wear properties of the ball head of the press after composite treatment were studied.Under low load conditions,Si3N4 ceramic balls were selected as the grinding pair,and 2 N,4 N and 6 N loads were used for experiments,and the wear rates of TiN samples treated with composite treatment decreased by 38.9%,51.8%and 59.1%respectively compared to the substrate.The wear rate of AlCrN samples treated with composite treatment decreased by 50.0%,56.1%and 61.3%respectively compared to the substrate.Under high load conditions,the friction pair of small pin disc was selected and the loads of 100 N,200 N and 300 N were used for experiments,and the wear amount of TiN samples treated with composite treatment decreased by 60.4%,56.3%and 57.6%respectively compared to the substrate.The wear amount of AlCrN samples treated with composite treatment decreased by 80.7%,66.9%and 65.5%respectively compared to the substrate.(4)The corrosion resistance of the press ball head after composite treatment was studied using GAMRY ESA410 electrochemical workstation.The corrosion current densities of AlCrN,TiN,nitriding and ball head matrix samples were 0.96 μA·cm-2,1.09 μA·cm-2,2.44μA·cm-2,and 8.96 μA·cm-2,respectively.The corrosion potentials of AlCrN,TiN,nitrided and ball head matrix samples were:-357 mV,-471 mV,-562 mV,and-622 mV,respectively.The composite treatment improves the corrosion resistance of the ball head.(5)The life test of the press ball head after composite treatment under actual working conditions.The ball head without any treatment failed at 6000 h,the single nitriding ball head failed at 7500 h,and the composite treated ball head coating fell off after 9000 h of work,and the wear of the TiN ball head coating was more serious than that of AlCrN ball head,but it can still be effectively used,indicating that the composite treatment can improve the service life of the ball head by more than 50%. |
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