| In this paper,Ni-Cr-N coatings were deposited on 42CrMo substrates via arc ion plating technology with the variation of element content,modulation period and sublayer composition.XRD,XPS,SEM,hardness tester,electrochemical workstation and corrosive wear tester were applied to investigate the effect of these factors mentioned above on chemical compositions,microstructure,mechanical properties,electrochemical corrosion and corrosive wear performances systematically.The conclusions were summarized as follows:(1)NiCrN coatings with different element contents were prepared by means of manipulating target compositions.The results showed that NiCrN coatings were mainly composed of metallic Ni,Cr2N and CrN ceramic phases.With the increase of Ni content,the adhesion strength was improved,while the microhardness decreased from 759HK0.025 to 566 HK0.025.NiCrN coatings exhibited the higher corrosion potential and lower corrosion current densities compared to those of the substrates based on the potentiadynamic polarization,indicating the better corrosion resistance.The coating mass loss rate firstly decreased,and then increased with increasing Ni content according to the results of corrosive wear experiments.44.1 at.%Ni coating exhibited the minimum mass loss,only 7.54×10-3 g/cm2 after corrosive wear test for 16 h.Corrosive medium arrived at the coating-substrate interface and eroded the substrate preferentially by penetrated defects in the coatings which acted as the medium transport channels.Moreover,the synergistic effects between corrosion and wear accelerated the failure of the coatings.(2)The composition optimized Cr/NiCrN multilayer coatings with various modulation periods(from 1 to 15)were synthesized,and the results showed that NiCrN coatings were mainly composed of metallic Ni and Cr,Cr2N and CrN ceramic phases.With the increase of modulation periods,the adhesion strength kept almost at the same level(HF 2),while the microhardness increased from 882 HK0.025 to 964 HK0.025.The mass loss rate of Cr/NiCrN multilayer coatings decreased gradually with an increase in modulation periods based on the kinetic curves of corrosive wear experiments.Cycle-15 coating exhibited the minimum mass loss,only 4.14×10-3 g/cm2 after corrosive wear test for 16 h.Defects considered as weak locations would be destroyed preferentially in corrosive wear circumstances.Two kinds of failure models of multilayer coatings were illustrated here:as for the penetrated defects,the failure mechanism was similar to the singer layer,as for the non-penetrated defects,defects on the coating surface were destroyed perferentially,resulting in a decrease in coating thinning,and followed by the ruin of the substrate due to insufficient coating protection.(3)NiCrN multilayers with different sublayer compositions were deposited based on the optimization results of the NiCrN composition and modulation periods.Results showed that the adhesion strength of Cr/NiCrN,NiCr/NiCrN and Cr N/NiCrN multilayers maintained at the same level(HF 2),while the microhardness were variable,Cr N/NiCrN>Cr/NiCrN>Ni Cr/NiCrN.Moreever,Cr/NiCrN multilayer coating exhibited the minimum mass loss,only 4.14×10-3 g/cm2 after corrosive wear test for16 h,demonsrating the optimal corrosive wear resistance. |
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