| Unbalanced magnetron sputtering was used to deposit Ni-CrSiN coatings with various Ni contents on Ti6Al4V and single crystal Si substrates.X-ray diffractometer,X-ray photoelectron spectroscopy and scanning electron microscopy were used to analyze the crystal phase structure,composition and valence state,as well as the surface and cross-section morphology of the coatings,respectively.Then the roughness and residual stress of the coatings was characterized by a white light interferometer,the adhesion was characterized by a scratch tester;the hardness and toughness were obtained by dynamic ultra-micro hardness test analysis.The tribological properties of the coatings in seawater were tested using a ball-disk friction and wear tester,and the wear scars were analyzed by a white light interferometer and a scanning electron microscope equipped with an energy dispersive X-ray spectrometer to study the friction and wear mechanism of the coatings.Finally,the three-electrode electrochemical workstation was used to test the open circuit voltage,electrochemical impedance spectroscopy and polarization curve of the thin coatings in seawater,and the results were fitted and analyzed.X-ray diffractometer,X-ray photoelectron spectroscopy and the scanning electron microscope with energy dispersion X-ray spectrometer were used to analyze the corrosion mechanism of the coatings.（1）The content of Ni in Ni-CrSiN coatings increased from 0at%to 13.9at%,while the NiCr target current increased.Doping of Ni promoted the preferential growth of Cr N crystals along（200）.The nanocomposite structure of the coatings was Cr N crystal surrounded by the amorphous a-SiNx and elemental Ni,and the surface roughness of the coatings reduced when more Ni was added.The doping of Ni improved the toughness,meanwhile the coatings maintained a good hardness at a low doping amount.When the doping amount of Ni was 5.2at%,The Ni-CrSiN coatings had an excellent combination of hardness and toughness.The hardness value was 28.6 GPa and the toughness value was8.05 MPa·m1/2.Excessive Ni doping（≥10.8at%）made the coatings have higher toughness,but its hardness was poor（20.1 GPa and 24.5 GPa）.（2）A small amount of Ni doping（2.4at%～8.3at%）extended the running-in period of Ni-CrSiN coatings,otherwise the running-in period was shortened.Doping of Ni made the coatings have typical friction stabilization period.Ni doping would not reduce the friction coefficient of the CrSiN coatings,but it protected the grinding ball and reduced its wear rate.When the doping amount of Ni element was5.2at%,The coatings had the best combination of hardness and toughness,which made its wear rate be the lowest(8.5×10-8 mm3/Nm)and the wear resistance be the best.During friction,Si C balls underwent a hydration reaction to form a colloidal soft lubricating layer（Si（OH）4）with antifriction effect,which reduced the average steady state friction coefficient of all coatings.The coating with Ni content of10.8at%due to the optimal plastic deformation ability had the highest average steady state friction coefficient（0.211）,other coatings with Ni content had similar average steady state friction coefficients（0.165-0.171）.During the grinding process,both the Ni-CrSiN coatings and the Si C pellets suffered frictional chemical wear,resulting in oxidation products such as Cr2O3 and Si O2.These oxide abrasive particles damaged the coatings,forming furrows,and abrasive wear occurred.（3）The doping of Ni reduced the open circuit voltage of CrSiN coatings and increased the possibility of coatings corrosion.The doping of Ni increased the resistance of the top coatings Rtl,the overall resistance Rbl of the Cr/Cr N/CrSiN transition layer system,and then increased the charge transfer resistance Rct,so that the corrosion resistance of the coatings was improved.When the doping amount of Ni was 8.3at%,Ni-CrSiN coatings had the largest Rct（3.51×106Ωcm2）,and its corrosion resistance was the best.All coatings formed a Si Ox passivation layer during corrosion to improve corrosion resistance.And a certain amount of Ni doping（8.3 a.%～10.8at%）enabled the coatings to form a passivation layer containing Si Ox and Ni O during corrosion,further reduced the self-corrosion current densities（18.54 n A/cm2 and 18.16 n A/cm2 respectively）,which improved the corrosion resistance of the coatings;but excessive Ni element doping made the passivation layer of the the coatings more susceptible to pitting damage,which in turn affected the corrosion resistance of the coatings. |
