Microstructure and tribological performance of TiN/DLC and NiN/DLC coatings
Diamond-like carbon(DLC)coatings with TiN and NiN as transition layers were deposited on 316L stainless steel substrate using magnetron sputtering deposition technology.The surface quality,microstructure and tribological performance of the DLC coatings were analyzed by means of scanning electron microscopy,Raman spectroscopy,nanoindentation tester,scratch tester and friction and wear testing machine.The results show that there are many deposition defects such as particles and pores on the surface of NiN/DLC coating,and when Ni and N are co-deposited as intermediate transition layers,Ni mostly exists in the form of metallic elements between DLC and substrate.Due to the structure of the metallic substrate and the presence of Ni,the interface matching between substrate and transition layer is improved,resulting in high bonding strength of the NiN/DLC coating and substrate,with a bonding force of 14.91 N.However,when Ti and N are co-deposited as a transition layer,Ti and C combine to form metal carbides that exist between DLC and the substrate,which is beneficial for improving the coating density(1.929 g/cm3)and hardness.Moreover,the formation of high hardness metal carbides is beneficial for improving the deformation ability of the coatings,facilitating the amorphization of DLC structures,and promoting the formation of sp3-C bonds.Friction and wear analysis shows that under dry friction,deionized water,or weak acid(pH=5.6 HCl solution)conditions,the NiN/DLC coating has poor resistance to friction and wear and corrosion due to its low hardness and low density of microstructure.However,the TiN/DLC coating has lower friction coefficient and wear mass,and excellent wear and corrosion resistance.The above experimental analysis shows that nitrides and carbides of Ti with higher hardness as transition layers can better improve the microstructure and friction and wear performance of the DLC coatings,while Ni as transition layer can effectively improve the bonding strength of the NiN/DLC coating,but the coating is prone to detachment and failure during friction.
diamond-like carbon coatingfriction coefficienthardnessbinding forcewear mass loss