Study On The Preparation And Properties Of CrN And Cr-Nb-N Coatings On 40Cr Steel

Because of its excellent comprehensive mechanical properties,40 Cr steel is widely used in aerospace,automobile,machinery manufacturing and other fields,often used in the manufacture of automotive engines,automotive bearings and other parts.These parts need to withstand contact,impact,bending and other multiple stresses in the service process,resulting in reduced service life and even failure.In this paper,CrN and Cr-Nb-N coatings were deposited on the surface of 40 Cr steel by radio-frequency magnetron sputtering technology in order to extend service life of the parts.The microstructure,composition and morphology of the coatings were studied,and the effect of the two coatings on the mechanical properties and corrosion resistance of 40 Cr steel was explored.In this paper,CrN coatings were prepared with different substrate bias and the effect of substrate bias on the structure and properties of the coatings were studied.XRD and TEM results show that the CrN coating has a face-centered cubic structure,and the orientation of CrN coating changes from(111)to(200)when the substrate bias increases from 0 V to-50 V.When the substrate bias is-100 V,the CrN coating is composed of spherules with a diameter of5 ～ 8 nm.The XPS results show that the chemical bond of CrN coating is mainly Cr-N bond.The results of SEM and AFM analysis show that the deposition rate of CrN coatings decreases gradually with the increase of substrate bias,and the surface roughness first decreases and then increases.The mechanical properties test results show that the hardness,elastic modulus,filmbase binding strength and wear resistance of CrN coatings prepared at-100 V is the highest.The hydrophilic and hydrophobic test results show that CrN coating is hydrophobic,and the hydrophobic property makes CrN coating have better corrosion resistance.The electrochemical test results show that the CrN coating prepared at-100 V has the best corrosion resistance.In this paper,the Cr-Nb-N coatings were prepared by changing Nb/Cr,and the effect of Nb/Cr on the structure and properties of the coatings were studied.XRD and TEM results show that the crystal structure of Cr-Nb-N coating is the same as that of CrN coating,and the introduction of Nb forms Cr-Nb-N solid solution.When Nb/Cr increases from 1:10 to 2:10,the orientation of Cr-Nb-N coating changes from(111)to(200).When Nb/Cr is 3:10,the Cr-Nb-N coating is composed of spherules with diameter of 2 ～ 4 nm.The XPS results show that the chemical bonds of Cr-Nb-N coating are Nb-N and Cr-N.The SEM and AFM results show that the coating is closely bound to the substrate,and the surface roughness first decreases and then increases with the increase of Nb/Cr.Compared with CrN coating,the deposition rate and surface roughness of Cr-Nb-N coating decrease.The mechanical properties test results show that when Nb/Cr is 3:10,the hardness,elastic modulus,film-base binding strength and wear resistance of Cr-Nb-N coating reach the highest,and the mechanical properties of Cr-Nb-N coating are obviously improved compared with 40 Cr steel and CrN coating.The presence of Cr transition layer can significantly increase the bonding strength between Cr-Nb-N coating and40 Cr steel.The hydrophilic and hydrophobic test results show that Cr-Nb-N coating is hydrophobic.The electrochemical test results show that when Nb/Cr is 3:10,the Cr-Nb-N coating has the best corrosion resistance,which is better than that of CrN coating.