Study On The Surface Strengthening Of Strainless Steel And Its Tribological Properties

Stainless steel has been widely used in aerospace,chemical,metallurgy,marine and other fields,for its characteristics such as good corrosion resistance,obdurability and easy maintenance.Surface strengthening technology is a technology of applying surface engineering technology to modify or coating the surface of a component.It can strengthen the surface of the stainless steel so as to improve its tribological performance and prolong its service life.Metal chromium(Cr)has the characteristics such as high hardness,wear resistance and anti-friction performance.Carbon nanotubes(CNT)and graphene(graphene)have the characteristics such as high mechanical strength and good lubricating properties.They have become the typical nano-additive materials applied in surface strengthening.In order to improve the wear resistance and anti-friction performance of 420 stainless steel,a new composite electroplating technology was developed which combined the acidified multi-walled carbon nanotubes(MWCNT)and graphene oxide(GOS)with the hexavalent Cr.Cr based carbon nanomaterial composite coatings were prepared by composite electroplating technology and their wear resistance and anti-friction performance were studied.The details are as follows:1.GOS and acidified MWCNT were prepared by modified Hummers method and CNT acidification method,respectively.The morphology and structure of GOS and acidified MWCNT were characterized using scanning electron microscopy(SEM),transmission electron microscopy,Raman spectroscopy and Fourier transform infrared spectroscopy.The results showed that the existence of oxygen containing functional groups on the surface of acidified MWCNT and GOS.Then they were added to the plating solution respectively.The composite plating solutions containing GOS and acidified MWCNT were prepared by ultrasonic dispersion respectively.Finally,the composite coatings of MWCNT-Cr and GOS-Cr was prepared by co-deposition of metal Cr with different concentrations of acidified MWCNT and GOS respectively under different plating temperatures and current densities.2.MWCNT-Cr and GOS-Cr composite coatings were characterized by SEM.The results showed that the acidified MWCNT and GOS on the surface of the composite coatings can be observed obviously,which indicates that the metal Cr has been successfully co-deposited with the acidified MWCNT and GOS.3.The hardness,wear resistance and anti-friction performance of the composite coatings were characterized,and the effects of current density,electroplating temperature and the concentration of carbon nanomaterials on the hardness,wear resistance and anti-friction performance of the composite coatings were studied.The results show that:(1)The hardness of the pure Cr coatings,MWCNT-Cr and GOS-Cr composite coatings increased with the increase of current density and carbon nanomaterial concentration and increased with the decrease of plating temperature.The hardness of the composite coatings was always slightly higher compared with pure Cr coatings;(2)The friction coefficients of the pure Cr coatings,MWCNT-Cr and GOS-Cr composite coatings decreased first,then increased with the increase of current density,plating temperature and carbon nanomaterial concentration.The friction coefficient of the composite coatings was always slightly lower compared with pure Cr coatings;(3)The wear loss of the pure Cr coatings,MWCNT-Cr and GOS-Cr composite coatings decreased with the increase of current density and carbon nanomaterial concentration and decreased with the decrease of plating temperature.The wear loss of the composite coatings was always lower compared with pure Cr coatings.In conclusion,the hardness of Cr based carbon nanomaterial composite coatings was higher than that of pure Cr coatings.The friction coefficient and wear loss of Cr based carbon nanomaterial composite coatings were lower than that of the pure Cr coatings,which indicated that the acidified MWCNT and GOS had a good strengthening effect on the composite coatings for their high mechanical strength and super-lubrication performance.